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Posted by: worn May 13 2013, 08:33 AM

If anyone has read my previous threads my two week vacation turned from driving to lying on the creeper under the new engine and transmission. Low oil pressure after warm up. I ordered a new Melling 30 mm pump and we shall see, but at the same time I looked into the pressure relief system - especially where it shunts oil away from the cooler because it is easier to see in the car.

What I found surprised me. First, looking at two different cases (72 1.7 and 76 2.0) I found that the piston seats on a shoulder in the bore that is at most a mm wide, and is not at all uniform in width across the piston face. OK, maybe it isn't supposed to seal.

Second I found that by the time you have opened the valve to shunt past the cooler, you are also dumping into the sump. That is there is a small overlap between the outlet to the oil gallery and the grooves cut in the bore leading to the sump exit.

Finally, the piston is simply loose in the bore. I can understand a fear of seizing, but there is no way that with my system oil isn't streaming into the sump, and it will stream faster as it thins - much faster.

I also spent a long time cruising the Samba - they ought to know whats up. What I found is a recurrent theme of new engines built in a variety of ways making low oil pressure. Many people were happy with what I ended up with - 10 psi at idle. On a new engine.

It is steel against untreated aluminum, so wear would be expected, but mine do not look worn - just poorly made. Maybe they are worn and I cannot tell. I got a face full of oil on one attempt at examination, so I may have missed things.

It seems an ideal situation for machining or sleeving during the rebuild, and I actually found a manufacturer of a sleeving kit with a ball bearing valve.

Thoughts ladies and gentlemen?

Posted by: reharvey May 13 2013, 08:57 AM

I've been following your posts about the oil pressure problem because I went through this very same thing many years ago after a rebuild. I tried to find a solution in the way you have but the bottom line was to much bearing clearance. As soon as the oil heated up the pressure dropped off. Hate to be the bearer of bad news but my only solution was to take the motor back apart. You'll find that if you use 20w50 oil along with a can of STP it'll keep the pressure up and you may be able to just drive it for a while. I did for over a year with no problems. Good luck.

Posted by: Cap'n Krusty May 13 2013, 09:20 AM

How is a larger oil pump, which will definitely increase flow, going to increase oil pressure. I agree with the previous post. I may be wrong but, IMO, low oil pressure is a result of insufficient restriction somewhere in the system. That means something out of tolerance, like an OP relief valve, bearing clearance too great, or damage to an oil passage resulting in a leak.

The Cap'n

Posted by: worn May 13 2013, 09:22 AM

Here is a drawing about what it looks like. Sorry I am playing with a tablet pen.

Posted by: FourBlades May 13 2013, 09:22 AM

Keep in mind this is just a guess...

The oil pressure relief system includes a spring and a piston.

The PET lsits 2 springs and 2 pistons by part number.

Could you have the wrong spring or piston for your engine block?

Maybe the spring is just fatigued from 40 years and opens too easily letting your pressure bleed off?

John

Posted by: nathansnathan May 13 2013, 09:24 AM

I've experienced this same thing, low oil pressure on newly built motor. My conclusion after years of thinking searching, etc, the problem for me is wear in the bore of the oil pressure relief valve and oil pump bodies being too small on the newer type 1 pumps.

It was Adrian from headflow masters who really showed me how the relief valve wears. He had made a tool to check them, a screw driver welded to a relief piston. About half way up the bore you feel the groove it gets stuck on. What feels like a little lip with your finger, when the tool reaches that point, you can cock it out by way more than you think.

Different conditions can happen with wear there, too. If the seat isn't holding you will see low pressure at hot idle. Oil seeping by in the loose bore causes problems off idle. There are other ways it can fail, if it becomes cocked in the bore, it either won't open or it won't close depending on which end it gets stuck at.

I was pretty enthusiastic about Adrian's ball valve sleeve insert when he showed it to me. Reviews on shoptalkforums are not favorable, but it is just 1 guy that had a bad experience from what I can see. Adrain said the same, said he'd give me one for free if I let him install it. I was totally going to take him up on it, but didn't make it back down to Vista for like a year after, got a different case going in that time. I am still thinking about the ball valve.

Something that I couldn't figure is if it is knurled on the outside, because that one guy said it was, and that it never would come out, so it it gets screwed up on install the case is trash. It doesn't look knurled in the pic on Adrian's site, though. Still thinking about it...

Posted by: worn May 13 2013, 09:33 AM

I am not ruling out the bearings. They are new, I measured the case lots of different ways - Pawn shops have micrometers that even include calibration standards.

As the Capn says there is oil leaking out somewhere. And while it might be the bearings, it might also be something else. My initial idea was that the pressure relief couldn't possibly be the problem, but I am looking at a valve that has tons of clearances all over - at the non-existent seat, and with at least ten fold more side clearance than any of my bearings. I was shocked at how the thing was made after I looked at it closely. I figured that the idea of the relief system letting out pressure was simply wishful thinking (cannot say I'm not wishful) - but now I am really not so sure.

In answer to the capn. Given some leak of pressure, a larger pump will bring a higher equilibrium pressure for a given size escape hole. So the oil pressure should go up in a system that is below the rated delivery pressure of the pump. If the bearings are loose, this is probably just making the gauge feel better because the oil film depends on close tolerances.

If someone has a shot case, I would love to cut it apart to have a better look at the relief and other parts of the oiling system.

Capn - have you ever seen a case with an inadequate relief bore?

Posted by: worn May 13 2013, 09:38 AM

Yeah Nathan, I looked at that site too. I am way tempted.

It looks like the oil relief system is highly dependent on oil viscosity since there is no seat for the piston. The Welmeister kit seems to solve this by making longer pistons - that also mess with spring pressure. I suspect that the longer piston restricts escape flow more than stock.

I have to say I did not install the Melling pump as it came out of the box. I sanded down the clearances and then had to clean up a lot of sand casting in the flow passages.

Posted by: worn May 13 2013, 01:28 PM

What was the cause of the excess bearing clearance? I would like some ideas before I pull it back apart.

Posted by: worn May 14 2013, 12:56 PM

I found a wonderful post on the Samba in which they tested 100 newly rebuilt VW engines at different temperatures, monitoring oil pressure and flow using both a 26 and 30 mm pump. It is worth reading for most of us:

http://www.thesamba.com/vw/forum/viewtopic.php?t=280293

For me, several parts were of interest. For one thing it shows what happens when you change pump size. So they answer the Capn's question. I am regretting the Melling already, but it was enough work to get in that I am giving it a try. Car is almost buttoned up. Maybe I will end up with lower viscosity oil in the end.

The second part was in a warm engine, they uniformly found low oil pressure at idle - about 10 psi. 100 engines, very low variance.

For me the most interesting part was the design of the pressure relief valve. These were two valve engines, although not type 4. The VW engineers were very careful about how these should be made, and a very clever bevel modulates opening pressure to make it higher than closing pressure. I can say for certain - mine ain't shaped like it is supposed to be! It is either completely worn out, or more likely, never made right to begin with.

I understand there were design changes between the motors described in the article and the ones we run, but read the post, it is completely worth it.

Posted by: r_towle May 14 2013, 02:33 PM

Check the case main bearing seat size.
Check the main bearing thickness.
Check the main bearings in the case all torqued down, no crank.

I recall Jake mentioning that the main bearings halves were slightly large and needed to be hand files down on the top edges to allow the case to close all the way.

Rod bearings may also be having the same issue, not sure.

Pretty sure Jake measures everything with bearings and not with bearings to verify the bearings are right.

With his higer volume of motors, he sure has seen all the wierd product issues coming onto the market.

Just because the bearings are new does not mean they are right.

Rich

Posted by: eyesright May 14 2013, 02:33 PM

FWIW I'm just now rereading the Haynes manual, 6.7, page 20,

"For SAE 30 @ 70C (158F) the pressure at the switch for engine revolutions of 2500 rpm should be 42 psi. If this pressure sinks below 28 psi then remedial action in the bearing circuit or pump is indicated."

I pulled my fresh home rebuilt engine chasing oil leaks at the oil filter mount and rear crank and will post on that when I get it back in the car this week I hope. But I have been following this thread because my pressure seemed low during the 600 break in miles I put on it last month. In my college days driving a VW Bug many miles I remember hearing that an oil light at idle wasn't unusual. Of course it helps to read the manual every now and then so now I'm worried again. And is the oil hot @158F or just on the way to hot if 200F is a more normal temp range.

If I had a direct read oil temp and direct read pressure gauge instead of my electric VDO's maybe I'd feel more secure, and maybe I just need to replace the oil pump while the engine is out....

So I'm keeping an eye on this thread and will add my results

Posted by: worn May 14 2013, 02:49 PM

Thank you Rich. It isn't as though I don't believe I can make a mistake. I work in a checklist environment and I have made many many of them. Believe me, I know I get things wrong on a regular basis.
My worry though is what happens if I take it back apart and there is nothing that I can find wrong in the clearances? So I want to cover other avenues first. The tranny build went just like that, but I spent months on the engine measuring. When I was a post doc at Berkeley my advisor told me something that stuck forever - if you do an experiment and get a result, and then do it again the most likely outcome will be the same result.

Also, the fact that we have data about 100 VW engines is pretty mind blowing to me. No, it is the fact that it is data we get to look at.

Thanks again Rich. The advice I get here is always appreciated.

Posted by: worn May 14 2013, 03:00 PM

Oh I have no problem making more than 28 psi at 2500 rpm at that temp, it is more like 40. But at full warm up, it sinks towards oil light pressure on the electric gauge at 900 rpm. FWIW, when my electric VDO says 8, my mechanical one from VDO on the case says 15, if that means anything. In the TR6 I just built I get way more than 15 at idle. So I am worried, and it sounds like I should be.

It is worth looking at the Samba article though. The valve illustrated looks quite functional. But the one in my engine contacts the plunger in a rim that does not exceed the chamfer of the plunger (which you can hardly see). I did prussian blue and it marks a shoulder about a half mm wide all around. The case from the motor I am replacing has a contact ring of about 2 mm all around. Neither seems like a great sealing surface for hot oil.

Again, if there is a junked case out there, I would like to dissect it with my band saw.

Posted by: yeahmag May 14 2013, 03:14 PM

Interesting for sure:

http://www.headflowmasters.com/vw-oil-pressure-valve-body.html

Posted by: reharvey May 14 2013, 03:28 PM

I rebuilt another motor to replace the one with oil pressure problems. Years later when the old motor was torn apart we found that the # 3 main bearing was a mess. Don't know what went wrong but it had deep grooves in it and was worn out. By the way--I tried the Melling pump in the old motor and it made things worse. The oil pressure was lower than with the stock pump. Ray

Posted by: worn May 14 2013, 03:39 PM

Thanks. I am interested in doing a post mortem on the 2.0 I took out to see what the deal was. After several autocross runs the OP would poop out. No problem getting to the event though.

Posted by: r_towle May 14 2013, 03:44 PM

So , I appreciate that you measured quite a bit of the motor, but what I am asking is not typical.

Did you measure the roundness of the main bearings mounted in the torqued case with no crankshaft in place?

This would produce an oval measurement if the bearings are as Jake has found some of them to be, which is to large.

Did you do the same process to the rods on the big end, bearing in place, measure for round.
Again, same condition, same results.

Using an internal bore measuring device, done in a systematic way will produce the results of round or oval...

Just putting that in the back of your mind...again, its not a typical thing to ever do when building a typical motor...but with Jake finding these bearings coming from the factory to large, I now do this extra set of steps just to be sure.

Mind you, I build maybe two a year....
Jake builds alot more, so he will see more issues.


Lastly, I would look into the heavier spring and new piston for the pressure relief system.
http://vwparts.aircooled.net/Bugpack-Oil-Pressure-Boost-Kit-1970-Dual-Relief-p/3041.htm

Not the exact part, but call them, they are cool and they have the right one...
I would go for that...20 bucks that may help..

Rich

Posted by: worn May 14 2013, 09:16 PM

Thanks for the in depth reply. The answer is often but not always. With the round bearings on the mains I quickly found that plastiguage wasn't gonna help. So I did measure roundness mostly with a set of snap gauges and an internal mic, not the ideal tools.

I won't have the hard data for a few days but tonight I found what appears to be the smoking gun. How much smoke remains to be seen, but it looks to me like folks are underestimating the complexity of the relief system, and that may extend to factory machinists. At this point I can clearly say that at high temp my oil relief should have been sendinding oil all to the cooler. It was instead bleeding oil into the sump at a rapid rate. Nothing to do with the pistons or the springs, but instead either case wear or sloppy machining. Look at the samba post - it is an eye opener about where and at what pressure oil in this class of engine goes.
I cannot thank you and others enough.
Warren

Posted by: cary May 15 2013, 06:00 AM

Did you get a case yet?

I have one that had a hole blown out the side where the PO or wrench forgot the slotted oiling washer under the distributor.
I JB welded the case after it was out just to see how it would work.

I'm pretty certain I have both halves. I'll look tonight. I'm heading to the shop to collect my backpacking gear.

Posted by: r_towle May 15 2013, 07:17 AM

So, now what are you planning to do?
Not sure I understand what you found or what the cure might be...
Very curious here.

rich

Posted by: worn May 15 2013, 12:08 PM

[/quote]

So, now what are you planning to do?
Not sure I understand what you found or what the cure might be...
Very curious here.

rich
[/quote]

Well, I figured this was worth documenting so I am making a cast of the relief cylinder so that people can see the problem. The problem is working upside down and not contaminating the motor.
What I found was that the piston does not reach the seat because of a raised shoulder about 2 mm above the seat. Maybe they cut the seat and the chamfer with two bits and the ridge is where the boring didn't go down quite far enough. My other case does not have this problem, but also shows evidence of careless manufacture - the chamfer is too big. The system is more complicated and elegant than it looks - the diameter of the chamfer sets the opening pressure. Because the chamfer diameter and the bore diameters are different the opening and closing pressures can be different. Cool. I doubt most factory machinists recognized this.

IF it ain't bearings, and I get rid of the ridge by careful boring, then I should have big pressure when I start it up again. If not, I fold and tear the engine down. More later when I know. Fingers crossed.

Posted by: r_towle May 15 2013, 09:46 PM

Please post some pics of what you are doing.

Posted by: worn May 16 2013, 08:44 AM

OK, I am making some progress. If the bearings are loose, this will be a bit of an extra, but that hasn't been tested yet.

It is hard to show, but here is what I found:

The first image shows a comparison between the Prussian blue rub off in my old worn out 2.0 and the new 2056. The pistons are identical.


You can see a clear seat in the old, but you can hardly see contact with the new. In fact, there is a small rim around the chamfer where dye has transferred.

OK, getting a photo of the cylinder was tough. Here is my best and it shows the problem:


The green arrow shows the offending ridge running all round the circumference of the cylinder. A slightly smaller final bore perhaps? At any rate, that is what stops the piston a couple of mm short of the seat. the line between the pressure bevel and what is supposed to be the seat is shown with the other arrow.

What I did was to get a piece of scrap iron. It should have been steel - I made a bad choice based on what was lying around and made a cutter at 15.9 mm. It is shown below with a before and after prussian blue test. I used grease to catch the swarf, which in my case was a very fine powder - like anti seize. At first I thought this would go quick, but it took quite a lot of turning the tool because basically the tool I made is not at all aggressive - it dulls fast and there was purposely no relief cut for the cutters.



I have to rinse well, clean like the dickens and get it back off the stands to find out how things go. Since I changed two variables at once with the new pump, I will never know. What I can say is any oil that gets by the piston is back to the sump. The bores tend to wear and there is nothing to stop it but viscosity at the valve. So if as I suspect the valve wasn't sealing, I would expect what I found. Low pressure with hot oil.

Posted by: nathansnathan May 16 2013, 09:05 AM

aircooled.net used to rent out a 5/8" end mill to dress the seat as you have done there. Pretty bold, making your own cutter!

It's weird the poor attention to detail the factory had for this mechanism. I have seen pics where there is a stamped VW logo on the face of the piston, right on the edge interfering with the seal.

-Seems like cleaning the bore up though, might let oil get by when it is off idle. I've been tempted to use a reamer to oversize the bore, but would want to turn a new piston. Shoptalkforums awhile back, we came to the conclusion the best thing to turn a new piston out of would be "Torlon" which is a high temp lubricating plastic, like high temp teflon. Pricey, but it would never wear a ridge in that bore again.

Posted by: worn May 16 2013, 09:24 AM

That's funny - both of the pistons shown have a small VW stamped on the mating face, but very small. Also they used a bench grinder to dress away the piston cutoff nub from the lathe. The system is brilliant, but vulnerable to wear and I think in my case poor construction. You may get something you like, but you won't get the sophistication with a ball valve. Might solve the headache though, I dunno. Can't wait to get it back on the ground. The turbo tie rods will have to wait.

Posted by: FourBlades May 16 2013, 01:21 PM

You have done a very systemmatic investigation of the relief system.

Nice job!

John

Posted by: brant May 16 2013, 01:59 PM

This is what I described in your other thread
it may not be the factory attention to detail.
I think you would find if you cut a case open and inspected the surface that often shrapnel from a previous engine melt down can cause this problem.

I've used an old piston in the past with valve grinding compound.... (and lots and lots of time manually hand turning it) to clean up the face.

your tool looks better and quicker

Posted by: yeahmag May 16 2013, 02:08 PM

Just to refresh my memory, you are trying to get more than 10PSI at hot idle? If that's not it can you remind me of what condition you are trying to cure?

Posted by: r_towle May 16 2013, 04:52 PM

Interesting.
Might be worth getting a custom piston made and reaming the hole out just a bit larger....

Posted by: Jake Raby May 16 2013, 09:31 PM

All these rules and myths change when bearing clearances are altered. I prefer to move a higher volume of oil through the engine and to do that requires a higher volume oil pump and altered internal clearances.

There are no rules, if there were I wouldn't enjoy it so damn much.

Posted by: worn May 17 2013, 09:10 PM

Replying to Jake and Yeah.
I was worried that 10-15 psi at hot idle was too low for a new engine. That is what started it. I will find out tomorrow and if it worked will start tuning my mps - the horror.

What I think is interesting is we have numbers for bearing clearances, suggested tolerances for oil pump lapping and lash, but nada, zipperino, nothing when it comes to the system that is designed to actually control oil pressure. I had to hunt for diameters and spring constants and never found them.

So, I will post cylinder head and oil temps, rpms and hopefully oil pressure. And God willing I won't pop the cooler instead. This ruined my vacation and added stress when really, I wanted seat time with the world flying by my narp.

Posted by: nathansnathan May 18 2013, 06:53 AM

The specs are as follows, from the Porsche 914 Technical Specs book
Spring for oil pressure relief valve length loaded: 39mm, on installation new 6.8-8.8 kg (15-19 3/8 lbs lbs)
Oil pressure switch opens at 6.6-8.8kg (2.1 -6 psi)

I don't see bore sizes anywhere, possibly 16mm bore?

Posted by: worn May 19 2013, 08:53 PM

And of course springs mean nothing without the area of oil pressure they push against.

But I digress. Back on the road to full temp on a warm day. I made about 20 psi at idle with 10w30 oil. Not the Oil I would normally run, but I was worried about hitting the oil pressure trifecta. Bottom line, I see no reason to tear apart the motor now, I have the case I just pulled out and it shan't be wasted. A swap may be in the future.

I think the lesson to be learned is to check everything including bearing clearances, and not forgetting oil relief.

I learned another lesson as well. You cannot tune the factory fi without both an inductance meter and an a/f gauge. You may shy away from pbanders warning that all inductance meters aren't alike, but I scored one from ebay for 30-40 dollars that works like a charm. As with Ohms or Farads, Henry's are standards. A little change makes a world of difference and while the result are obvious on the air fuel gauge, it isn't from the seat. My goodness, what a sweet engine.

Posted by: worn May 19 2013, 08:57 PM

And I should add. Buy the DVD if you must, but the tranny rebuild is just what the Dr (me) ordered. Being able to count on shifting is so cool. You either know what I mean, or things are working the way they should.

Posted by: yeahmag May 19 2013, 09:23 PM

So you went from 10PSI to 20PSI at idle with all things being the same?

Posted by: 396 May 19 2013, 10:09 PM

Sub as its very interesting read.
After reading this, I pulled out my clean case. Looked down the by pass area and noticed that there's a ridge on one side. I measured the other non ridge side. The difference is .25mm. Ridge measures 72.25 non is 72mm.
Since this has been my long long over due project, can some one direct me to a shop for such a tool to clean out this ridge?
Thanks for the education on these type 4's

Posted by: cary May 19 2013, 10:29 PM

I learned another lesson as well. You cannot tune the factory fi without both an inductance meter and an a/f gauge. You may shy away from pbanders warning that all inductance meters aren't alike, but I scored one from ebay for 30-40 dollars that works like a charm. As with Ohms or Farads, Henry's are standards. A little change makes a world of difference and while the result are obvious on the air fuel gauge, it isn't from the seat. My goodness, what a sweet engine.


Wasn't it amazing when you dialed it in with the A/F meter/gauge.

Posted by: worn May 20 2013, 08:41 AM

Well, I am still breaking it in. I fixed the odometer so not only do I know the mileage of the car I can count down to 500. With that said...preliminary results are way promising!

Posted by: worn May 20 2013, 08:45 AM

No, I changed to a thinner oil too. I agree though, I expected more - that is why I went with the 30 weight to start up with. At this point when I change the oil I am going with a heavier oil from a reputable company and just drive it. It is a summer car. I think I won't see the oil light and will be able to enjoy the car. New bearings and excellent journals, but the case - well I am not sure. Bearings - well maybe they aren't right. I just don't know, but my mood has improved.

Posted by: eyesright May 20 2013, 10:01 AM

My (home rebuild) engine is back in the car, oil leaks from bad oil filter/case seal (D'oh!) and flywheel O-ring cured...pools of oil on the floor reduced to only a drop here and there.

I also changed the stock oil temp sender to the appropriate sender for the VDO gauge (miscommunication with the guy taking my order @ PP probably, whom I thought said just use the stock sender) so now I have oil temps, oil pressure, and head temp.

Okay, oil pressure is way low (less than 5 @ idle, 15-20 @ speed but 80 when cold.) and on my first drive last night (probably 70F outside temp) my oil temp worked its way up to 225F. So, higher than normal oil temps and lower than normal pressures suggest I'm losing pressure as the relief valve allows oil to return to the sump instead of passing to the cooler. I'll get some marking solution to see if that's the problem and probably figure out a way to hone the seat. I understand I don't want to take off too much, maintaining the chamfer

Warren, thanks for your research and work. If not for that and the gauges I bought just to be cool, my engine would be toast soon.

Tim

Posted by: 396 May 20 2013, 10:16 AM

Pm sent on tool. Thanks

Posted by: r_towle May 25 2013, 11:49 AM

you got 10 psi from honing the relief bore?
Did you change the oil pump?

Rich

Posted by: eyesright May 25 2013, 06:49 PM

Warn

I located the relief valve seat by looking up the bore. It didn't make sense the times I inspected it before, tryiing a spacer under the piston, different spring, honing the piston top, etc. but your photos and explaination made it all clear.

So I got some marking fluid which showed a bung on the seat. The seat, incidently, appeared at most to be 1 mm on one side and probably 2mm on the other. for what ever reason, the bores didn't apper to be concentric. In any case, just a small seat like that actually is a comparatively large area since its on the outer circumference and should make a differrence in opening and closing pressures.

So with wet/dry paper glued to the top of the piston and trimmed to the bore, I spun it by hand against the seat. I ended with 600 grit and the seat shined! Nice and smooth.

So I run it and ....same low oil pressure, about 5 @idle, 15-20@ speed and oil temp slowly climbing to 220F. Went Ace hardware and found a stiffer spring, the gauge was about 20% larger and it was 1 cm longer. Maybe under heat it faded but anyway...., same pressures and temp!

Well, shucky darns! So my options are still

!) clearance problems

2) pump problems

3) some other relief/regulator problem

4) cheap gauge/sender

5) or NO problem... VW Porsche made this one this way and its going to run like crazy for 200K miles. I've put 1000 break-in miles on it now and my know-it-all advisor/pal says I if it was really a problem I'd probably know it by now.

I think I will order a new piston just to rule out the piston bore being part of the problem. Any comments anybody?

Posted by: 76-914 May 26 2013, 07:53 AM

Verify your "cheap gages" or you'll be chasing your tail. It's the same as trying to tune your engine w/o an AF meter. Hit n miss.

Posted by: worn May 26 2013, 09:13 AM

I got five to ten in the end. So I am at about 15 at idle. I can easily make the Porsche manual spec, which is stated for 70 degrees c. But I am at more than 110 degrees c. That still leaves me in the white with the new style gauge, or probably wher the beginning of red used to be. The pressure runs strong until about mid gauge. So the first twenty minutes are great. Btw cooling system works like new.

Now I am worried about cylinder head temps vdo under the spark plug. Going up hill, and hills are gentle here, at 65 brings me quickly to 400 plus. I went with 2056 and calculated 8.5 compression and am about ready to indefinitely jack stand my 914.

Posted by: yeahmag May 26 2013, 09:44 AM

The VDO CHT is not temp compensated. You have to do math to use it. Switch to an M1000 from Aircraft Spruce. I love mine!

Posted by: r_towle May 26 2013, 02:30 PM

Per post above me here, what was the ambient temps outside?
What is your timing set at for full advance?
Type of fuel used?

All three affect the temp reading.

Test with better fuel.
Test one degree at a time as you reduce overall advance at 3500 rpms.

Between the fuel, your type of plug, and your advance, you should be able to dial it in for your elevation and climate.

Rich

Posted by: eyesright May 26 2013, 03:19 PM

worn

I agree with yeahmag. My VDO CHT shows 350F. Len Hoffmann did my heads so I wasn't too worried while I sorted out some other stuff. Then I got an IR thermometer which showed 200-210F inside the tin on #3.

Like 76 says, verify. I'll dump the temp sender in a pot of boiling water when I get a chance. Then I want to try different gas grades. And do the same with the oil temp sender at the next oil change. And double check the IR thermometer too. And after all the stuff I've done behind you I wasn't TOO worried but I have a direct reading pressure gauge that I'll hook up.

If I was serious I'd spend the bucks on aircraft stuff ....good advice. Mine's a driver. The VDO's look good and I just want to calibrate and look for consistancy. But I may put some greeen and red stickers on the gauges. That'll make my aviation buddies smile.

Posted by: eyesright May 26 2013, 04:35 PM

PS Worn, oh yeah, one more thing. When you open the engine lid after a run, does it SMELL and FEEL hot?

I had my cooling flaps hooked up wrong once on a prior car and when I got back from a short break in run I could tell things were not right. This was a stock car with no gauges. It just SEEMED too hot. And I knew I didn't understand the cooling flaps when I put it together so that's the first place I looked into. Figured out the error of my ways and set things right and ran it again. The engine bay was hot but a "normal" hot.

My gauges are/will be good information but my engine runs smooth, starts hot or cold, plugs look good, doesn't ping on regular even when I floor it @2000rpm, and when I open the engine bay after a good run it smells and feels normal. (Hoffmann heads and case decked, Raby 9550 cam kit, 2.0L, FI)

I'll keep looking into the gauge readings, but mine's been on jack stands too long and too often. The next time it takes an indefinite rest on jack stands it will be because of REALLY bad news. I hope I don't have to eat my words here on the forum but so far my engine runs well enough that I think I am enjoying worrying it just enough to keep looking as I DRIVE!!!!

Good luck and keep posting. I'm getting good ideas from you and the rest of the posts.