FUELforTHOUGHT

by Dave Koehler
7/9/04

Hi Dave, My name is Tim and I'm in Virginia. I'm so glad I found your tech site; I think it's great! I have a few questions, if you don't mind me asking. I have a dragster that I have just started bracket racing at the local 1/8 mile track. I run a 598 bb Chevy with an Enderle tunnel ram (dart intake). I'm having a problem with a constant oil leak somewhere on this engine (I fix one and then another one starts). I built this engine new and have always run this injection setup on it. I've noticed alcohol in the oil (which I know is normal). I always change it after every weekend at the track. Well, this weekend I changed it, went to the track and after 1 1/8 mile pass, oil was running out of the side rails of the pan. There was a fellow there that also ran an Enderle alcohol setup and said that the motor was too fat. So I came home and drained and measured the oil level and there was approx. two quarts more than what I had started with. I ran a 90 bypass pill and 32 nozzles .80a pump. While at the track I changed the bypass to a 100.

Tim, I will try to break this down. Two quarts is probably not excessive and I am glad you don't mind changing oil. I suspect most of the alky in the oil comes during the warm-up and idle phases and not actually during the run.
The leaking seals can only come from too much crankcase pressure. Large
cubic inch engines are notorious for this, even with good ring seal and a good working tune up. You will need to reevaluate your breathing system. Somewhere it has become a cork. A simple vac-u-pan system will not cut it. This may require using an outside puke tank with the breathers attached or using one of the vacuum pump systems.
You state that the 750 degrees is after the run. If this is true this would be an average temp for the idle phase which makes sense. They cool down quick. While egt temps can be all over the map, from engine to engine, you should be seeing much higher temps going down the track. 1150 to 1250 degrees is the most oft quoted "magic" number, but don't hold your breath trying to achieve a particular number. When you see some heat (color change) in the plug strap and the first two or three threads you are close. Then see what your temp is going down the track.
Your leaner main jet change made no difference in e.t. anywhere on the track? This would indicate that perhaps the two jets are too close together in their flow rate. Try a .115 diameter main. You should get an e.t. difference, either faster or slower. Generally you should try richer first. When that fails go leaner. If the engine is dying when you lift off the throttle you may have an issue with the tank or tank capacity and the incoming line. The fuel could be running away from the pump on deceleration.

Have a safe race,

Dave Koehler
www.koehlerinjection.com

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