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Posted by: 767driver Feb 26 2017, 03:28 PM

Hi guys,

Lurked here for a number of years and have finally landed a 914-6. It's a 1970 with it's numbers-matching case running a (stock?) 66mm crank and 86mm pistons for a displacement of 2.3L. It runs Solex cams and 40 Webers. It's only got about 600 miles since rebuild. So the engine is somewhat upgraded but nothing too wild.

When I drove it the 45 mostly-highway miles to my house I noticed it was getting a bit warm. The weather was about 60 degrees. The indicator on the factory oil temp gauge was reading about 3/4. The next day I took the car for a nice "getting acquainted" kind of run on mixed highway and country roads. After 25 minutes on the highway at 80 mph and about 3500 rpms it was getting really warm...almost touching the hashed red part of the hot end of the scale. I immediately went over to a buddy's shop and shot an IR thermometer at the rear of the oil cooler. Got temps of 220 or so at top of cooler and 250-260 at bottom. The cooler still has a Stoddard Porsche decal on it. I checked and the cooler is the $1335 German-made part. Oil quantity ok.

Now I know this is not enough motor to overload the factory oil cooling assuming everything is working correctly. I took the thermostat out of the car and performed the pot-of-hot-water-with-thermometer-trick and verified it opens and closes as it should. I guess the in-dash gauge could be wrong, but the IR thermometer seemed to confirm the high reading. All the tins appear to be in place. I have read the cylinder baffles can be installed upside down causing issues. And that the cylinders themselves can be installed upside down. I guess that new-ish oil cooler might be defective...that's an engine drop...right? Ignition timing, cam timing, fuel mixture need to be checked. And none of the cabin heating air tubes are on the car. The 2 supply ducts off either side of the engine cooling fan duct are capped. Is the fact that no fan air is going through the heat exchangers causing the one under the oil cooler to run hot enough to cause the high oil temps? ANSWER: YES

So...what have I forgotten or overlooked here. I had 2 VERY knowledgeable Porschephiles tell me that barring an oil cooler issue it is almost surely a hot bearing (youch!) making that kind of heat.

Any thoughts or ideas are appreciated.

1970 914-6
VIN 9140432125
Engine 6405400

Posted by: PlantMan Feb 26 2017, 03:38 PM

Better post some pics cause most of us want to see the car first!!!!!!

Posted by: PlantMan Feb 26 2017, 03:39 PM

BTW congrats on the car!

Posted by: Perry Kiehl Feb 26 2017, 03:51 PM

260* is too hot, but you can get a spike in temp after you shut the engine off.

It's possible with the performance upgrades you'll have to add additional oil cooling. From my limited experience mag case engines require additional oil cooling in a 914 once you get over 150 hp or so.

If I suspected a failing bearing, I'd drain & strain the oil and cut open the oil filter.

Posted by: plays with cars Feb 26 2017, 04:11 PM

Check your ignition timing. Should be ~32-34 at 6,000rpm with the vacuum disconnected and 4 ATC - 6 BTC at idle depending on whether or not the vacuum retard is still intact and working.

If its too retarded it will cause the engine to run hot.

Posted by: jfort Feb 26 2017, 04:22 PM

Mine ran too hot and it was tuned correctly. I put in a front oil cooler. Problem solved.

Posted by: mskala Feb 26 2017, 04:58 PM

I have almost this exact setup. My cams are Dougherty Cams DC-30 which is a
modernized Solex-type cam.

If you are using the 914-6 (911T) distributor it's not going to be correct. I'm using
a 911E/S distributor with 30-32 degrees advance. There is no vacuum advance
obviously.

What settings do you have on the carbs? You could be running lean.

Maybe your fan air deflector behind the alternator is pointing the wrong way?

Yes, cam timing can cause extra heat.

It is possible to remove the oil cooler without removing the engine but it's not
worth the extra effort.

Do you know exactly what the heads are? Not that they would cause the problem
but the settings on ignition and carbs I use wouldn't be good for you if the heads
are not 2.2L basic heads.

Posted by: mb911 Feb 26 2017, 05:06 PM

I have a similar engine I am building though mine started as a 2.4t and now is a 2.4 with ported heads 2.2 s pistons and soles cams. I will use a front oil cooler.

Posted by: BK911 Feb 26 2017, 06:12 PM

If the car sat it could have mice nests on top of cylinders.

Posted by: gereed75 Feb 26 2017, 07:36 PM

Timing will have a dramatic effect on cylinder head temps. Advanced timing will cause higher CHT's, especially with higher compression ratios

Richer mixtures can also help reduce CHT's. the correlation is obviously lean mixtures raise CHT.

Higher CHT's equate to higher oil temps.

I run a 2.4 with the D.C. 30 cams and 9.5 CR 32 degrees advance on a T distributor. I ran a wide band O2 sensor to tune the webbers and it runs a bit on the rich side (pretty much in the 11-12 AFR under any load). With the stock 6 oil cooler the Temps runs around 180 -220 with normal street driving. Hard driving does elevate temps quickly on hot days.

No reason you should not expect about the same. Check the timing before getting more serious.

I am installing a rear mounted cooler with fan and ducting to pull "cool" air from the wheel well so hopefully I can run it without restriction.

Posted by: rgalla9146 Feb 26 2017, 08:38 PM

Have you checked the fan belt ?

Posted by: Rand Feb 26 2017, 08:40 PM

I thought he was talking cooling, not alternator? (Ah yes, 25 or 6 to 4... Never mind, I was thinking direct impeller like the 4s.)

Posted by: mskala Feb 26 2017, 09:04 PM

Also I did some experiments and running without a deck lid lowers the temp
at least on the highway. So getting one of those GT lids with all mesh should help.

Posted by: sixaddict Feb 26 2017, 09:17 PM

something up...should not need added cooling at current temps

Posted by: porschetub Feb 27 2017, 02:15 AM

All the right answers from many,but the OP has failed in posting anyway the key points he hasn't completed are the main reasons for overheating,1970 engine is most likely running Weber's as per stock jetting ...don't know cause he didn't say,they are set lean from day one,the increase in displacement will only make that worse (lean condition) ,timing is very important also 34 degrees @ 6000 and no more.
I would say he will maybe have higher compression and that adds to the problem as mentioned.
I have a slightly modified 2.2T stock Marelli dizzy set slightly retarded and run 185 to 190 in hot weather,had a shifter linkage issue and limped home in third gear got to 200+ due to slow fan speed.
Oil pressure is a great test of running temp in these motors,they get hot it drops fairly fast.
See no point in pulling the oil cooler that won't fix anything,not that hard to do ..ask me how I know,no need for a front cooler in a motor that size.
Think the OP should provide all info then some full answers will be forth coming.

Posted by: Perry Kiehl Feb 27 2017, 07:47 AM

To summarize in order of ease:

Check fan belt.

Confirm gauge accuracy.

Drive it hard with the engine lid off.

Make sure the timing is dead on the nuts, in particular not excessive advance.

Check the air fuel ratio to make sure you are not too lean, too lean=higher temps.

Check for mechanical obstruction of air flow (mouse nest on cylinders/ oil smeg).

Posted by: rgalla9146 Feb 27 2017, 08:09 AM

Advanced timing will lead to hard cranking and pinging.
Retarded timing will lead to elevated temperature.

By the way....your car is beautiful !

Posted by: forrestkhaag Feb 27 2017, 10:55 AM

Beautiful acquisition. My favorite color

You may want to consider the simple installation of a Carbon Fiber-fiberglass engine access hatch. This kit makes addressing several of these issues very easy to check. as well a routine 6 maintenance.

i.e., belt tension and changing, timing mark visuals, dizzy adjustment for advance/retard issues, inspection of alternator cooling fin direction, etc.

The photos are using my type four engine to show how much of the firewall is opened up for a 6 installation / my 6 goes in next month so I will update photos.

Good luck with the overheat issue.




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Posted by: toolguy Feb 27 2017, 11:35 AM

Timing. . mixture/carbs. . or this. . . all the missing pieces from the previous owners car cover were finally located. .


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Posted by: 767driver Feb 27 2017, 01:26 PM

Thanks for all the replies...and keep them coming!

Some of my thoughts and responses...

I hear the calls for a front-mounted oil cooler. I really don't think, based on all I have read/heard/seen over the years, that this particular engine should need another cooler. I could be wrong...but it's just not that much more motor than the stock 2.0

Ignition/distributor and carbs are all on my short list. This car was "dyno-tuned" at a reputable shop before I bought it...probably within the last 12 months. ALL of that should have been set up correctly. Will verify...

I have seen ZERO evidence of rodents. Having said that, the air flow through the fan housing and engine tins/baffles will need to be checked free and clear.

The belt seems properly tightened by deflecting it with my finger. It sounds like it is turning at the proper speeds when driving (based on my "ear" for my 911's engine sounds).

This car already has the replica 916 double-grilled engine lid on it.

Oil pressure was mentioned by user id porschetub. There is an auxiliary gauge pod installed containing an oil pressure gauge. The engine has 60PSI or a bit more when cold at fast idle. It slowly looses pressure as the temp rises. It was showing 30PSI at about 3000rpm when the oil was real hot.

Gauge accuracy... is there a better way to verify that than pointing an IR thermometer directly onto the oil cooler itself?

And finally the firewall engine access hatch mod was discussed. I am not sure I want to cut an original 914-6 for the added convenience...which is significant...of that hatch.

I think my first action will be to perform an oil change and look for rebuild-related swarf in the sump screen and oil filter.

Posted by: porschetub Feb 27 2017, 01:35 PM

You would hope that the OP's engine builder allowed for the extra displacement when rejetting the carbs,I don't have webers but I know on the 914/6 and 911 carbs of that era the idles ,mains and vents were small much like the jetting in the latter zeniths.
Perrys comment about bearing is a valid one, cases are sometimes torqued up without checks for free rotation of the crankshaft,also were the rings "gapped" properly in the pistons ?,have the valve clearances been rechecked after the initial ''run in'' ?,I would suggest that the OP limits driving the car and returns it to the engine builder asap.

Posted by: porbmw Feb 27 2017, 01:38 PM

There are far more knowledgeable persons than I who have already weighed in on this.

However, there may be one other means of helping to lower engine heat...by increasing air flow...by using the two air deflectors that later models of 914s were supplied with...If I recall correctly, in around 73/74...affixed to the underside, one on each side of the underbody, just in front of the engine

Posted by: porschetub Feb 27 2017, 03:41 PM

Yea good point,I believe they really made a difference.
Not sure in this cause perhaps things are a little deeper .

Posted by: 767driver Feb 27 2017, 04:14 PM

I know these exist, but have never seen them. Anyone have pics or a source for the parts? Apparently they help create a low pressure area under the engine bay thereby increasing the total airflow through the engine bay.

Posted by: mskala Feb 27 2017, 04:20 PM

If you want to check the various gauge components:

Posted by: rgalla9146 Feb 27 2017, 05:18 PM

An additional oil cooler should not be necessary on an engine of your displacement and state of tune.
Hole in firewall ? oh please !
If your car does not have an original (914 6) flywheel mark the one you have at TDC and use an adjustable timing light to
check proper timing.
There are various methods for determining true TDC

Posted by: Cairo94507 Feb 27 2017, 05:54 PM

Here they are. I believe they came standard beginning in '73. I am adding these (I know, my Six did not come with them) on my car because it can't hurt to get a little more air flow for the motor.

Posted by: Justinp71 Feb 27 2017, 06:40 PM

Hmm, I wondered what those were for. I guess these help because at higher speeds the flow across the bottom of the car is too strong for the air coming thru the engine to merge? Does anyone know?

Posted by: Justinp71 Feb 27 2017, 06:48 PM

In 60f Weather on the freeway I'd think the car should stay under 200f Oil Temp.

How does the engine run? If its lean with carbs I'd think it wouldn't feel very smooth in transition from idle to mains.

I'd also look for a blockage in the air system or a slipping/bad belt like others have mentioned.

Does it have a 5 blade fan?

Maybe the wrong belt pulleys were used and the fan runs too slow? If that was the case you'd probably have an alternator problem at night when the lights are on.

Posted by: 914forme Feb 27 2017, 07:41 PM

What RPM is your engine turning on these highway runs?

I do believe there was a reason the factory installed a Z gear in fifth instead of the ZD in the -6.

It is about a 200 RPM difference, not a huge deal, but at low RPM that 200 RPM could make a difference. Especially if you are bogging the engine a bit.

What happens when you drop down into 4th?

Posted by: toolguy Feb 27 2017, 08:02 PM

Increased cooling with the higher RPM's is exactly the reason the factory used the Z 5th in Six's. .
Have you checked you oil level when the motor is hot. . full 9 quarts?. . 30 psi at freeway speed is low.

Posted by: billh1963 Feb 28 2017, 02:37 PM

My CIS 2.7L runs on the cool side (I posted about it a couple months ago). You shouldn't need an external oil cooler.

Installing an AFR gauge will tell you if you are lean

30 psi at 3K rpm is still within accepted norms (10 psi per 1K). However that is for a more worn 911 engine. I think he should see higher.

But, if his oil is running over 220F he absolutely would see lower oil pressure even with a recently rebuilt engine.

Posted by: Dave_Darling Feb 28 2017, 02:48 PM

Something like that. The flaps create turbulence behind them, which is slightly lower pressure than the other ambient air. That lower pressure helps pull air through the cooling fins on the engine.

It's not a huge effect by any means, but it is there.

--DD

Posted by: 767driver Feb 28 2017, 04:24 PM

I haven't driven the car in a couple of days and it's new to me so I am going from memory here...

I want to say the RPMs are about 3500 at 80mph. The PO said the car had airport gears in it and that he did not like the high RPMs on the highway. Said he replaced 4th and 5th with normal gears. Don't know what those are but I can tell you the RPM drops a full 1000 going from 3rd to 4th...that seems like a lot. And 5th is pretty tall now. Also car is said to have a 930 LSD.

Posted by: 767driver Feb 28 2017, 04:43 PM

And now I have found this thread...see posts 5 and 7.

http://forums.pelicanparts.com/porsche-914-914-6-technical-forum/67345-914-4-vs-914-6-gear-ratios.html

Damn...could it really be that simple?? ANSWER:NO... I drove the car at highway speeds using 4th instead of 5th...still got hot.

Posted by: gereed75 Feb 28 2017, 05:10 PM

Rgalla, not trying to be argumentative or steal this thread, but how does retarded timing increase temps??

My understanding is that timing advanced beyond optimal increases peak internal combustion pressure. That higher pressure results in higher heat and reduces engine output.

What mechanism/physics makes retarded timing produce more heat/higher temps??

Posted by: 767driver Feb 28 2017, 05:11 PM

And from the owner's manual graph you can see 3500RPM should be 75MPH. My gear seems taller...I will have to drive it again to verify.

Posted by: mskala Feb 28 2017, 09:21 PM

Don't assume speedo and tach are super accurate. Also, those graphs would be
true only with the original tire diameters.

Not to sound like I'm putting down your car, but really it looks like you have so
many unknowns that there is no way to even come up with a reasonable guess
at what's going on over the interwebs. I think you're in for a lot of local
investigation.

Why did somebody have an engine rebuild then sell the car without driving it? (you
said it now has less than 600 miles). There are shitty engine builders and/or
mechanics out there.

Posted by: Kansas 914 Mar 1 2017, 09:02 AM

Posted by: rgalla9146 Mar 1 2017, 11:07 AM

Retarded timing allows partial combustion pressure to escape through the opening exhaust valve which raises cyl. head/ oil temp.
There is more to it than that.
Google ignition timing vs. engine temp

Posted by: gereed75 Mar 1 2017, 03:08 PM

Ok I can see that. Knew EGT would rise and that could certainly Raise CHT's.

With all of the other stress that can be caused by overly advanced timing and excessive high ICP, erring to the retarded side seems to be better than high as long as performance is good.

Think I would try for 32 max on OP's (and my) engine.

I have seen two degrees of retard drop CHT's 30 degrees on a fully instrumented (CHT, EGT, RPM, MAP, fuel flow) air cooled Lycoming with no perceptible drop in power.

Posted by: Justinp71 Mar 3 2017, 04:35 PM

If it only has 600 miles on the motor, maybe it still has a warranty? Will the engine builder shop help you out?

Posted by: Wdunster Mar 4 2017, 09:13 AM

I am running a 2.4 e cams 9.5-1 compression mag cased 6 with scolex carbs. It ran hot as well with additional air through a GT Style engine lid. It would get to 212 to 230 in the summer. Added an oil cooler in the back with a fan and it definitely helped. I still keep a watchful eye on it.
B

Posted by: 767driver Mar 21 2017, 05:42 PM

UPDATE:

I might have found the answer today...

After I first posted this thread, I kept digging into forum searches and the interwebs... hoping for that golden nugget of knowledge. Talked with some very knowledgeable folks and bounced some ideas all around my group of gear-head buds. I was getting ready to send the car to a local Porsche shop and start the process of chasing the gremlin$.

One of the things I noticed about my car was that the PO had capped the ducts that take cooling air from the engine fan and duct it to the heat-exchangers. The black corrugated hoses were not installed either. It had occurred to me that this might just make the heat-exchangers (HE) hotter than they would normally be. When the hoses are installed there is always air moving through the HE when the engine is running. The air goes through the HE and a diverter valve where it either enters the cabin heating system or simply gets vented to the atmosphere. Without air cooling those HEs they get damn hot. And the driver's side HE is right under the oil cooler.

So I removed the 2 caps from the fan shroud, connected the black hoses, 1 to each HE, and went for a long drive.

Here are the results...before and after. The first pic was taken on a 60 degree day a few weeks ago. The second pic was taken March 21 on a 58 degree day. The gas level is reading the same only by coincidence.




And some good info here, particularly posts 6 and 7...

http://forums.pelicanparts.com/porsche-911-technical-forum/636233-what-do-you-when-you-remove-heater-but-not-heat-exchangers.html

Lesson learned... heat-exchangers need air moving through them at all times!

Posted by: 767driver Mar 21 2017, 05:44 PM

A picture (not my car) of a heat-exchanger with the proper connections. You can see the hose come down into the HE from the fan shroud. The air goes through the HE and exits at the diverter valve. With the engine running and the heat OFF you can feel engine fan air coming out of the doughnut-shaped opening....thereby removing LOTS of heat from the HEs.

Posted by: Eric_Shea Mar 21 2017, 06:16 PM

Posted by: JmuRiz Mar 21 2017, 08:06 PM

Excellent, glad you got it fixed!

Posted by: Perry Kiehl Mar 21 2017, 08:23 PM

Always nice to see a problem resolved, especially when it doesn't involve lots of $$.

Posted by: Cairo94507 Mar 21 2017, 10:03 PM

Great work and investigative know-how.

Posted by: gereed75 Mar 21 2017, 11:43 PM

Nice work. Isnt it amazing that Grady's voice still provides so much knowledge

All makes sense. The factory engineers were very good

Posted by: porschetub Mar 22 2017, 01:53 AM

can't for a minute see how this sorted the issue,if the air supply to the HE's wasn't capped of I would say lack of cooling air to cylinders and oil cooler but they were capped !!!.
I run headers with block off covers on both sides of my engine runs great oil temps,this is known to provide better cooling besides.
Have worked with aircooled engines for 30 odd years this one has got me stumped

Posted by: gereed75 Mar 22 2017, 06:45 AM

Tub, the heat exchangers on the stock headers effectively double wall the headers preventing cooling air from carrying heat away from the header and tubes. Then the exterior of the heat exchangers is also heated


I can see where this is a much bigger heated mass and a much bigger heat radiator than just the air flow cooled header tubes. The result would be more heat transferred into the heads

Would like to see an analysis by my thermo dynamics prof but That's my theory

Posted by: Perry Kiehl Mar 22 2017, 07:03 AM

To take gereed75's theory a step further, if the heat exchangers can't allow the hot air to escape it's going to back up the positive air flow. As long as the hot air can get out, either to the cabin or out the vent in the flapper box, there's positive air flow and it won't be a problem.

The reason this isn't a problem in a car with headers is because there's no restriction of the cooling air flow.

Posted by: bretth Mar 22 2017, 07:14 AM

Years ago I rigged an electric fan in the spare wheel well to blow heat through my 68 Bus heat exchangers in an effort to keep from blowing engine fumes into the cabin. I ended up having to run the fan all of the time because the exchangers would get hotter and overheat the flex hoses I was using and cause a burning smell. I can see how this could cause additional heat in your situation.

Posted by: rgalla9146 Mar 22 2017, 07:56 AM

That would be the esteemed Grady Clay of Denver Colorado.
Proud to say I met him long ago.
He left this world in 2014
RIP

Posted by: Justinp71 Mar 22 2017, 11:26 AM

Wow, what a difference. Nice find! Thanks for sharing.

Posted by: porschetub Mar 22 2017, 12:51 PM

So they basically cease being a heatexchanger without the flow from the fanshroud,the heat builds up but has no where to go right ?? so it transfers back into the engine, hot heads = hot oil =high temp right ?.
Thanks for helping my clear this up Perry and gereed75,good I have that in my thick head know .

Posted by: 767driver Mar 22 2017, 01:12 PM

When I pointed my IR thermometer at the backside of the oil cooler near the bottom I got readings near 300 degrees (after driving it) before I put the ducts to the heat exchangers on the car. After I installed the ducts (and driving again) that same area of the oil cooler read 235 degrees!!!!!!! The oil cooler is only a few inches above the exchanger. Imagine how much heat must have been radiating upwards onto the bottom of the cylinders..:-0

Posted by: gereed75 Mar 22 2017, 01:41 PM

That says a lot

Glad you got that worked out. I believe that that is Puffs old car I had faith that it was solid (looks right too!!)

Posted by: 767driver Mar 22 2017, 03:23 PM

It is Puffs old car. He was kind enough to pass along the needed ducts!

Posted by: rudedude Mar 22 2017, 03:40 PM

I can't wait to put this theory to test in mine. It will have to wait a while for weather to improve in my area. I hope it works as I have battled higher temps in my 2.7 than I would like to see.

Posted by: porschetub Mar 23 2017, 08:14 PM

Don't know who puff is lol ,what ever way real nice car ,go out and enjoy