Re: What causes Cylinder Head carbon deposits

Guys, thanks for all the possibilities/suggestions...

> Let me respond to a few of the thoughts: > 1. Doing the aluminum heads because LT1 with Iron heads is only rated > 260hp, where as the Aluminum heads in the Trans Am/Vette are closer to > 320/330. > 2. I do have a 180 degree thermostat, but that's always been there, I > didn't change it as part of the head swap. > 3. Only run 87 octane gas, as there is no pinging, no need to run > anything else. > 4. Trips are mostly long 30 mins to and from work, mostly highway > 60mph+ > 5. Prior to the head swap there was no burning of oil. > > As far as the PCM tuning goes, should I tell the guy to tune any > particular area?? Fuel/Air curves for example?? > > Thanks

So you only swapped the heads? WHY? Without the cam and related hardware you haven't gained any HP and probably lost some. Thermostat won't make a bit of difference, its only function is to open when it hits it's rated temp, it DOES NOT control overall engine temperature, that is a function of the size of the system. The aluminum heads allow you to run lower grade fuel since they lower combustion chamber temps by passing the heat through to the coolant faster than the iron heads. Because of that any unburned fuel will stay in the cylinder longer and cause carbon build up. The only way to stop it is to get the rest of the parts for the Vette engine and put them in, then swap the chip for a Vette chip and any other hardware that is different. The head is designed for those parts.

Reply to
Steve W.
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Your carbon problem may be directly related to the 180 deg stat. Don't forget the 180 deg is the temp at which the stat is fully open - it will begin to open 10-15 deg lower temp meaning your engine may actually be running in the high

160's much of the time. The PCM uses the ECT info as part of it's fuel/air mixture calibration. The PCM starts out with the fuel curve enriched when the engine is started cold and leans the mix as the engine warms. If it never "sees" a warm engine, it may run rich resulting in carbon during normal driving which you describe. The fact that you hear or have no ping on 87 octane fuel is likely because of this enrichment required by the reduced engine operating temperature. Since the aluminum heads have a reduced propensity to detonate anyways, I would suggest going to the OEM temp stat. You should be able to see the fuel curve if you have a way of minitoring the input/output of the ECM.

You may want the tuner to lean the fuel curve a bit to reduce carbon buildup or, maybe try compensating with timing settings to get a bit better fuel combustion. Again, I would try the OEM temp stat before changing the settings unless you are into fulltime performance. If it is a weekend warrior, you may want to just use the stock setup and, re-program or swap chips for weekend duty.

Reply to
lugnut

Steve,

what "related hardware" are you refering to? The intake manifold was also changed. My 0-60 times have dropped by .5 to .75 of a second, so I clearly have more hp now. The cam from the vette would not work in my car. (IMPALA SS) it would have caused a drop in torque, i need every ft/lb to get that big beast rolling. A more agressive cam would have most likely resulted in a FAILED emmissions test here in Pennyslvania, so I kept the stock cam.

I'm not looking to make the car any faster right now, just looking on some ideas as to where the carbon build up was coming.

Thanks

Reply to
Jim

Faster 0-60 means you have a bit more torque NOT HP. Torque = Acceleration, HP = Top Speed. That is because the aluminum heads allow the computer to increase timing advance due to the heads running cooler and lowering the possibility of Pre-ignition (ping) The carbon is being caused by the heads transferring the heat away faster combined with the cam you are using.

Related hardware = Computer or chip for that engine, Cam, Intake, different pistons. Those are all different.

Reply to
Steve W.

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