OK so I have reviewed the information by Jake regarding cylinder head temperatures http://www.914world.com/specs/JakeRabyHeadTemps.php.

A bit of background.
Engine 2056 based on 74 2.0 engine # GA 014782, stock cam, stock FI, fuel pressure at 31 psi, recently added big valve heads, external oil cooler, valves adjusted correctly with engine install, 150+ compression on all cylinders, stock Trans, Evo Muffler, all stock cooling items in place (flaps and tins), running 123 electronic distributor set to the curve for the 0 231 174 011 dizzy which is correct for the 74.

Timing seems to be correct using the marks as indicated in the photo below. Likely at about 25 BTDC.

Click to view attachment

At cruise I see temps in the 350-375F range with it being pushed to the higher end and above. On hill climbs it will go quickly to the 400F range and run at that for the duration of the climb. Most I have seen is about 405F. Letting off the throttle quickly brings the temp back down so I have to think the cooling system is working.

I would expect a 2056 to run some warmer but not to be consistently in the upper end of the range I am not sure what is causing this. I have seen lower temps on cruise by richening up the mixture. But overall based on the guidance it seems to be running too hot.

I have suspicion my AF meter is reading too rich so that might be part of it showing an acceptable AF range but could be going lean under load. Changing out the sensor and will recheck.


So given all of that what do I check or where do I start changing things to bring the temps down? Taking a few degrees out of the timing helped but not significantly.

Anyone?

How about:

Engine tin in place correctly and holes generally plugged?
Engine bay seals in place?
Do you have the heating components/air guides in place?

I notice that my head temps, or the readings, seem to go up significantly when I have the heater on. No good idea why. I ended up capping the J-Tubes in the engine bay to try to keep heat from the exchangers from bleeding into the engine bay.

Only other suggestion is to really inspect your cooling flaps to make sure they are in fact moving all the way. I think sometimes that spring will be "sticky..."

Try again with the timing advanced 2-3 degrees further.

Chris because this has me stumped I have to ask to make sure that I am not thinking about it incorrectly. I was operating under the assumption that advancing the timing beyond the 27 would add heat?

What is your AFR?
What is your cruising rpm?

With my 2270 I cruise in the mid 12's AFR. My head temps are in the 315-325 range for cruising in 4th gear between 3k and 4k rpm. Lower gears will see even less temp as there's less load on the engine from wind resistance.

Beatnavy, my head temp gauge also reads a few degrees higher with the heat or the headlights on. The temps aren't actually higher though- it's an electrical anomaly with the digital head temp gauge not liking the voltage drop that such a large electrical load causes on our 40+ year old electrical systems. I reduced the amount of error significantly by cleaning every electrical contact I could find.

The AF readings are suspect but in the high 12's sometimes going to 13.

Typically running at highway speeds 70+ MPH at about 3K to 3.5K.

Slower speeds drops into 350F range.

On the interstate it is going to be higher due to the increased wind resistance, and even higher still if you've got the top off (even more wind resistance). I'm around 335-345 on the interstate in 5th gear on a flat grade. Taking the top off will increase that by 5-10 degrees on the interstate, about 5 degrees in 4th gear speeds, and negligible if any difference at all in lower gears.

What AFR gauge are you running?
If it's working at all, then you probably don't need to replace the sensor. It probably just needs to be re-calibrated. With mine (Innovate MTX-L) you unscrew the sensor from the bung in the exhaust and leave it in open air, turn the ignition to 'on' for like 30 seconds IIRC and it recalibrates itself. If you have the manual for it it'll tell you what to do.

In my experience, advanced timing raises head temp. Retarded timing raises oil temp. Stock gauge measures oil temp.

AEM gauge. No calibration. The instructions state high temp and rich conditions could degrade performance and response. I had both of those so it is something to check.

I am usually topless! TMI I know.

Don't assume. Verify. Your engine combo isn't the same as stock for one thing. You really don't know where the sweet spot is for combustion efficiency.

Also, is your MPS full load stop screw adjustable? If it is, try backing it out half a turn and see if that makes any difference.

Compression ratio info? What is it?

Did I miss something here?

Nothing high. Standard flat top Pistons from AA.

You are so right! I will verify.

MPS is adjustable thanks to your kit. Will back out the full stop a bit after answering the timing question.

Update: Well a couple of discoveries. First CHECK FOR VACUUM LEAKS! Looks, like I had a leak on the runner seal going into the plenum. Guess which cylinder? Yep number 3. Have to think it was causing that cylinder to run lean.

O2 sensor was reading way rich. Replaced with nice Bosch unit. Seems to be much more in line with the way you would expect it to read. Got a little more fuel going in now.

And took Chris's advice and bumped the timing back up.

Drove the same circuit and temps were some 20 F cooler. Still pushed 389 on hill climbs but cruised at about 360 to 380.

May still have a few adjustments to make but much closer to expectations.

The thing about temps that has to be kept in mind is that T4 heads (and most aircooled engines) are for more susceptible to damage from high EGT's than CHT's.

And tuning parameters that cool the chamber in the spark plug area (the proper place to read CHT's) often have an inverse impact to EGT's.

A slightly fat mixture with slightly retarded timing will generally yield lower CHT's but may very well yield higher EGT's. Here's why:

When retarding timing from the optimum setting (whatever that may be for the combo on hand) there is less time (chrono time, and crank degree time) for the mixture to burn in the chamber, so some of it will react in the exhaust port, or near the exhaust valve.

Fattening the mixture will, as a general rule, require more time to burn (more fuel, more chrono time. More chrono time requires more crank degree time for a given rpm).

Up to a certain point, what doesn't react in the chambers will react in the exhaust port/system. Too rich and/or too retarded and you may actually blow raw fuel out the end of the exhaust system.

Tuning parameters that are far removed in either direction of optimum can give increases in both CHT's and EGT's.

Highly elevated EGT's can heat the entire head enough to raise CHT's too.

Due to the design of T4 heads ex port area, which cuts directly beneath the combustion chamber, high EGT's can quickly lead to warpage and head leaks.[i]

It is amazing how I find that the more I read the information posted on the world it becomes more appeant how much I have to learn .

Wish I had the time to get some of your heads for this swap.

OK so I am still struggling with this. I have been playing with timing and fuel and can seem to really bring the temp down to the ideal range. Normal city driving the temps typically remain in the 375 range. But once I get on the highway at about 70 the temps steadily climb and hover at the 380 range and go to 400 on any hill climb.

Changed the plugs and checked the gap at 0.28. I have tried multiple advance settings from the 009 to the stock settings.

I am at a loss at what to do next. I guess I will go back and check the dizzy to be sure it is working off TDC and that all the timing is correct. Checked timing with multiple timing guns. I guess that the only thing I can try next is to really richer it up to see what happens. But as HAM pointed out that has a down side as well.

Looking for any and all suggestions on what to look for next.

Mike, do you have a wide band AFM set up?


Crap, ok, i see you do...

Yep,sure do.

When I first bought my car I was in the exact same boat as you as far as head temps. Typically running in the high 300's and approaching and hitting 400 on the highway.

A couple things that helped me...
Now I have carbs and you obviously have FI, but this might give you some ideas at things to look at.

The PO of my car had a phenolic gasket on the 1/2 side and a pair of paper gaskets sandwiched together on the 3/4 side. I think the 3/4 side had a bit of a vacuum leak. To compensate for this, he had put in massive idle jets rather than fix the vacuum leak. Why anyone would do any of these things, I don't know! But it was one part of my problem.

The other part of my problem was that the carbs were horribly synched. Having the 4 channel gauge, I could see in real time the effects that carb synch had on all 4 of my head temps while tuning. Even drifting slightly out of synch would raise my head temps drastically on the side of the engine where the throttle plates were more open. So basically, the more open the throttle plates (or the more air that was getting in), the higher the head temps. I don't even need to use a unisyn to sync them anymore, I use the head temp gauge!

Once I replaced the intake gaskets with phenolic on both sides, and properly tuned and synched the carbs, my head temps came down to where they are now.

It's possible that you have a very slight vacuum leak somewhere, or that some aspect of your FI system is not allowing a perfect balance in tune between the left and right cylinder banks.

Wrt the comments above,
try moving the CHT to another cylinder to see if the high temp is isolated or across the board.

If you try Chris' suggestion to test a different cylinder temp, here is a bit of reference point as far as temps across the cylinders...

#'s 1 and 4 are within a couple degrees of each other. #2 is about 20-30 degrees below 1 and 4. And #3 is about 20-30 degrees above 1 and 4.

So for example:

1) 300
2) 275
3) 325
4) 300

I'll look next time I drive on what the exact numbers/relation between cylinders are on my car, but that's sort of a general ballpark for you to work from.

I was going to do that this weekend! Will post the information.

I would rethink timing???
I dont know about 2.0 but cant your timing be checked at like 3000RPM or something like that,to see what advance your running.

My 1.8L ran hot all the time,seems the Porche shop that worked on it,does not know how to set timing on a 914.

After I adjusted the timing,and valves my motor is so quiet.
And no longer runs hot.

At the bottom of the timing adjustment article,a guy tells how to manually check timing.Might be worth trying.
http://www.pelicanparts.com/techarticles/9.../914_timing.htm.

This year's summer blend fuel has changed... I have seen all engines be harder to start when hot, and with the same tuning as last year everything is running hotter... A couple of my personal cars are a good bit hotter, and I have had to throw some changes at the timing and enrichment that have never been needed with these cars before.

Back the timing down 2 degrees and see how i responds.

We have to constantly watch for changes to things like fuel, no one tells us when something changes. I know what settings are supposed to work with the combos, and when a mass of them no longer do, then we know to look elsewhere.

Nothing ever stays the same, the way these engines tune today is wildly different than 2+ years ago.

interesting, since ive had to run different octane fuel in my truck to eliminate an issue that came up this spring/early summer - this might explain why- and alson in my 2.0 914 stock d-jet car I had been running 87 no ethanol, but 89 might be a bit better if the fuel blend is different? also back the timing down 2(meaning 26 rather than 28 at 3400rpm?)

I have backed it out to about 25 but still running hot. Will back out a bit more tonight and test.

I have all of the dizzy options to select
I am thinking about going back to my stock Dizzy instead of the 123 electronic to see if that is an issue. I think the 123 batch fires the injectors instead of firing them in 2 at a time.

On the 123 dizzy I have all of the following options. Currently running the 011.

From looking at these it seems that the advance is all in at about 2700 rpm.

Click to view attachment

But this seems to correlate with the stock settings from Bosch. Note that you have to double the readings on the graph below.

Click to view attachment

But I have to think that because it seems to only heat up excessively on highway and hills that it must have too much advance at highway speeds.

If I am thinking about this correctly I think I will have to reduce the total advance back to a level that produces acceptable head temp on highway and depend on the 12 degrees of vac advance to get some low RPM performance.

None of the other setting for the 914 seemed to make a difference in temps.

If it still runs hot with a couple degrees of retard, then try advancing to 30* and see what happens. You can have high CHT associated with high EGT, elevated by retarded timing that doesn't match the engine combo/ fuel/ enrichment.

I'd go to 30* then 32* and watch it closely. This will rule out any chances that the engine wants higher ignition timing.

If the engine responds the same you have to start thinking about enrichment, and even a misconfigured engine combination, or exhaust issue.

Of course missing engine tins, and etc go without saying... And of course remove and clean the cooling fan... That alone can make a 20 degree difference in CHT.

What oil temp are you seeing? Its easier to tune an engine if you can balance both the OT and CHT simultaneously, and often times the OT will give us hints as to what needs to be done with the tuning spectrum to reach an acceptable result faster.

Make sure the 123 isn't running wasted spark, if so your timing light will do no good... It'll show twice the ignition pulse that it should, so you'll actually be running 1/2 the timing that you think that you are.. Been there, done that.

Thanks Jake.

I went a little forward on the time but not as far as 30. Will do that tonight and see what happens.

Engine was recently out and I cleaned everything and verified all tins were in place.

Because I had apparently overheated and crack both heads previously I paid special attention to the internal flaps to be sure that they operated correctly.

Oil Temps seems to run a bit high but on 90+ degree days only see the "M" on the gauge as a high. that is with an external oil cooler.

Running a CFR Evo exhaust and stainless heat exchangers. While not high flow I would not think it would be restrictive.

the 123 does not seem to run a wasted spark approach but I am checking to be sure.

You need an oil temp gauge with numerical values.. I don't trust the stock gauge for anything.

Just put a 123 on this car...

Click to view attachment

Has me wondering. I'm going to take the injectors in tomorrow am for testing. No intake leaks were present.

Timing was too high... Guaranteed.

Can't say that's an engine mod I am looking for. The slow incremental approach seems valid!

I have new injectors but how would faulty injectors cause that?

Lean condition.

It's just on #3

Set at 27...

I'm hoping that dizzy isn't the culprit.

If the timing was too high it'll look like the engine was lean, and it always happens on #3 first.

The high timing burns too much of the fuel mix, and looks like its lean. I've chased my tail because of that before.

Well it may be premature to do the happy dance but thanks to the guidance from Jake and Eric, I advanced the timing to about 30 degrees. On a short drive ran much cooler. 375 or less most of the time only approached 390 on hill climb that had previously pushed it to 400!

Oh and it seems to have a lot more power!

I think there is a bit more advance to add but after Eric's photo I wanted to be careful. AF never indicated lean conditions so I feel pretty good that it is not running too lean.

Will drive it in the heat of the day tomorrow and see if there are any changes.

If it runs hot in the sunlight I'd sure put a different distributor in and run a baseline

That tells me that someone set the compression ratio a little low.. Since it ran cooler at 30*, now try 32*. Find a stretch of road up a hill and hold wide open to the top, do this over and over with different timing settings and advance until temps go up, you hear audible pinging, or the car feels slower.

This is how I developed engine combos and tuning for them before I had a dyno. Doing this will tell you everything about the engine.

Not sure if the compression was ever "set" I think it is just a combination of parts that was hoped to work together.

I have not hear a single ping yet. So I think 32 may be the answer.

Will try the 32 tonight. Drove to work this morning over about 20 miles and all was good. Will do the run again during the heat of the day to see if that makes any difference.

Compression was set, it may just have fallen wherever the components lead it to.

Sad.

Got confusing set of data on drive home. Car ran hotter than normal and cylinder head temps were back up. Discovered the electrical connection to the oil cooler had come off and no air was going across cooler.

I am planning to set timing to 32 n try it again.

But I am concerned as to how quickly the oil temp rose with only the stock oil cooler providing cooling.

I have reviewed and checked the cooling system tins and flaps and cant find anything that seems out of place. But it seems clear that the stock cooler is not providing sufficient cooling.

You may have more than one problem causing these temp issues.

Insufficient piston to cylinder clearance will cause oil temps to rise very rapidly.

Jugs that aren't normal to the crank axis due to case warpage can cause this issue too. Same effect as insufficient piston clearance.

Were these things checked carefully prior to assembly?

This engine was dome by Original customs. Essentially a new top end (taken to a 2056) to a good running bottom half. I am sure Mark checked the pistons and such before assembling the top half using the new AA 96 mm cylinders.

This engine has always seemed to run hotter than expected but the external oil cooler seemed to address the oil temps. When running on a 95 F day with the external oil cooler fan running, the temp will go up to the upper end of the M on the gauge but never towards overheating or pinging.

But I have always thought I hear an odd sound in the engine at times like a knock but no one else has ever been able to hear it. Could be a problem in the bottom?

My level of expertize in the recent head replacement was essentially to swap them out and make sure I had no parts left over.

AA's are noticeably noisier than the KB's in Jimmy's engine. Haven't seen any reliability issues with them, just noisier.

Speaking of KB's; report from the injector shop came back just now. #3 down in volume and spraying a straight stream. It appears that's what holed Jimmy's KB.

So...you recently swapped out the heads? Did you set the deck height?

I hoped that it was done previously. I checked the recess on the new heads and it was reasonably close to what the previous heads were. I do not recall the exact measurements but there was actually a but less depth so if anything the deck height is higher and the compression is a bit lower.

But the temp problem predated the replacement of the heads. I replaced heads that were heat cracked so I don't think the new heads are the issue.

Ok so I think I have done it all. But I was looking through the FI Trouble shooting guide and ran across this in regard to poor output excessive fuel consumption.

Defect is usually accompanied by excessive noise (droning, grinding etc.) and/or by
excessive heat development.

I did the rebuild a few years back with the DR. but I have always head a noise in the trans. I am starting to think that because this only happens at highway speeds that this could be a possibility.

Anyone got a spare good, side shift trans that they can help me before Okteenerfest prior to Wed?