Cylinder Head Temperatures, Calling on the Brain Trust and they Win! |
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Cylinder Head Temperatures, Calling on the Brain Trust and they Win! |
Mblizzard |
Aug 30 2016, 12:49 PM
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#1
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
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) |
Jake Raby |
Sep 12 2016, 08:59 AM
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#2
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
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. This post has been edited by Jake Raby: Sep 12 2016, 09:05 AM |
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