FUELforTHOUGHT
by Dave Koehler
11/8/06
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Eddie,
Looks like you have some nice parts to work with. At least the unmelted ones. Unfortunately new pistons won't make a base tuning issue go away. I am surprised that no one suggested you find the cause of the damage before going out again. Since detonation has been diagnosed as the culprit and nitrous is not involved we will concentrate on that.
While you didn't mention compression ratio I assume, based on the other parts listed, that the engine is high compressioned and if so I will also assume that you are running the appropriate racing fuel as a result.
Essentially, burning and blowing holes in pistons is caused by a lack of the proper volume of fuel, too much ignition advance or both. A possible massive air leak from the manifold due to a bad fit or under the carb could also contribute but it is not common. The air leak is usually diagnosed by an uncontrollable high idle rpm and a necessity to run a really rich setting on the idle circuits of the carb. Check it out anyway.
You also need to check that the TDC (zero) mark on the harmonic balancer and number 1 piston at TDC agree. I have seen more than one outer ring slip on a rubber lined harmonic balancer. This includes brand new cheap aftermarket versions. Do not depend on a bolt on pointer as being correct either. You may have more advance dialed in than you think. Since it is apart, now would be a good time to verify this. I am assuming that you bring the rpm up to find out what your full advance really is. Perhaps re-curving of the distributor is in order. If you are running a crank trigger wheel make sure your distributor rotor and the trigger pickup are in sync.
After getting all that pinned down the next step is looking at the fuel system. Is there enough verifiable fuel pressure and volume available? Are the carb floats set correctly? As to any other carb issues I would send it to a specialist for inspection and/or get the engine hooked up to a wide band meter to see what is going on with your air/fuel mixture. Perhaps a trip to the local chassis dyno guru would shed some light on these issues. Ask around and find someone who has drag strip tuning and diagnostic skills to go along with the dyno hardware.
Now.....If nitrous was involved at anytime in those 9 runs then all bets are off and we have to start over. Even if it was you still need to get all of the above worked out first before flipping the switch.
I hope this gives you some things to look into. Let us know what you find.
Have a safe race,
Dave Koehler
www.koehlerinjection.com
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