Cylinder Head Temperatures, Calling on the Brain Trust and they Win! Options

[Mblizzard]

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.



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? (IMG:style_emoticons/default/headbang.gif)

[era vulgaris]

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.