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Posted by: wayne1234 Jan 22 2010, 11:23 PM

Ok dual webber carbed 2.0, I think the PO had the head vents running to a T then to the oil breather near the oil cap... Is this right?? I did a search and now I'm really confused,,,,

Posted by: Cap'n Krusty Jan 22 2010, 11:47 PM

Dumb. No, make that stupid. What ever possessed him to vent the engine into itself? Yes, you need a breather box, even though it's illegal by Fed law. Vent the box ionto one or both air cleaners, so it at least looks legal. It's probably a leaker, and proper ventinmg should take care of that unless the seals are blown. The Cap'n

Posted by: wayne1234 Jan 23 2010, 12:05 AM

This is a completly rebuilt engine I am just putting it back in the car now, setting up things, and it didnt seem right,,, is there a how to or a write up I couldnt find anything straight forward when I searched... Thanks

Posted by: rick 918-S Jan 23 2010, 12:22 AM

Someone will have photos for you. I wish I were as smart as the capt. I could try to draw it out for you but stick men won't due in this instance. Best wait for someone else.

Posted by: Racer Chris Jan 23 2010, 05:30 AM

This is an install pic of the Tangerine Racing Breather Can that incorporates the features Cap'n Krusty recommends.

Both heads and the crankcase are vented to the cylindrical canister.
The canister is designed to effectively separate any oil from the vapors and return the oil to the engine via a bottom drain hose.
The top of the canister is connected to both air cleaners so all the vapors are integrated with the engine intake air.
Therefore no atmospheric contamination or oil mist in the engine compartment.

Posted by: Cevan Jan 23 2010, 07:29 AM

I've seen these arrangements setup a couple of different ways; either venting the vapor back to the top of the carb air filters (like the photo above) or out thru a small filter into the engine bay. I like Chris' setup in that there's no oil vapor escaping into the engine bay and making every speck of dust stick to the motor.

Is it necessary to use the spark arrestor that the stock D-Jet uses to tie the two nead vents together before venting to the cannister?

Posted by: Racer Chris Jan 23 2010, 08:37 AM

Much better to go directly to the can, at least with ours.

Posted by: Gint Jan 23 2010, 09:06 AM

http://www.914world.com/bbs2/index.php?act=Search&CODE=show&searchid=684deeaf13b281055102469432827cdb&search_in=posts&result_type=topics&highlite=%2B%2Bhead+%2Bvent

A search for +oil +breather will yield lots of previous threads on the subject also. Here you go...

http://www.914world.com/bbs2/index.php?act=Search&CODE=show&searchid=4127f8430219aa257407504316267874&search_in=posts&result_type=topics&highlite=%2B%2Boil+%2Bbreather

Posted by: pbanders Jan 23 2010, 10:20 AM

Note that even the Tangerine solution, which is the best one I've seen for carb setups, doesn't provide the same function as the factory system does. The factory system is a true Positive Crankcase Ventilation (PCV) system, that uses intake manifold vacuum to scavenge crankcase vapors. The Tangerine system (and other passive breather systems) depend on crankcase pressure alone to transport vapor to the system. The factory system uses an active PCV Valve mounted on the oil filler box to manage the system across a wide range of intake manifold pressures and crankcase pressures. There's a writeup on this system at my web page below.

Posted by: ME733 Jan 23 2010, 01:45 PM

[quote name='pbanders' date='Jan 23 2010, 11:20 AM' post='1264867']
Note that even the Tangerine solution, which is the best one I've seen for carb setups, doesn't provide the same function as the factory system does. The factory system is a true Positive Crankcase Ventilation (PCV) system, that uses intake manifold vacuum to scavenge crankcase vapors. The Tangerine system (and other passive breather systems) depend on crankcase pressure alone to transport vapor to the system. The factory system uses an active PCV Valve mounted on the oil filler box to manage the system across a wide range of intake manifold pressures and crankcase pressures. There's a writeup on this system at my web page below................. .....THE INTERIOR of the air filter housing will have a negative pressure as the carburators....SUCK AIR. Therefore the tangerine system will work identical to the factory setup, providing positive crankcase ventilation....and as venting the crankcase is important, reguardless of RPM,s why would anyone want or need a pvc valve?. The easier the engine "breaths" the faster it will rev. up., and have (fewer leaks) which are mostly caused by excessive crankcase pressure. A very free breathing engine starts with some internal crankcase modifications. Murray

Posted by: pbanders Jan 23 2010, 03:35 PM

The interior of the filter area of an air filter system like the Tangerine system (common to all Weber/Dellorto systems) is not at low pressure, it's essentially at atmospheric pressure. Yes, there is a tiny pressure differential across the filter element (less than 5 mbar), but if the pressure difference was truly significant, you'd be choking the breathing of the engine. True low pressure is in the area below the throttle plates, in the case of a carb'ed setup, in the runners themselves. Note that this is true only in the case of closed throttle (idle) or part-load (low throttle angle) conditions. When the engine is at WOT, there's only about 20 mbar of difference between the local atmospheric pressure and the pressure below the throttle plate.

True positive crankcase ventilation requires manifold vacuum.

PCV valves operate to control the amount of manifold vacuum used for crankcase scavenging. If you simply hook up manifold vacuum to the crankcase, you've essentially opened a giant vacuum leak. Even if the crankcase is completely sealed, too much vacuum can have other negative effects. The PCV valve controls the vacuum level in the crankcase to avoid these issues.

Posted by: wayne1234 Jan 23 2010, 08:54 PM

Man I hate to say it but the setup going back into the carb filter tops doesnt look very good,,, kinda cluttered,,, I know it sounds kinda vain but I would like a clean looking setup that would keep oil off the engine,,

Posted by: Racer Chris Jan 23 2010, 10:35 PM

This is our original design that has all the same features except the carb suction.
A cheaper product is available from CB Performance that uses a small rectangular box instead of the cylindrical can.
IMO, the volume of the can is critical to effective cranckcase ventilation, and the oil separation features we employ do a much better job of preventing oil mist from contaminating the engine compartment.
If you follow the links Gint provided I'm sure you'll see someone's installation of the CB product.

Posted by: ME733 Jan 24 2010, 07:24 AM

.....................Well you have already explained the situation, and apparently do not understand what your information contains. 1. there IS very little vaccum in the air cleaner. However IF the crankcase pressure IS excessive (like W.O.T.) the pressure WILL be routed to the air cleaner, and there being a (very low negative pressure) WILL be drawn down the carburators....2. With the example you provided...Manafold vaccum...provides...giant vaccum leak...without P.V.C. valve...this is somewhat true. The manafold, runner, which has the vaccum line...will result in THAT PARTICULAR CYLINDER running LEANER/with contaminants/oil.water vapor/hot crankcase air,etc....3. IT is much better to divide /split the crankcase air/vapors/ into ALL the cylinders. This will enable a far more accurate adjustment of /carburator adjustments/JETS to provide optimum performance.3. the possability of having too much vaccum is (O) zero....MURRAY.

Posted by: Cevan Jan 24 2010, 08:06 AM

There being a ton of people on this forum running carbs, I'd like to know how your breather is routed (to the carb filters or to the atmosphere via a small air filter). If you route to the carbs, do your carbs stay clean or does the oil vapor gum things up? If you route to the atmosphere, does the vapor dirty the engine bay?

Posted by: r_towle Jan 24 2010, 10:00 AM

Cevan,

If you run the oil vapors into the carbs, its much cleaner in the engine bay, period. I will say the net result for me and my personal issue is that I have less oil in the engine bay now...but I found a leaking head vent tube while installing the system...

With the exit gases routed to the carbs, I have this opinion.
The drawback that IC is that now you are once again introducing oil into the A/F mixture which makes the burn less efficient. Spark plugs dont like oil, and IMHO you loose HP.

If you use the original setup Foley makes yet run a hose from the top vent and relocate the exit of that vent somewhere outside of the engine bay, you will get the best of both worlds...

Do not vent it in front of a wheel...oil vapor on one wheel would be bad.

Older american cars just ran a hose with no filter down underneath the car and used the venturi affect to suck the vapors out of the hose.

From personal experience, I just installed the EMPI/CB performance unit and I mounted it right in front of the motor, centered like Foley shows his.
Well, guess what is right next to it. The electrical intake heater fan...
This setup now sucks crankcase vapors (which are not just oil but blowby gases) into the passenger compartment...
I was good for one trip to work and back...now I need to change the output. Headache, CO levels to high and I drove to work and back with the windows open in the winter...not a good setup.

The EMPI/CB performance unit has a raised lid that allows the gases to escape all around the lid. I plan to mill off the raised standoffs and close the lid tight, then add a NPT pipe fitting to the top and remote locate a filter outside the engine bay....somewhere...dunno where.

I wont shoot the vapors into the carbs, I need every spec of HP the little powerplant can produce and IC no logic in adding oil to the mix. My car will never be a green planet saver, nor will it single handedly deplete the ozone layer.

I have all my DD cars running modern FI with all the restrictions. the 914 is a toy and is driven as a hobby car.

Rich

Posted by: Racer Chris Jan 24 2010, 11:17 AM

That could be a problem with the CB product which doesn't have effective oil separation features. Escept on engines that have excessive blowby from worn or poorly seated rings my system is designed to nearly eliminate oil from ever escaping the engine.
Beside that, a healthy engine will produce far less crankcase gasses than the total amount of air entering the carbs. The amount of oil contained in the mix won't negatively influence combustion.

Posted by: pbanders Jan 24 2010, 11:29 AM

There's a significant difference between passive crankcase ventilation and active crankcase scavenging. The use of crankcase pressure (passive ventilation) as you describe was how it was done on carb setup cars for decades before 1970. Two factors drove manfacturers to adopt scavenging, oil sludging and post-1970 emissions regulations. PCV systems significantly reduced crankcase-based hydrocarbon emissions, and also did a much better job of removing water vapor from the crankcase than the old passive breather systems, resulting in less sludging and corrosion of internal engine components.

You point out the difficulty of incorporating a proper scavenging system when you have 4 separate intake runners with a carb setup, yet another reason that setups like this started to disappear after 1970. Nobody is advocating using a PCV system with a dual Weber setup, it would be very difficult to engineer. The best you can do is with a breather system.

Posted by: wayne1234 Jan 24 2010, 10:53 PM

ok how about this.. I know an my Audi TT a common "upgrade" is a oil catch can, many people use a air compressor water seperator bulb ... could you use one of these and just route th other side to atmosphere?

Posted by: kg6dxn Jan 24 2010, 11:24 PM

You could do what the V8 drag racers use. Crank case vacuum scavenger tubes welded to the exhaust. They create negative pressure in the crank case and help to seat the rings better and reduce blow by. This setup is not legal to run on the street but know one really checks for this set up. To use it correctly you will need check valves on the scavenger tubes. You would also run a sealed case, no vents other than the valve covers.

Posted by: ME733 Jan 26 2010, 08:20 AM

.....................well you have brought up another way to vent the crankcase, which has been used. I disagree that this system helps to "seat the rings"..it,s an old wifes tale. Rings seat, or not, based on assembly, type,cylinder wall preperation, type rings,and poor/or good assembly techniques,among other factors, etc., and if there is negative crankcase pressure..it would tend to increase ring blowby not reduce it. I Have used , the (negative pressure) crankcase ventelation, to exhaust system...collector...on race engines in the past.(quite a few years ago). The problem with a stock exhaust system (on the 914) is there is no collector .(except the bursche) and it,s too far away.(a plumbing zoo).routing to just one cylinder exhaust tube would be the solution, but not very effective. The essence of this system is that it CAN create NEGATIVE crankcase pressure. this too can cause engine leaks, valve cover seal problems, etc. The best installation is to have an open -to the atmosphere-vent for the crantcase itself. (some v-8s) have valve cover "breathers". Replacing the filler cap, on a 914,(or something similar) with a filtered, screened cap would probabley work, or a filtered breather hose connected to the filler box, just something to help,equalize the the crankcase pressure...when routing to the exhaust system. Murray

Posted by: johnnie5 Jan 26 2010, 09:56 AM

Here are a few pics of my CB/Empi setup.... seems to work fine for me.


Attached image(s)

Posted by: Cap'n Krusty Jan 26 2010, 11:06 AM

Rich Towle said earlier, "Older American cars just ran a hose with no filter down underneath the car and used the venturi affect to suck the vapors out of the hose."

That's true. In 1965, it became illegal to run a "road draft tube"in the United States, and it remains illegal today. Just because something "looks messy" isn't justification to choose the laws you wish to obey. Many of you are too young to remember what REAL smog was, and you should thank the "powers that be" for reducing it to the level it is today. While Los Angeles is fabled to have been (and still is, for many people) the epitome of smog, it's far from it. Try Denver, the San Francisco Peninsula, and Phoenix. I grew up in LA County, and I remember well experiencing whole summers where there were maybe 3 days of somewhat clear, safe, breathable air. Now there may be 3 really bad days in the entire summer. Those of you who think YOUR car won't make a difference, and YOUR personal tastes supercede the will (and the right) of the rest of us to have a clean environment, should rethink your role in society. End of Rant.

The Cap'n

Posted by: Gint Jan 26 2010, 12:41 PM

While I understand your point John and I agree with you, your facts with regard to polluted cities are in dispute.

http://www.citymayors.com/environment/polluted_uscities.html
http://green.yahoo.com/blog/daily_green_news/44/100-cities-the-best-and-worst-air-quality.html

Posted by: ME733 Jan 27 2010, 11:57 AM

...................I couldn't agree more. I grew up in ATLANTA georgia. As a kid it was all too common for cars to bellow smoke down the street, down the highway and down the expressway., sometimes to the extent it was dangerious to follow them.(much less the smell) And it was the obvious sign the car owner was a fool, and unconserned about anyone else. It,s just unfortunate that a few damn irrresponsable asses have forced all of society into the situation we find ourselves in today. Regulation of idiots,and everybody has to pay. The annual emmission inspections are a time consuming pain in the Ass and another cost of owning a car.I have never had a car fail Emmissions inspection but it,s still 2-3 hours out of your life ....for me waisted time, and 25.00 bucks.

Posted by: HAM Inc Jan 27 2010, 12:36 PM

Oil runs cooler and returns to the crankcase faster if you leave the heads unvented. BTDT, proved it on the street and the race track.

Posted by: DBCooper Jan 27 2010, 01:20 PM

Amen.

You really had to have been there to understand how bad it was. Here's a Tim Buckley album cover from the 70's, above and below the smog layer. You can make out the brown buildings down below. When you flew into town this is what you descended into:

Posted by: Cap'n Krusty Jan 27 2010, 01:58 PM

On some summer days in 1961, the air quality in Phoenix was poorer than Los Angeles. You have to remember that the photochemical components of smog aren't always present in the same quantities, but the other harmful components may still be there. I was in Denver in the summer of 1978 or 1979 for a swap meet at Storz Garage, and the smog was TERRIBLE! As for the SF Bay area, have you been there recently? Nasty.

I stand by my statements.

The Cap'n

Posted by: pbanders Jan 27 2010, 03:29 PM

The emissions issue is one of the main reasons I've stuck with D-Jetronic on my car and have worked to keep all of the emissions controls on it functioning properly. The '75-76 systems were even better for emissions, but were a stopgap measure on the way to the use of true three-way cat with O2 sensor mixture control, which came after the 914's demise.

Early D-Jet is still pretty good for emissions when properly tuned. Overrun fuel management, idle timing retard, fuel tank evaporative control and management, PCV system, and part-load mixture management all reduced emissions over the previous generation of cars.

Posted by: sean_v8_914 Jan 27 2010, 05:45 PM

just drive across the border and you will experience the difference our emmisions laws have made. I try to put everythnig in place on stock engines.
viva la EFI!

Posted by: bandjoey Jan 27 2010, 06:04 PM

OK. Up to here everything was making sense. Now I see this from HAM saying oil runs cooler with UnVented heads. ??? Please explain.

...and, Is this using a single line from the Oil Filler neck to a vent box and back to where? or no vent there either?

confused as usual.. Thanks

Posted by: jaxdream Jan 27 2010, 06:14 PM

I , too , was ok with this line of reasoning , untill this.??????????????????
I have 2 ( two ) 1.7 engines , one has head vents the other doesn't, I was planning on using the vented head engine as the direction of this thread was logical as to the evacuation of crankcase gases is helpfull to an extent , espeacilly on carbed engines , which is what I have on both of my 1.7's. Now that the head guy spoke up and said it didn't do jack for the engine , I want to hear more of this new info please, Len ???

Jack / Jaxdream

Posted by: Gint Jan 27 2010, 10:20 PM

Yeah, it used to get bad around here for a few days a year back then. But that one occasion was 30 years ago. In LA every day in 1978 or 79 probably looked like that. Your statement: is misleading at best. Actually it's just wrong. While it may be better today then it was 30+ years ago, LA is still worse than Denver, then and now.

Posted by: HAM Inc Jan 28 2010, 08:58 AM

It does do something; it slows the return of oil to the crankcase and therefore the pickup and it causes the oil to run a bit hotter.
I'm going to let you guys stew on this one for a while and see if you can figure it out. I'll give you a hint; it has to do with pressure differentials between the crankcase and rocker chambers.

Posted by: John Jentz Jan 28 2010, 09:31 AM

So, I should just put pipe plugs in the holes you drilled and taped in the heads you built for me? I guess development marches on, my heads are still in the boxes after 3 years! Maybe this year!

Posted by: luvatenor Feb 1 2010, 09:49 AM

Great info- Most of the info is for a two Carb setup. What about a single 2Bl Weber? Everything seems to have been removed from the engine compartment- just want to make it efficient and healthy- thanks

Posted by: underthetire Feb 1 2010, 05:03 PM

Actually, smog here is way better than LA. It is bad during fire season for sure though.
And my dads 57 tbird still has the road draft in it. First stupid smog check guy wanted him to drill a hole in his factory bird aluminum valve covers and install a PCV. Second guy smoged it no problem. Those valve covers in the condition they are in are worth 500-1000 bucks a pair!

Posted by: bandjoey Feb 1 2010, 11:35 PM

NO VENTS?

Posted by: jaxdream Feb 1 2010, 11:57 PM

Ok , Len I'll give it a shot ( I am not an engine rugu , probably never be , so I'm up for some learnin ).
Slow drain of oil back to the crankcase- less oil in the bottom for the pickup to pickup = hotter running engine with a lesser oil supply to run , hotter oil froths more causing cavitation and starvation to the oil pump( could this be the presure differential you mentioned ??) Would the small amount of oil up in the breather box and lines be that significant of an oil supply loss ??
Presure differential , hummmmmm...... I would dare to say that there is more presure in the crankcas area than the rocker box area , sucking the crankcase gases through the rocker box area will lessen the presure in the crankcase , but may increase the presure in the rocker box area =more of a chance that the pushrod tubes leak more as well as the rocker box cover gasket to leak more??

Or as some will say that I been into the rootcellar medicine too much , oh what the hell , a few shots won't hurt, much.

Jack / Jaxdream

Posted by: ME733 Feb 2 2010, 09:40 AM

,,,,,,,,,,,,,USE THE DAMN HEAD VENTS.........MURRAY.

Posted by: rhcb914 Feb 2 2010, 09:40 AM

Well if the oil is staying in the heads for a longer period of time and the heads are the hottest part of the engine it only makes sense that the oil is going to run hotter.

Now with unvented heads will the heads run hotter by not transfering as much heat to the oil?

Posted by: ME733 Feb 2 2010, 10:09 AM

..........USE THE DAMN HEAD VENTS.....Because, the lowest part of the head,s Is above the crankcase, oil level,...and ANY heat FROM, BY,or TRANSFERED to the head is going to be "captured". THE only way to dissapate this heat is from...air blowing accross the head from the cooling system, BLOWER....But another thing is going on. All the moisture(condension)( from oil above 212-degrees)...and airomatic gasses...fuel and blow-by contaminion is "trapped" in the head......Have you ever disassembled an engine with rusty film on the rockerarm covers?. rocker arms? ....IT,s due to low oil temperature, trapped condensation,and residuals.(airomatics-gas fumes) being trapped in the HEAD. The pushrod tubes equalize pressure in the head and crankcase. Therefore VENTING the heads is equivalant to venting the crankcase-only better as it,s also venting otherwise trapped-HEAT-moisture,and contaminants..............Murray.

Posted by: HAM Inc Feb 2 2010, 11:36 AM

Bingo! Now put some thought into why the oil spends more time in the rockerchambers on vented heads.


We have seen no evidence of this. The springs, the rocker arms and the interface between adjuster and valve tip are the only head components that rely on oil cooling. The heads generate way to much heat to rely on oil for cooling. Getting the oil into and out of the rocker chambers quickly benefits this cause.
The more full throttle time your engine sees the more critical this becomes.

Posted by: Jake Raby Feb 2 2010, 11:55 AM

.and it is reality, at least in our application where it has been observed very closely.

When Len made some changes to the engine I was skeptical, but the rule is anytime anyone has an idea that parts of our team we go with it, otherwise we'll never learn and will never benefit from our racing..

It worked and it proved me wrong..

Murray, this isn't a 356, if you want to use that mindset I suggest that you work with those engines. Having an open mind adaptable to the ever changing world of engine dynamics is necessary. Close the mind and you may as well just give up, its the same difference.

If my mind hadn't been open with the experimental approach that Len came up with last season we never would have learned what we have about the dynamics of crankcase pressure.

Posted by: Cevan Feb 2 2010, 01:03 PM

I can see why with a vented head, oil in that area would drain back to the crankcase more slowly.

What is the downside to plugging the head vents? The only thing I can think of is there is no controlled excape for excess pressure within the cylinderhead rocker area. But, is this not an issue for a well functioning motor that doesn't see alot of sustained time at high revs?


Now, my L-Jet motor did not have vented heads and didn't leak oil.

Posted by: Jake Raby Feb 2 2010, 01:23 PM

With less head breathing from the valve covers the demand for better crankcase ventilation is elevated...

Posted by: HAM Inc Feb 2 2010, 01:53 PM

The pressure in the crankcase at large is generated in the bottom end, not the heads. The issue with the T4 is that the drain back passages that are just above the lifters in the crankcase are relatively small. If blowby generated crankcase pressure is moving out toward the heads it does so through these small drain passages, making it more difficult for the oil to drain back into the case.

As a side note we experimented with some jaw dropping big vents (over 1.5")on the chimney to see if this would prevent the pressure differential; it did not. Oil still exited the rocker vents.

By eliminating the rocker vents you ensure that the pressure in the bottom end is the same (or there abouts) as the pressure in the rocker chambers, which allows the oil to return to the bottom end without fighting a pressure differential at the point of entry into the case.

The bottom line is that if you have rocker vents the pressure in the crankcase at the drainback point will exceed the pressure in the rocker chambers, thereby inhibiting oil flow back to the bottomend. Period.

The more blowby or full throttle time; the more of an issue this is. Ask yourself why you want your oil to exit the rocker chambers through a hose that then has to run to a vent can and then make its way back to the engine when it could just run back to the case directly through the pushrod tubes.
As Jake said a bit more venting at the chimney is in order, though not a lot more seems to be required. (Brent of Raby Enterprises gets the credit for that observation!)

Posted by: Cevan Feb 2 2010, 01:55 PM

I see that the 1.8 L-Jet motor uses a 22mm hose from the oil filler to the intake tube. That's about 4 times the volume as the 11mm hose D-Jet uses. So I'm guessing that part of the demand for better crankcase ventilation is using a larger hose.

Posted by: ME733 Feb 2 2010, 03:45 PM

............What in the hell...!!!!!("the oil goes through a hose to a breather can and drains back to the crankcase"HAM"). You people must have had a head vent tube kinked, with a down and up loop trapping , and draining oil, through some wierd siphon process. Properly done, and installed , the vent lines from the heads-continiously rise...go up to the catch can, breather box.ANY OIL slung to/into the breather tube will simply drain back to the head.... the hot VAPORS/WATER-IN THE FORM OF STEAM will rise to the catch tank to condense back into what they were...JUST DRAIN... a catch tank and SEE THE WATER, and liquid crud....AND JAKE RABY I was building 914 RACING engines,and 356 RACING ENGINES, and 911 RACING ENGINES, and doing complete turn key race cars........when you were still crapping in your diapers. SO DO NOT tell me what engines to specialize in. I have already gone down the road you are on now, and eventually you will rediscover a very simple yet elusive answer. SO PEOPLE....I still recommend using the STOCK head vents, to the stock location/ filler/location/ routing to the air box, or into the carburators....Unless of course you decide to use a much larger remote catch tank thats well vented. AS we all know the 914 heads are susceptable to cracking, and warping. Anything that can be done to remove heat from them just adds longitivity, and reliability. So VENT the head and help get some of the heat out of them....MURRAY .

Posted by: HAM Inc Feb 2 2010, 05:01 PM

I'm not intersted in argueing with anyone, but when someone implies that I'm stupid enough to make judgements based on observations made on a chassis dyno with kinked breather hoses...I have to respond!

No kinks or wierd process; just good ol' gravity.


Those vapors don't originate from the rocker cavities, they are a by product of blowby. No justification for venting the heads there.


Oh Lord, not another one of those! When someone says something like that it is obvious that they feel they know it all and have nothing left to learn. And I suppose you were also reading and writing when Jake was still pooping in his diapers, but it hasn't kept him from doing a better job with his grammer. There's a reason I quit reading Cormac McCarthy! You reminded me of it.


Okay now you're just being rediculous. If your implication is that venting the rocker chambers will somehow reduce the propensity to cracks and warpage you need to let to go of the crack pipe and and take a closer look at one of these engines!

I spent a lot of time on this subject. Jake and his team at Aircooled Heaven were involved and Jake conducted the tests (that's tests plural, there were many) while I observed the funtion of the various breathing systems we worked with. The results surprised all of us, including me. But the test were done using a scientific method and then the system was put to the test on the track with a season of racing...hard racing. The results were no leaks, no blowby issues, slightly lower oil temps and superb reliability.
If you have a stock FI engine that uses the vents, keep that system intact. It actually draws air into the rocker chambers and pulls oil toward the bottom end.
If you have a carbed engine breath it from the chimney and if you are concerned about the condensation run the hose into a can about an inch or so above the bottom so you can drain the condensation.

I have said all I have to say about this.

Posted by: bandjoey Feb 2 2010, 05:12 PM

Letter from a getting old fart.
Dear Murray: This is a tough one for a non mechanic minded driver like me. I've absorbed every sports car magazine and book I could find for most of my 60 years and have seen a lot of old ways fall when science is brought into the mix. In the 914 'world' Jake and Ham have spent more money on engine science than I anyone. So I have to respect that. The engines at Daytona from 1980 won't take the punishment the 2010 engines do because someone spent a lot of money figuring out a better way. Now, don't hit me with a wrench. You'll always be a better builder in a day than I am in a year.

Thanks for your input.

Posted by: jaxdream Feb 2 2010, 05:15 PM

Ok , Len , I came out of the rootcellar , don't let one guy dampen this thread , like I said earlier , I have some learnin to do , and having vetrans speak up is what I look for. Not all of us have the experience or the surroundings to garner such. Heck there are probaly 2 dozen on this forum that would give their eye teeth for the opportunity for such experiences everyday , but alas not all of us need to be engine builders, still need Dr.s, plumbers, even lawyers and such.
This thread is getting some hard core info put into it, I for one would like to see more of it , even including what others have to say different . There is usually differing points of view to most every facet of these cars and thier engines.
Please sir , more.

Jack / Jaxdream

Posted by: jaxdream Feb 2 2010, 05:18 PM

Mods , don't lock this thread yet ......

Jack / Jaxdream

Posted by: bandjoey Feb 2 2010, 05:21 PM

Ditto's. More.
Vent it from the chimney means a hose from the filler neck to a can?

Posted by: ME733 Feb 2 2010, 06:15 PM

..............I believe that,s the implication....AND. it needs to be REAL BIG ALSO, was it 1.5 inches in diamenter???? If head venting is deleted.....was the mantra. MM

Posted by: Cevan Feb 2 2010, 07:36 PM

I think that's the idea. I think I will use an L-Jet oil filler. As I posted above, it's 4 times the cross-sectional area of an 11mm hose.

Posted by: bandjoey Feb 2 2010, 07:41 PM

Now the run to classifieds...and who will corner the market on Ljet Chimneys first?

Posted by: Jake Raby Feb 2 2010, 08:46 PM

WOW, another one of those guys that have continued to stagnate development with their 35 years of bullshit doing the same thing over and over again with a closed mind.

You'll not get anywhere with me with that mindset or kind of screwed up outlook on the topic at hand.

I've had more engines wasted by people that called me up saying "I've been doing this for 35 years" than anything else.

Until LAST YEAR my outlook on cylinder head breathing was the same as Murray's. That was proven wrong by studies that we did on my engine and chassis dynos as well as an entire season of SCCA competition.

My Employee, Brent who has been with me since day one gets the credit for the hypothesis that the heads had too much breathing capability... EVERYONE else on our team did not agree with him.

I was wrong and I'll admit it... I was open minded enough to do the exploration and pay attention to the results.

Posted by: Jake Raby Feb 2 2010, 08:52 PM

BTW- Murray which Type 4 engines came from the factory with head vents(VW and Porsche combined)??? Being the all-knowing individual you are I'd expect you to have the case codes of the equipped engines and part numbers of the cylinder heads memorized.

I do.

Posted by: johnnie5 Feb 2 2010, 09:19 PM

Posted by: jaxdream Feb 2 2010, 11:24 PM

Ok, Jake and / or Len , would a setup running off of the oil filler housing , enlarged so as to pull a bigger volume of crankcase gases out from the oil filler also need some sort of PCV valve , or just run without a PCV valve. You guys have my attention, some clarification on what exactly you are reccomending would be GR8 !! Thanks for your replies , so far this is an informative thread being that I will be using carbs for induction ( 40 IDFs ).

Jack / Jaxdream

Posted by: Gint Feb 3 2010, 07:37 AM

In fact I couldn't agree more. ME733 is usually a bit... shall we say overzealous is relaying his beliefs. But please don't make the rest of the 914world community pay for that. This is a great thread with some good information being brought to light. I for one would love to see the exchange continue.

Posted by: ME733 Feb 3 2010, 08:47 AM

..........Ok , I shall continue to point out the absurd falacy of UNVENTED HEADS....Some of you people have become so convinced over the postulating of this little selfserving group of mechanics and marketing whizbangers, that I really wonder sometimes how you people got to the place your IN. So as JAKE wants to continue this dialog-with his -all knowing- points of view, I WILL ADD A FEW MORE COMMENTS.............1) I dont need to memorize what(years) heads have or don;t have head vents....I used to just drill-tap- made my own.( like you have previously done and discussed)....2. going down the road of ...the oil drains back faster with unvented heads....I have to wonder EXACTLY AND PRECISLY...how this observation was accomplished..(sort of along the lines of Melling oil pumps have internal oil leaks which you people have stated)...3. And If the oil drains back faster, it,s due to the FACT that the oil is MUCH HOTTER.(and breaking down)..due to the fact the HEAD is much hotter, Due to the "trapped " heat in the head.(with out vents)...4. the trapped heat has many down-sides., not the least of which is...(drum-roll)....the Increased heat affects the VALVE SPRING tension, and that affects how the engines top end, ( cam lobe tracking,)( valve bounce)...at way high RPM,s is affected. Hotter the springs=loss in valve seat pressure.=shorter valve spring effective pressure/life. Ok .(solution)..so just increase installed seat pressure..=...that increases rotational force...just to turn over the engine. (use torque wrench to conferm.). This get you into robbing Horsepower that you busted your ass to create in the first Damn place. Unvented heads have no advantages...street or race....5. Did I read that you people believe oil does not cool the HEADS/ engine? Really? honest ??????.( you probably made a typo error)...6. HEAD VENTING is a good thing in any form....O.E.M. or otherwise.

Posted by: HAM Inc Feb 3 2010, 08:51 AM

A single central vent from the chimney needs to be no larger than a 3/4" heater hose. Where you route it is a subject for discussion. Don't even consider routing it to the exhaust for a crankcase scavenge as that only works at full throttle.
My dad conducted dyno studies on his race T1 engines back in the 70's utilizing exhaust evacutation. The engine had to be totally sealed. It would develop about 3.5-4" of crankcase vacuum and was good for a consistent 1.5% increase in power. But only at full throttle. At part or no throttle there is pressure in the ex system.

If you are hell bent on running head vents limit the I.D. of the barb to 1/4" or less.

Posted by: Jake Raby Feb 3 2010, 09:05 AM

I was expecting a much more dramatic reply from Murray. He ruined my day. Trust me, I was prepared for engagement and still am. (I spent some time on Google last night and had a lot of really good laughs!)

How about two race seasons.. The same engine was used for both seasons. In the first season we had issues with oil control toward the end of each session. I could duplicate this situation on the chassis dyno if I simulated race conditions with throttle and RPM, sometimes seeing 8,000 RPM for 5 minute stints without mercy. The issue would occur at any oil temperature or oil pressure.

In the second season we tried a wild and crazy idea and blocked off the head vents in the heads and the problem could not be replicated on the chassis dyno. We then took the car to the track and didn't have an issue all year long. We had no more than a shot glass full of oil in the catch can all season!

Since this experience I have continued to experiment with this on my personal cars and gather data to support it from other competition and full street engines.

Murray, have you ever purposely blocked off a vented head on a 914 engine to see what occurred?

Posted by: HAM Inc Feb 3 2010, 09:14 AM

You know Murray, for a guy who was building engines when Jake was pooping yellow you sure have a weak grasp of theory.
Oil cools the valve springs, not air. But I will concede that in as much as the heat that the oil draws from the springs and rockers is generated by the heads one could accurately state that the oil does cool the heads. But it's BTU absorbing capacity is not up to the task of drawing a significant amount of heat out of the heads, so it only benefits the springs and rockers. Which brings me back the point about unvented heads running slightly cooler oil temps.

I'm not interested in going down the line point by point by point with you as you clearly have made up your mind.
But I will point out one commonly held misconception that you suffer with yourself, further indicating that your understanding of engine theory is very elementary.

The cam loading at speed is nothing like what it is at assembly. At near redline speeds the load on the cam at max lift (as the lifter goes over the nose of the lobe) may be 5 lb's it may be near 0. At speed the greatest load that the cam sees is when the lobe encounters the stationary valve train and has to get it moving...and in a hurry. This is why higher rev engines want a higher spring rate (not to be confused with seat or open pressures). And it is why turning an engine over with a torque wrench to gain some understanding of the value of different spring rates AND pressures is useless.
I pass this forward not to educate you (you already know it all) but to inform the community at large who have a real interest in these things and because they are not experts like you are willing to learn.
I have not stepped in in the past when you have made post' that spread misinformation, it's just not my style, but on this subject you have attacked my credibility and the findings of an exhaustive study done by professionals. And I will point out to you that I have nothing to gain if people vent or don't vent their heads. I'm not selling breather systems.

Folks be very wary of taking advise from this guy.

Posted by: type11969 Feb 3 2010, 09:24 AM

Murray ? ? ? ? what would Jake and Len have to gain by ! ! ! advocating for a number of years , , , to # # # use head vents then now to begin advocating not using ^ ^ ^ them? They % % % will @ @ @ not be making any money off of ( ( ( sharing this information. Obviously he is simply & & & sharing his findings . . . for the good of the community. If you doubt his results , , , that is fair but ) ) ) I suggest you prepare logged data showing a sound & & & experimental method because I know Jake and Len _ _ _ have that info.


. . . . . . . . . . Chris . . . . . . .

Posted by: type11969 Feb 3 2010, 09:27 AM

Len beat me to it, putting in all that extraneous punctuation is time consuming.

Posted by: Jake Raby Feb 3 2010, 09:31 AM

Awesome reply Chris... I love the style!

Murray for Mayor!

Posted by: type11969 Feb 3 2010, 09:34 AM

..... thanks ......

Posted by: ME733 Feb 3 2010, 09:51 AM

.....................Yes be wary of taking advice from people who avoid answering "exactly and precisly how you observed ...." and degenerate into a panicky state of personal generalities to avoid answering the stated facts....AND if you can be believed apparently a compressed valve spring has 5-to 0 ft lbs of torque at full compressed height.(valve fully open)(on the nose of the cam).... surely this too was a typo error...(seems like you guys are just digging your hole deeper). who knowes maybe you enjoy self induced flagulation.....Murray..

Posted by: Jake Raby Feb 3 2010, 11:01 AM

You know...
Last night after Murray made his comment about my experience level and age I decided I'd do a little more research about his past in the Porsche world. I just knew that someone with 35 years of experience building super high quality, RACING 356, 914 and 911 engines would have a rich history. I thought maybe I'd read something about the guy that impressed me enough to just let his statements go, because perhaps he was just that damned good.

So I went to the 356 Registry and did some searching... I didn't find anything. I thought that was kinda weird, because all the old timers hang there and SURELY Murray had to have built thousands of engines for that crowd over the past 35 years..

Totally disappointed I then used this little search engine called Google.. The word on the street is this thing is the best thing since sliced bread for finding out about people, places and things here on this new fangled computer "thing a ma jig". So I typed in Murray Mcafee into Google and I didn't find anything at all online related to his experiences with Porsches or their engines... Since I have been known to make so many typographical errors (in the world according to Murray) I thought that just maybe I didn't spell his name right so I double checked. It was spelled right so I then started doing searches with all sorts of other combinations like "Murray Mcafee+Porsche" and that still didn't do anything..

I kept getting pissed off because it seemed that every search I did was polluted with all sorts of information and rants about some guy with the same name that ran for Mayor of his city in 2007; that was the only information that did pop up and finally I read something I couldn't believe. It seemed that the Mcafee character that everyone was bitching about had been the city manager in that city and held other jobs in the past and it was so entertaining that I just kept reading it and laughing my ass off at the wild statements of this guy's behavior in public and during city functions....

As I read more I started thinking to myself that this behavior sure did parallel my experiences with Murray in the past and also was in line with his ramblings here on the forum, especially in this topic. I started to think that maybe this guy was the same Murray here in the thread, but how the hell could a guy that had been tied up with city politics have the time to build so many engines and supposedly win so many races, it just didn't all add up. As I continued to read I'll be damned if it wasn't true!!! He really is that damn good! A phone call this morning verified that here on 914 World we are in the presence of a VERY infamous person!

So I'll share a link or two here and some of my favorite excerpts from last nights google searching so all of you can laugh just as hard as I did.
http://www.thecitizen.com/~citizen0/node/21840

DAMN!


Here is my favorite!!
One Small Step for Senoia... One Giant Defeat for McAfee!!



Another..



Every Village Needs an Idiot



So it appears that Murray was busy managing a city when I was still shitting in my diapers more than he was producing these awesome engines that he carries on about so often here on this forum. He has gone out of his way to ruin my credibility so I felt the need to reciprocate and share a few things that were nothing more than a matter of a simple google search, and total public record.

Did someone mention self induced flagulation (SP)????? LOL

Posted by: Rand Feb 3 2010, 11:02 AM

Murray, put your money where your mouth is. Build a TIV motor that kicks one of Jake's motors' ass. Maybe you could start by matching the results of his cross-country trip. Document it as well as Jake did and let's see it. Good luck.

What kind of performance specs have you achieved out of your best TIV build, and how long did it last under abusive conditions?

Posted by: HAM Inc Feb 3 2010, 12:13 PM

Good work Jake! But I can't but help wonder. Can you be more specific about the sort of computor you used. How can we be sure that Google didn't just make up these results. They surely have an agenda, everyone else does!

I have to admit that I have been sucked into this goofy discussion now and as a result I have to respond to Murray's assertion that cam loading doesn't change with speed.

Here's what I said:

Here's Murray's response:


You missed the point Murray. Ofcourse I know that springs are displacement sensitive. Meaning a spring with a rate of 250lbs/inch will require 125lbs to compress it a .5". What varies with engine speed is waht is actually compressing the spring.

Let's consider an engine that is properly sprung to control the valves at 7000RPM's. When the engine is turning 7000rpm's the greatest load on the cam (notice I said the greatest load on the CAM) occurs when the lobe comes around and encounters the stationary valve train, which it has to get moving in a big hurry. Once the mass is moving inertia plays an increasing role over the course of the lift event. The more inertia the less the cam load.
Eventually as the mass approaches peak lift the load on the cam may be reduced to only a few pound. This is why we can draw no meaningful valve train information from turning an engine over with a torque wrench.
Other factors include the stiffness of the pushrod. If the pushrod is not stiff enough it will bow when the lobe comes around and encounters the stationary valve train. This bowing delays the opening of the valve and stores energy in the pushrod, to be released later in the lift cycle. As inertia takes over and the load transferred through the pushrod to the cam decrreases the pushrod unloads its energy and actually pole vaults the valve contributing to valve float. Did you catch all of that, Mayor?

Now, here's a question that hasn't been broached at all yet in this discussion that could be fun and interesting to the community. Why do we need to vent the crankcase at all, and why do some configurations require more venting than others?. The answer varies by application and engine specifications and is a lot more complex than it appears on the surface.
Mayor perhaps you would like to weigh in on this.

Posted by: wayne1234 Feb 3 2010, 02:33 PM

Wow, I just wanted to clean up my engine bay, Jake has helped me in the past, with nothing to gain on his part, because the part was previously purchased by the PO.. So I feel he is looking out for the good of our community, I'm sure he doesnt have to post on here for his business. If people like Jake didn't keep pushing for more , and questioning what is "written in stone" we would all be stuck with nothing new since the 80's. I'm sure he puts so much into R&D that it would make our head spin... I for 1 am glad to have him here lending us a hand... Thanks Jake

Posted by: Jake Raby Feb 3 2010, 02:37 PM

Thats right. If automotive technology didn't evolve over time we'd still be working with flat heads, steam and the like.

If everyone had their head up their ass like Murray does we'd not have 4 cam, 4 valve engines running 12:1 on pump gas for daily drivers.

Hell I realized I was limiting my exposure to modern day technology by only working on the Type 4, so a few years ago we jumped into the M96 Porsche engine and have learned tons about modern theory and application.

Due to that our vintage engines have benefited.

Posted by: ME733 Feb 3 2010, 03:52 PM

...Well jake arn't you special. Just like the jerk who wrote those UNSIGNED letters to the editor...Only thing is I actually know who he/they are....And because he could NOT meet the zoning, health, building code , access, lot size, ordinance requirements...to convert a GARAGE into an apartment... which I would NOT approve , and my decision was supported by a city council VOTE. this is the extent some "types" of people will go to- when they cannot get their way. I stood firmly for the law, ordinances, and for what was in the public intrest, and the city. now this leads me into the area that YOU MUST believe everything you read. especially considering, you didn't care, or notice the "articles" were UNSIGNED/REAL NAME. I guess you believe unsigned/ arthored automitive articles also. Maybe some of your "theories' come from the same unsigned sources.( completely full of c---.)...But anthing to divert attention AWAY from the points I have raised in this "case venting" discussion. Youre doing this because you are conserned that another engine builder disagrees with you, in public, up front, among the 914 owners, and YOU CANNOT comprend that you do not know everything, and it scares the hell out of you that someone(finally) has called you on the carpet to address a few simple engine breathing points. Again this is why you, are getting off the subject. I think the members are smart enough to realize the obvious....So heres are some facts, find a 1996 guide to vintage racing.(the front cover says/showes it all).the june, 1987. victory lane-pg,s 8,(guest editoral) and 53, (ad)...Victory lane , july 1988-pg-86, car collector Dec-1985, article time travelers go west pg,s 54-thru-57. Walter Mitty Challenge1985,(August-22-25), pg,4,5,7,(pg7...note driver) I built their engine/and helped with some other stuff,.VW Porsche Magizine.., October-1983, pgs 43-43....well that should be enough to get you started. After you do your homework, how about getting BACK to the subject matter ,and questions I raised, and issues related to "head venting" or not.

Posted by: McMark Feb 3 2010, 04:18 PM

If you care to continue the debate, take it into PMs cause nobody else cares.

Posted by: HAM Inc Feb 3 2010, 04:25 PM

Great call McMark.

Posted by: ME733 Feb 3 2010, 04:28 PM

......................If what you say is TRUE, why is it that the Nose of the cam , especially those "flat ones" some people have had ,are worn down radically.at the nose, Instead of at the beginning of the "ramp" near the base circle? as you state., where the highest loading is supposed to be ? did you catch all that?

Posted by: Jake Raby Feb 3 2010, 04:47 PM

McMark is right. Murray, if you want to keep arguing just come to my forum. There is already a thread started there on this topic and everyone there already knows you.

Posted by: SirAndy Feb 3 2010, 04:48 PM

What did i miss?

Posted by: HAM Inc Feb 3 2010, 05:58 PM

Nothing go back to sleep!

Posted by: Twystd1 Feb 3 2010, 06:10 PM

This is a great thread.
I am learning a lot about venting. Oil and otherwise.

Keep it up fellas. Cause they don't teach this stuff in any Type IV book.

And the humor aspect is superb.

Thanks and keep it coming...!!!!!!!

Clayton

Posted by: ME733 Feb 3 2010, 06:33 PM

..........Well the only thing you missed was ... any direct response, or answers to SPECIFIC Questions asked of the" raby gang". I mean any question, alternatate opinion, or discussion which is not originated by the gang, must of course be a "personal attack on my business". Look back over the course of this "discussion". note all the points, questions, that were not answered, and avoided....Now the really absurd aspect of all this is,; I actually like what jake has done, and is doing. ..But when IT,s impossable to enguage in a spirited debate, discussion, or have questions answered directly, then , well , what the hell, just thought the discussion could be of value to 914 owners who can think for themselves and appreciate options to problems....signing off ...Murray.

Posted by: ME733 Feb 3 2010, 06:38 PM

.........terrific, when I was much younger I loved a good bar fight., that was back in the days of vietnam, USN., ....see ya soon., jarhead,....Murray.

Posted by: Jake Raby Feb 3 2010, 08:01 PM

We'll save you a seat...

Posted by: r_towle Feb 3 2010, 08:28 PM

Some people built racing motors before the Internet.
I dont know Murray, but based upon his age and the many magazine articles that I cant read (I dont have the magazines) I suspect that he did build a few motors.

The 356 registry is not populated with all the 356 guys...many of them avoid forums for this exact reason. Many of the top 356 engine builders never visit these forums and its not because they are scared, its because they dont like all the drama. Its also a time suck they would rather avoid.

I have met quite a few, and many of these guys do know what they are doing and have built some really cool motors and hotrod stuff.

On the head venting question, I have a few that have always puzzled me and hopefully one of you guys may have a theory....we have discussed this before with no answer.

So, Early Djet has head vents.
Later Djet does not have head vents, but has air injection
Ljet has no head vents.

Does anyone have a theory why the factory kept flip flopping on this specific issue? I know racing was not on the line here, but was is longevity?

Rich

Posted by: 904svo Feb 3 2010, 09:06 PM

They had to meet the EPA requirements on Hyro carbons for emissions, this was
the only way they knew. (bookkeepers way)

Posted by: pbanders Feb 3 2010, 10:03 PM

Remember that this was very early in the day of tighter emissions control and the advent of various types of FI systems. Some of these changes may have had to do with apparently unrelated issues (e.g. idle stability). Unless we've got a direct line to the engineers who made the changes, I suspect the exact reasons are lost.

These cars were an amazing advancement in terms of emissions over the previous generation. Crankcase scavenging, evaporative fuel systems, tight mixture control over a wide engine speed and manifold vacuum range, etc. And to make it worse, they were all open-loop!

I'm continuously amazed by where this has led us to today. Modern engine designs with engine management systems do an incredible job of managing all operating conditions while maintaining low emissions, good fuel economy, and drivability.

Posted by: jaxdream Feb 3 2010, 11:55 PM

Jack / jaxdream

Posted by: luvatenor Feb 4 2010, 05:03 AM

Hi- I have a single Weber conversion. Where would i vent from the oil filler breather box?- Do I have to buy or construct a vent box(wrong term)? Gees, I didn't realize the discussions would get this heated. I benefit from everyone's input because of the expertise and experience which I do not have- Thanks again

Posted by: McMark Feb 4 2010, 05:28 PM

The vents on the oil filler and the heads (if applicable) should be vented to the intake or vented to atmosphere. They should never be connected together in a closed system (i.e. it's improper to connect the filler to the head using a tee and three pieces of hose).

To say it another way, all of the engine vents should be 'open'.

Posted by: ConeDodger Feb 4 2010, 05:51 PM

Wow. I guess we have figured out how to get a lot of information out of Jake and Len. Just piss 'em off

Posted by: HAM Inc Feb 5 2010, 10:37 AM

Who's pissed? I have nothing but love for everyoneLOL!

Posted by: ConeDodger Feb 5 2010, 10:45 AM

Listen HAM-head (Also known as Head of HAM) if you are still repairing my LE200's block off my head vents.

Posted by: ME733 Feb 5 2010, 11:16 AM

............Good grief.....the number of brainwashed , lemmings, is higher than I had supposed....of course it,s always easier to be a brain dead follower, than to have to take the time to think for yourself.....I still highly recommend using HEAD VENTS on your 914 engine. For many reasons.......Murray Mcafee.

Posted by: rtalich Feb 5 2010, 11:50 AM

Oh give it a rest already! As entertaining as this thread has become, its also getting old. Your personal, unproven opinion, which is exactly what it is, with no scientific facts to back it up, does NOT out weigh good 'ol realistic solid data. Which, BTW, Jake and crew has gobs and gobs of. Go back and do what you do best... run for Mayor or some other public office... wait a minute... that didn't work out so well either I don't know... maybe you should be a politician. You'd probably fit in better in that crowd

Lets put it to a vote... who'd you rather have build you a Type IV motor? Murray, who's knowledge about these motors appears to be stuck in the past? Referring to the magazine articles he posted a few posts ago... 1980's???? Give me a break... A LOT has happened from then till now, thanks to Aircooled Technology.

Or Jake, who's knowledge of aircooled motors are second to none! With tons of R & D AND DATA to back it up!!

Posted by: HAM Inc Feb 5 2010, 12:16 PM

Rob your heads will be front and center here shortly. All you need to block off the vents are 1/4npt plugs.

Posted by: ME733 Feb 5 2010, 12:29 PM

................I didn't post any articles....Just advertisements....The articles were written by reporters,with a real names, for the particular magizines I listed. Murray Mcafee.

Posted by: jcd914 Feb 5 2010, 07:46 PM

I personally won't do away with my head vents.

I understand why Jake, Len and others would want to insure the oil return fast to the crankcase but I don't see where the average 914 engine is going to suffer from the oil build up that their racing engine has. A true racing engine is a different animal than anything most of us have, nor would we want one the way most of us drive our cars. I don't recall seeing how much the oil temperature was raise and I did not understand what Jake meant by "oil control issue" but in a racing engine you need to do what ever you can to control temperatures and insure you are not sucking air instead of oil.

I am going to retain the stock PCV (Positive Crankcase Ventilation) system as originally installed. The concept of a flow thru PCV system is to get all the fumes and moisture out of the whole engine. There will be some moisture, vapors and such that are released from the hot oil in the heads and should be vented. And if in the future I move away from the stock FI and go to carbs I will not be venting mine to the atmosphere but routing into the intake to be burned by the engine. It is not as easy on a carb'd engine but it can be done.

IMHO Use the stock system for a stock engine and for most mildly modified engines. Do not use a road draft tube or and if you can't bring your self to route the fume back to the engine to be burned at least use a catch tank or vent box the contains the mess.

Jim

Posted by: HAM Inc Feb 6 2010, 11:56 AM

Engines still running the O.E. F.I with vented heads should definitly maintain the original vent system. IIRC it is a draw through system, meaning air is drawn into the heads and down the pushrod tubes.


The oil temp difference was ~10*. And by oil control issue what Jake was referring to was the observations we made in our test' of various venting ideas.

We found that more oil wound up in our catch can when the heads were vented than when they weren't. And we also found that the more head venting area we tried the more oil ended up in the catch can. The test' conducted were always of a full throttle run (on Jakes chassis dyno) of ~ the same duration. We then simulated race conditions (to some degree) by running at full throttle then half throttle then back to full throttle. The results were the same.
When we completely did away with the valve cover vents the amount of oil in the catch can almost completely went away.

The lessons were very clear. The oil will take any path out of the rocker chambers available to it.

When the rocker chambers are vented it has the effect of creating three seperate pressure chambers, with the central crankcase area having the greatest pressure as it is the gathering point for blow by and the very strong pulses generated by the movement of the pistons. Because the pressure is greatest in the crankcase, and because the drain back slots in the case are relatively small, the returning oil must overcome this differential with gravity only. Remember that the oil being pumped into the rocker chambers is done so under pressure, while the returning oil in a vented rocker chamber has only gravity to work with. Take a look at the incline of the pushrod tubes. They are pretty level.

As I said earlier in this thread by eliminating the rocker vents we turn three seperate pressure chambers into one which eliminates any pressure inhibitions to oil returning to the crakcase. And since the oil being pumped into the rocker chambers is done under pressure from the oil pump, by sealing the rocker vents that oil pressure can actually help evacuate the rocker chambers. I should also point out that if the pressure in the rocker chambers is allowed to drop to atmospheric, valve guide oiling is reduced as well.

It also bears pointing out that the vapors that are generated and circulated in the crankcase are the result of blowby and windage and have little to do with the rocker chambers.

It doesn't matter to me if folks want to vent their heads or not. It blows my mind that the whole debate has gotten so heated at times. I just thought I'd share the results we came up with in a serious study of the issue. Our 8,000RPM race engine has a single -12 (3/4") vent coming from the top of the chimney and that is all. No oil leaks or oil consumption.

Posted by: Gint Feb 6 2010, 12:54 PM

If the heads weren't vented, where would the catch can get any oil from? In other words what was/were the input to the catch can besides the head vents? Or is the answer to that question what you said in the next quoted text:

I appreciate you taking the time to pass along your observations.

Let me see if what I now have in my mind is correct. You're saying that if the heads are vented, oil will find it's way out of the vents regardless and that the force of gravity for the oil to return to the heads and subsequently the crankcase can't overcome the force of the crankcase pressure pushing the oil out of the head vents in the first place. Yes?

Posted by: HAM Inc Feb 6 2010, 02:21 PM

We tested with both the the chimney and head vents, then we tested with just the head vents and we tested with just the chimney vent. Lots of oil came out of the heads. Very little came out of the chimney.

That was our observation.
It is my opinion that if the return area below the pushrod tubes in the case were nice and large like a T1 this wouldn't be an issue. Because they are narrow slots in the T4 the pressure pushing through them towards the vented heads overpowers the oil trying to drain. Think of it as a wall of pressure at that critical point.

Posted by: Gint Feb 6 2010, 02:57 PM

Thanks!

Posted by: yeahmag Feb 6 2010, 02:58 PM

Are you venting from the only from the oil filter/baffle at the top of the engine? I've all ready disabled and opened up my PCV, but would like to try this modification on my carbed engine...

Any pictures?

Thanks!

Posted by: ConeDodger Feb 6 2010, 03:03 PM

Len,

You say you had a >10 degree difference in oil temperature. I assume you mean your oil was cooler? Did you see any change in CHT between your test configurations?

Jim brings up a good point. If your engine is stock it should remain as designed. Mine is not. When finished, (soon) it will be just under 2.4 liter TypeIV with Jenvey throttle bodies and SDS injection with crank fired ignition.

Posted by: 7275914911 May 3 2010, 09:03 PM

Don't mean to open any old sores here but....

Here's what I am trying with CFR Breather Can after reading this thread and the thread at Jakes site. My heads were not vented and I was going to vent the VC's(lazy way) and butcher the tin.
Instead I have modified the Filler a little more by adding an extra vent in the base of filler. I will keep 1 opening of the can plugged.
I had noticed cooler oil temps since installing CFR breather with just the filler vent and flow back installed. I was using a 1.8 filler straight to BP oil bottle with KN on top. Bottle filled up quickly and was a little messy. CFR breather keeps the mess contained in the case.


Thoughts??
Ken

Posted by: HAM Inc May 4 2010, 08:01 AM

.

That's plenty of breathing capacity for a healthy street engine.


No.

Posted by: ME733 May 4 2010, 08:48 AM

...................Well HAM...It seem like you are one of the ones "folks should be leery about"....here,s why....1.you FINALLY concede that oil cools the valve springs.2. fuck you, requarding you opinion of my "elementary" knowledge.3. how long you been building racing engines?, and customer engines that WIN PLACE OR SHOW at National level races.???, anyone who knows anything about SCCA racing, knows that regional racing is for begginers....so what.... you "beat" a few begginers in racing, in the lowest level of racing....I, aint impressed. when you know it alls qualify 4-5th on the qrid at the SCCA NATIONAL RUNOFFS for at least SIX YEARS in a row I might give you a little respect....when you have 12 customer cars-that finish 1-12 at a race...maybe I,ll give you some respect....so far all you seem to be is a smart ass, think you know it all....(with a conceded attitude)....BUT LETS GET SPECIFIC about "cam loading"and the necessity of keeping the valve springs cool, by virtue of oil temperature control, with vented heads, assisting....SPECIFICALLY. WHAT IS THE CAUSE OF....the flat cam problem....this occurs at the "NOSE of the cam, NOT, NOT, NOT at the camshafts ramp.".your ..quote''is ...the highest loading is when the cam has to get things moving".....this is simply NOT TRUE.....That is why a properly made cam has a big radus base circle, and gentle ramps to EASE the lifter,pushrod,rockerarm, into action....The highest loading IS on/ at the NOSE of the cam......thats why it wears down, even in a perfect assembly...very slightly....so if you are right .....why is the "nose " wearing off...instead of the base circle, acceleration ramp???....it,s because your wrong in terms of where the highes point of loading occurs....5 you say rotating the engine over to assess valve springs is USELESS....this is because you have a valve spring compressor and believe it,s the only tool necessary for this analysis...and you like shortcuts, and must have your "theory Book"right beside you............................Now just so you know...I owned a engine dyno for some twenty years.and used it extensively, yep even on type IV engines....what.... you guys are into your 2nd or third year?.I aint impressed.your want me to get into how you bump up your H.P. numbers?..just keep making your shitty comments......OTHERWISE. just address the CAM LOADING question, and facts .................................your buddy, murray.

Posted by: Jake Raby May 4 2010, 09:06 AM

WOW! Talk about an awesome display of tact and professionalism.

Posted by: Rav914 May 4 2010, 09:26 AM

This just infuriates me. Completely uncalled for. I don't care what your gripe is, comments like this degarde the civility and clout of this board. You got a problem, call the man on the phone.

If it were up to me you'd be banned this instant. This is/was a very informative thread. Keep it out of the gutter.

Posted by: ME733 May 4 2010, 09:32 AM

...............hello jake...........I attempted to join in on your website...AS YOU... invited me to do so....., however I decided that ALL THE PERSONAL INFORMATION you require , including an existing member REFERENCE is just a level of your parinoid bullshit I wont deal with. Clearly this is your way to C O N T R O L the members, their comments, and opinions...you have a problem with honesty.you might make a 2-3-rd class dictator......and I never claimed to have ANY TACT whatsoever especially with lieing bastards with conceded attitudes....in any walk of life... I know it,s a fault, but I,m an old dog.

Posted by: Vacca Rabite May 4 2010, 09:44 AM

What? WHAT?! I was totally looking forward to a classic Raby chew out here. Come on, he put it right over the plate, and you bunted!

Seriously though. Murrays comment was uncalled for. You are a drain on our forum sometimes, and just seriously insulted one of the members here that has dedicated himself to producing quality new parts for our cars - helping to keep us on the road.

Admins, can't we get a ban for this guy already and be done with it?

Zach

Posted by: HAM Inc May 4 2010, 09:48 AM

I have very little time to address the lunatic ramblings of a pile of . To busy making torque for engines with no head breathers!

Mr. Mayor you may have bolted together some engines over the years that performed well, but hey, even a blind squirell finds a nut once in a while!

I won't waste much time on your cam loading nonsense, but as for the nose wear, think about what I said.

How much time (expressed in % of run time)do you suppose an engine spends at redline or near redline speed? Not much on a typical course. As speeds slow from redline, loading on the nose increases, as does wear. This is not evidence of the non-existence of cam load shift that varies with speed. In other words where the max load occurs on the lobe varies with speed.
Think about it dumbass. Then watch a spin-tron in action. Then spend hours on the phone with valve train specialist. Maybe your knowledge base will catch up to ours, though I doubt it as you are to stubborn to allow facts to interfere with your accepted ideas.
BTW, considering how much time I spend reading, talking with valve train specialist with whom I have been doing business for years and on R&D and track testing I think it is very unlikely that I deserve the know-it-all tag. That is generally reserved for people who do no R&D and whose knowledge base has not expanded in over 30 years.

Please feel free to go yourself!

Posted by: ME733 May 4 2010, 10:03 AM

.................ZACK........why don't you read the "GANGS" comments transposing youself into my shoes.... I have put up with plenty of nasty, crummy comments,selfserving,arrogent, comments from these jerks long enough....and they AVOID answering questions, and , with people like you chiming in distracting the question line...just playes into their hands...so ZACK just shut up., unless of course you are one of their toddys., in which case you can"t.

Posted by: J P Stein May 4 2010, 10:12 AM

Give em' hell, Muarry.

How bout a new rule: Anybody that critizes Jake & company gets an automatic ban. That would fit nicely with the mentality on this list.

FYI, many racers back in the 70s & 80s ran T-4 quite successfully....and *had the results to prove it*.......they always had an extra engine or 2 in the trailer....
You wanna rewrite history to include your present heros, feel free.

Posted by: charliew May 4 2010, 10:46 AM

This has been a pretty good thread, I wasn't aware of the small return passages of the t4. Except for the on going comments from one who thinks he knows it all about old technology, these were thoughts from the 60's. I like to learn about new theorys. One of the first places I learned about the new oils was from Jakes discussion about the flat cams, I actually found it searching for the changes to new motor oils, it made sense about the oils being changed to keep the cats and o2 sensors working to remove all the good friction stuff as roller cams were now being used. Ok all I want to contribute to this is a little of what I know from trying to do breathers on all my past modified motors. NONE of which were race motors. In the late 70's I started trying to get pcv stuff to work as I was tired of the moisture buildup in the motors. I have found out many years later it was from trying to keep the oil too cool mostly. One motor had larger than stock ring gaps and forged pistons and was spinning 8k a little each day usually for only short intervals. I was also trying to run 10:1 compression on premium gas during the summer with 100 degree days. This required water injection. I used a 160 degree thermostat. All of these things were helping to put water and blowby in the motor. The forged pistons were loose, the ring gaps were bigger than stock and it took a longer time to warm up. The warm up is the thing, the quicker the oil gets to 200f the better for the motor. I learned some of this working with the flat 4 suby turbo motors. The turbo suby always uses oil, especially the loose built motors. The suby uses a oil heater/cooler. The suby has bigger return passages than the t4 but it also has a valve cover balance tube between the heads along with the pcv system. We have also added a port in front of the turbo with a one way valve (another pcv turned around) to give a lower pressure path under boost to try to eliminate the crankcase pressure of the loosely built turbo motor under boost. We also use a Mann Provent from a diesel application that drains to the pan. We got the idea (my son has the hotrod suby, he is also a me) from the Ligenfielder turbo corvettes. I do believe race built motors need a entirely different breather system. You call a race breather system a oil control system. The race oil doesn't stay in for months in the motor. The street car gets idled a lot and doesn't ususlly get the care in the oil area that a race motor does. I live in the country in TX where cow farts probably cause more problems than my 6k miles a year causes so emissions is just a by product of my breather systems. I want whats best for the oil and the motor, to keep it from breaking down and getting contaminated and to keep it in the motor as much as can be achieved for 3k miles. Thanks to Jake and Ham for the shared knowledge here.

I forgot about this: several years ago I tried to make a 1200 sportster keep up with my v65 v4 1100 honda. The honda was 130hp stock the sporster was about maybe 60hp stock. About $4000.00 dollars later with everything we could come up with including coatings and redesigned hemi design heads, roller rockers and all. A big improvement came from a bigger scavengeing oil pump to get the oil out the case and maybe pull a vaccum on the rings and get the oil out of the rocker boxes and a crank vent on the rocker boxes. I could actually feel the high rpm difference. It also stopped the excess oil from coming out the breather line into the air breather and leaking down all over the side of the bike when you put it on the kick stand. This would happen every time it spent any time at 5k or more. Well the hd only made 95 hp at the wheel but it did still sound like a hd and had a good idle at about 1k. I guess this is kinda like comparing the four valve suby or honda to the t4 or t1 though so it's really not a fair comparison.

Posted by: Jake Raby May 4 2010, 11:19 AM

Yet again you are incorrect. The "reference" is NOT REQUIRED, and it is built in to the forum software as a way to give existing members a pat on the back for recruiting new members. Had you left the reference field blank, you would have still been allowed to gain entry.



Damn right it is, because I own the site where I post critical information. I consider entry into that site just as critical as entering the gate to my facility, which is also a controlled environment that you will never see.

I started that forum to share information in a controlled setting so I could keep trolls and pirates from stealing our ideas and copying and pasting them on their own sites, like happened to us in 2004. So yes, it is a controlled environment for those who have an OPEN MIND to both share and learn.

.
and you have a problem with perception and are somewhat paranoid.


Probably a good first class dictator, because in this business that bears my name and on top of this hill what I say goes. If someone doesn't like that they don't have to pay the price of admission. I am not conceited, I just say exactly what I feel and don't take smart assed statements from anyone, and I don't care if you like that or not.


Now you are making statements that we have falsified statements and data..Nothing like some false accusations to help build your credibility.

.
We noticed.

Glad to see you lacked the mental capacity to properly complete your registration onto my forum- it saved me the effort of having to eject you.

Sure seems like you are filling the role that the "lying newspaper reporter" explained in his article about your ramblings and antics.. Sure that guy was a liar?


I'll close by stating that I have been working to quantify what we have learned on the track from the FP 914 engine in our street cars. So far the data I have gathered seems to be absolutely in line with the findings that we have experienced on the track. When I collect an amount of data that can shut down even the best argument I'll be sure to post that over on my forum where we can chat about the Mayor and his ramblings and have a good laugh.

Nothing ever stays the same. Closing the mind because one feels they have been there and done that since the sixties is the fastest way to beat yourself. Had our minds stayed closed and we let our theory and experience get in the way we'd still be having issues that were solved by some experimentation.
What hasn't changed since the 60s in this world?? (other than Murray's mind)

Posted by: SirAndy May 4 2010, 12:00 PM

From my (limited) experience, the head vents have negative pressure (suck in air) at low rpm and have positive pressure (blow out air) at higher rpm.

That would explain why you see that much oil pushed out of the heads at constant high rpms on your race engines.

On a street engine, that oil will have a chance to be sucked back into the heads during lower rpm phases.

On my (street) 2056, i observed oil being pushed into the catch can during higher rpms and then drain back when the rpms dropped.
My catch can was designed to allow for the oil to flow back into the system.

Andy

Posted by: Jake Raby May 4 2010, 12:08 PM

Except during periods of sustained RPM and speed. Thats where I have noticed the biggest differences.

I recently had an AX customer who was having low oil pressure issues on some longer courses. I told him to try blocking off the head vents to see what the results were, he emailed me back to say the issue disappeared.

He had the issue on the street a couple of times on the way to the track on a certain freeway off ramp after maintaining constant speed and RPM for 20 miles on the way to the track. He said this issue also disappeared. He has since blocked off the vents permanently and I recommended him to increase the size of the crankcase vent.

No one needs to take any of these statements as gospel.. Every application is different along with every set of components and there is no "one size fits all".. Just try it both ways and see what happens to your vehicle/ engine.

Posted by: bandjoey May 4 2010, 12:20 PM

Soooooo. If someone with a math background will be kind enough to add up all of the yesses and noooo's to head vents, divide by the number of curse words, and calculate the winner.....

Posted by: vsg914 May 4 2010, 02:16 PM

So, I'm at the final stages of building a 2056 on a 76 case. Two hrs ago I purchased two barbed fittings to drill and tap the bosses. Then I saw this thread and just read all 7 pages. WOW! This engine is using the D-jet. If I read you right Len, go ahead and drill? The air inject sys was removed years ago and holes plugged. The owner has complained to me for years about the high oil temps. Is the unvented heads the reason for this? Will venting them cool the temps.

BTW Great thread (except for the profane gesture).

Posted by: John Jentz May 4 2010, 02:27 PM

Remember, the L-jet 1.8 and '75-'76 D-jet 2.0's did not use head vents and mine does not fill my air cleaner with oil. I'm going to put plugs in the holes I asked Len to put in my new heads.

Posted by: J P Stein May 4 2010, 02:37 PM

Can you boast a record greater than this:

Wayne Baker's Racing History

(Just the relevant parts)

In 1974 we started in PCA time Trials campaigning a 914-4 Porsche. We also prepared customer cars for Time Trials and SCCA Racing.

In 1975 with a 914-4 2.5 liter we won the PCA Zone 8 Unlimited Class.

In 1977 we entered SCCA Regional and National events running a 2.0 liter 914-4 Porsche in D-Production.

1978 we won the D-Production Southern Pacific Championship.
We progressed to IMSA Road Racing series campaigning a 914-4 in the IMSA GTU class under 2.5 liter engine.

In 1980 we finished 6th in class at the 24hrs of Daytona and 12th in class at the 12hrs of Sebring. This was accomplished with a 2.0 liter 4 cylinder push rod engine.

In 1981 we campaigned a 1,680 lb. 914 Porsche with a four cylinder. 2.1 liter engine in the IMSA GTU Championship finishing 4th. Our best result that year was a 1st at Sears Point, this was the first and only time a 914-4 push rod motor had ever won a major race of that caliber.

Posted by: Jake Raby May 4 2010, 03:14 PM

Mr. Baker's accomplishments are outstanding. No one can ever take that away from him.

BUT then the cars were newer and the competition wasn't primarily using OHC and fuel injection like we face today in SCCA F Production with most all other competitors..

Like I said nothing ever stays the same, including the competition...

Hell I thought JP would never sell his 914, proof that nothing ever stays the same..

BUT that has nothing to do with case and head ventilation.

Posted by: ME733 May 4 2010, 04:51 PM

.......................VERY COOL.......JP I was at (that race!!!)..the 12 hrs of sebring.....met you guys briefly....It was a very incredable feat that the little four cylinder performed., so well and finished at all., much less 12th, given the competition....you didn't notice probably, but I gave your car a close lookover after the race., I was absolutely astounded at the road crud, tire bits, oil, dirt, rocks,and chipped paint. the little car went thru hell, and survived!!!!..It took knowledgeable drivers to get the best out of it , while not abusing it to death.......very ,very cool.......

Posted by: J P Stein May 4 2010, 05:28 PM

Murray: That was a quote from his website......I'm not part of "we".

Jake: a lot of pushrod motors above you on the runoff charts. The Kirby 914 won in 06....but then, that wasn't one of your motors.

Posted by: Jake Raby May 4 2010, 05:36 PM

Actually the Kirby 914 won in 05 and Len and I were there..

Then shortly thereafter Dave finch stated that no other 914 would be competitive in FP due to the rules and the competition of today.. In fact he stated that in the Excellence article about that car.
That didn't stop Len andI from building one.

Yet again, this doesn't have anything to do with case venting.

Murray had you confused with Wayne Baker... Now thats funny... looks like someone is "baked" themselves.

Posted by: J P Stein May 4 2010, 08:51 PM

Right, 05......

I dunno much about T-4s, but I have seen pics of T-4 valve covers filling with oil at continuous elevated rpms (IIRC). Venting the valve covers would seem iffy without using some method to keep the oil level therein down and in the case/oiling system where it belongs.

"They" had (in the old days) a similar problem with the SBC when trying to run that motor at Indy...it would pump the oil out the breathers and starve the engine of oil....dry sump or no. "They" fixed that.

Posted by: ME733 May 4 2010, 10:43 PM

.....oop,s I thought J,P,...that YOU were one of the co-drivers., the sebring race posting was by you ., my bad.

Posted by: ME733 May 4 2010, 10:46 PM

Posted by: DNHunt May 5 2010, 07:39 AM

Ah this is great. Two of my favorite people going at it again in this thread. Just like old times. Both of you guys have been a great help to me, Thanks.

I disconnected and plugged the head vents on my engine and I upped the size of the breather hose to 7/8" inner diameter. This is what I have observed. The oil temps seem about the same, which isn't saying much cause it's been darn cold here. The oil pressure is definitely a bit higher. The VDO gauge shows about 5-10 psi increase on the highway.

I vent the breather box into the air cleaners. There is definitely less oil getting into the air cleaners even though the oil this spring is staying so cold it's foaming like mad. I haven't seen any new oil leaks so I suspect crankcase pressures are about the same.

The most dramatic thing I've seen is an increase in head temps. The heads warm up faster from a cold start and they change more rapidly on the road. I suspect this reflects the fact less oil is making it into the heads to cool them. I have not had a chance to thrash it at the track but I suspect this will be better for sweeping corners. I'm not so sure this is that great for a touring car.

I am concerned that under load the heads will heat up too fast and too much. Last year climbing up the Siskiyoos in southern Oregon at 75 mph on a 70 degree day with both trunks stuffed and two people I maxed out head temps at ~390. Oil temps were fine. I will really be watching the CHTs and I suspect this year when I make the same climb I may have to let things cool off. I'll report back in a couple of weeks. Mind you this is with stock cooling but, Nickies. It is certainly possible that the cooling is just not up to handling the heat generated by a large engine under a big load. It should be a good test though.

I've thought about putting gate valves into the head vent lines and closing them for AX and track time and leaving them open on the road.

Dave

Posted by: charliew May 5 2010, 08:00 AM

Is it not possible to drain the heads to the case? If the level is lower and into the oil in the crankcase the crankcase pressure won't affect the draining. Thats how the suby is drained from it's pcv- vent -turbo drain. It's a cavity in the block that has a tube into the oil in the pan. I am sure if the oil temp is lower than the head temp the oil is helping to cool the heads. It seems to me it is easier to cool the oil than the heads.

Posted by: Jake Raby May 5 2010, 08:13 AM

Dave,
Thanks for your first hand input. I have not noted any differences in head temps with these mods being made but I certainly appreciate your observations. I will continue to pay attention to the data and gather more from the logger. With this being such a hot topic now I am even more driven to more thoroughly understand the scenario and quantify our observations.

The gate valves are an awesome idea. I just recommended that to a customer last week with a 914 AX car that uses one of my engines, he is local to JP and Dave as well :-) I plan on using the gate valve arrangement to help gather data from the arrangement. I even have two electronically actuated valves with the proper size ports that I can use in line to switch scenarios on the fly while gathering data to see the exact occurrences.

An increase I head temps isn't a bad thing as long as the heads are staying in the ranges that we recommend. A head temp of 390 certainly isn't hot in a 914 thats generating 200HP while traveling up a grade like you explain.

The reason I support Len's racing activities is so we can continue to build the breed of components that we use in our street engines, not just to gain notoriety and win races. ALL of the parts in the engine that he has in the car right now are exacting to those that we use routinely in our street, non competition engines and we do that purposely. This even includes the valvetrain components, we use the same valves, springs and retainers in Len's 8,500 RPM engine that we do in a street engine that never turns over 6,000 RPM and just alter the spring pressures. The same valves themselves are used also and at the present those valves, bearings and other "standard RAT parts" in the current engine have been installed for 1.5 seasons of race abuse and got us a runner up in the SARRC last year.

Not many 914-4 race engines making this type of power can be ran for 1.5 seasons at over 8,000 RPM and live to keep performing. Thats not to mention my brutalizing testing regimen that is employed on the chassis dyno before every race when I hold it at 8,000 RPM under full load for 5 minutes at a time. This engine has done it and just 3 weeks ago on the chassis dyno here we made more power with it than we did when it only had one race under it's belt- more power than it has ever made. The reason that we race is to apply the "overkill engineering" that we do our best to develop into an application that is as rigorous as it can be. Len's engine is basically a small (1832cc), high compression street engine with a set of heavy breathing heads.

Posted by: Jake Raby May 5 2010, 08:31 AM

Good idea and we have considered this for street engines. BUT under periods of cornering where the oil in the sump is concentrated to one side of the sump the draining of the heads into that area will be impacted. Since this situation is what we are trying to avoid we have not explored it. It could work in street applications where cornering isn;t as hard or as sustained as in AX or track circumstances.

When the G forces effect the oil level, elevating it above the drains that would be in the case from the heads, the drains would be worthless or could give the oil another path to the heads, thus making the issue worse.

Posted by: HAM Inc May 5 2010, 08:51 AM

I have not seen a difference in CHT's since blocking off our rocker vents. But that could be because Jake spends a lot of effort on keeping the state of tune consistent for changing conditions. Dave I think that if you are seeing an increase in CHT's after blocking the rocker vents then you may have a tuning issue. Oil just doesn't have the ability to pull a significant amount of heat from heads in the volumes that are pumped into the rocker chambers. The springs benefit from cool oil, but considering where the CHT measurement is taken I really wouldn't expect to see much CHT drop from oil cooling.

I will say that if your oil is spending so much time in the rocker chambers that it is cooling the heads, then you have a significant decrease in the amount of oil around your sump pick-up during those periods. I would keep the heads unvented and make adjustments to the tune to deal with the CHT issue.
~390 head temp for a brief period is not bad if it occurs at full throttle, (especially with nickies) and falls back down quickly once you get out of the throttle, or reduce the amount of throttle.

Blocking the rocker vents doesn't change the volume of oil that is pumped into the heads via the pushrods. It just ensures that there are no pressure differentials between the case and the rocker chambers, which allows the oil to return quickly to the case without pressure inhibitions.

I suppose you could route lines from the bottom of the heads to the sump area. Richie Ginther did that back in the early 70's. The issue I see with that is that if the lines don't have a check valve then oil will exit the sump and run up into the outside head in a corner, possibly starving the pick-up. The complexity of a system that would function properly for a high revver (the Ginther 914 redlined at somewhere around 6200) seems like overengineering to me. The original design has tubes for the return of oil, the design just has to optimized.

I have also wondered how many of the Ginther ideas that were published for prepping a 914 for racing might have been discarded later on by Ginther. Mark Donohue said that about 20% of his chassis ideas worked, the rest ended up in the trash. This is why I love the chassis dyno for this type of work. I tried several different breathing methods, none of which worked to our satisfaction, before simplifying our system and going back to very basic ICE engineering principals. Draw the oil out of the lowest place available and breath from the highest point available.

BTW the shop in my area that builds the winningest V8 circle track engines, (My buddy Darrell Gabriel of Gabriels Race Engines) runs a pair of seperate vent lines from high up on the oil pan up to the valve covers so the three chambers can breath without interfering with the oil that is draining back to the pan from the heads. This was the only way they could keep oil in the pan on engines that don't allow dry sumping. It works so well that he now does that to his dry sump engines too.

I have said it before and I'll say it again here. We run no rocker vents, have a single 3/4" vent line running from our chimney. Oil temps are down, puking has been effectivley eliminated and the engine is stronger now (by 3 hp) than it was when it was new. The system is simple and uncluttered. True I am a rookie road racer and running regionals, but the engine doesn't know that. All it knows is that it is worked hard and never runs under 6,000 and each lap revs to 8,000. Use this info or slam it as you see fit.

Posted by: ConeDodger May 5 2010, 08:55 AM

Jake,
Profanity, name calling, weak shots at your reputation aside, this is an informative thread. At what temperatures should we be concerned with the LE heads? Len bakes valve seats out of warn original heads at 400 degrees F.

In a dual purpose engine like mine will be, I like the solution Dave outlined. Something I can switch between for street use.

Posted by: Jake Raby May 5 2010, 09:45 AM

Start being concerned at CHT of 425 peak, but I have purposely taken the heads higher than this with no failures.

Its a shame that we can't share information without conflict, oh wait a minute- we do that on my forum everyday :-)

Posted by: charliew May 5 2010, 09:58 AM

In the suby it's easy to build one way gates in wings in the pan, to work with g forces. Do you think a swinging flapper over a return tube would block the drain from the head into the case on cornering? Also like a lot of other motors the suby has restricters in the heads to restrict oil flow to the valve train. It really sounds like what you've got already works and more parts cost more and there is more to go wrong though.

Posted by: DNHunt May 5 2010, 10:03 AM

Len, my observations about higher and more rapidly rising head temps are with the same tune before I plugged the head vents. I run SDS injection and tune with a WBO2 and EGT so, I can get my tune close. I feel my tune is safe and if anything is conservative on the fuel side. The timing is the same as we set on Jake's dyno. With my gearing and tire combination 75 actual is about 3800 rpms. 3800 rpms fails at the high end of an rpm range that requires less fuel than engine speeds above and below. I've seen that on every engine TypeIV I've tuned. That kind of dip in the fuel table is always the toughest to tune in my opinion. I always feel like it is a compromise and I have found in order to give the engine what it wants above and below this speed this portion ends up a bit rich. The linear nature of SDS tuning is both and advantage and a disadvantage in this case since one cannot tune each individual load vs rpm cell. The advantage is it is simple, the disadvantage is one has to accept a bit of compromise.

It may be that the engine is asking for a tweak in the timing since EGTs are the highest at this engine speed. Very light load (overrun to slightly cracked throttle) will heat up the exhaust.

I will admit that the head temp change is an observation and I didn't quantified it. I put it out there just because I thought it was interesting. It's certainly not a huge change and I wouldn't even worry about it except I'll be doing a lot of climbing with a lot of weight again for WCR and it's in the back of my mind that I better pay attention to head temps. If worse comes to worse I'll pull over and cool it down, richen the mixture or slow down.

As far as the 390 head temp last year, I am able to say that was with an AFR of 12.5 because I could use the SDS tuning knob to adjust it on the fly. I don't remember having to do that however. Again, the timing table was the one from Jake's engine dyno. Temps came down quickly after we crested the summit and I rarely see head temps over 325. Up here in the PNW the biggest challenge is to get the engine hot.

Posted by: Jake Raby May 5 2010, 10:29 AM

Dave, which CHT gauge are you running again?
Yet again, your first hand experience is greatly valued. I appreciate your analytical overviews and your situational awareness- thats how you learn.

What you are experiencing tuning wise with the engine is the difficulty that we always see with perfect tuning at peak torque- the point of highest efficiency with every engine I have experienced. This difficulty exists whether you have carbs or EFI, a standard dizzy or direct fire. It is always the point where the engine is more twitchy with EGT and CHT and where lots of things occur in a very narrow RPM range. Due to this at that point its near impossible to tune the engine perfectly based on the feedback from the vital signs of the engine.

The gearing of the 914 and most popular tire sizes are partly responsible for this. The dip in the fuel curve is also a point where EGT spikes and CHT spikes if the engine is held under load for long enough.

Posted by: Racer Chris May 5 2010, 10:36 AM

I have always run valve cover vents and a single tower vent on my FP race engines - since 1997. I have never experienced any oil pressure related issues.
My breather systems have always incorporated a self draining feature, so loss of oil volume has not been a concern. With 3 National race wins and 3 Regional titles under my belt I must be doing something right.

If the oil temp increases above the desired operating temperature as a result of spending more time in the rocker box it stands to reason that increasing the oil cooling capacity is an appropriate solution, rather than trying to prevent the oil from absorbing more heat. Obviously the oil is taking heat from the heads which is a good thing. I can understand not seeing evidence of the oil cooling effect from reading CHTs under the spark plugs. Those sensors react very quickly to load induced combustion chamber temps but aren't necessarily indicative of overall head temp. CHT readings fall very quickly as soon as one backs off the throttle.

Oil is intentionally used to cool the pistons, so why shouldn't it be used to cool the heads as well?
If loss of oil pressure is a concern from some of the oil being away from the pickup during cornering at AX or track then increase the oil level. The total volume of oil that can be held inside a rocker box is no more than a pint.

Posted by: charliew May 5 2010, 11:44 AM

I'm still stuck on the thought that oil is usable after being in a 360f enviorment. That alone should change the viscosity so much that oil pressure would really fall off. I bet the characteristics of the air cooled head and it's propensity to get hot are very hard to tune on the lean side to make the most power but still be safe.

Posted by: Jake Raby May 5 2010, 12:59 PM

Chris,
Thanks for your input. I had wondered if you ever ran into this issue through your experiences.

The issues we ran into did nothing more than prove that we needed to investigate more deeply and try a few things that have proven to defy what we had previously thought completely.

Yet again, there is no general blanket statement about which is best for every engine, application and arrangement. Had we not experienced what we did with the race engine and had I not experienced what I have with street cars I'd have the exact same opinion that Murray and others have had who have been the opposition in this thread. I tend to be a student of the engine.