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I have relayed some of your thoughts already and tomorrow when I bombard the builder I will relay the rest. he said he was tearing into the engine on Wed. so I figured I'd give him a few days to find something then call to get the lowdown. I did call someoone else though and this is very interesting and quite frankly extremely plausable.. let me run this one by you and see what you all think sense you have given me so much good information already. I called the cam people.. comp cams. and spoke with their tech.. I gave him the model number and of course he pulled up all the particulars on the cam.. ( they did build it after all LOL), he asked a few simple questions about the rest of the valve train and what heads I was using and here's what he came up with. A normal engine will produce a drop in pressure accross the carb under very heavy load, pulling a steep hill, maybe towing a heavy load etc and cause the power valve to open dumping extra fuel needed to maintain engine rpm and speed. The particular cam that is in this engine however causes the pressure drop almost immediately upon throttle advance, in other words any time I step on the gas the vaccuum seen is virtually nothing therefore the carb is falsely seeing a severe load demand almost all the time and the power valve is constantly dumping extral fuel, which is not needed caused a over rich condition, fouling the plugs and dumping raw fuel into the exhaust which is then burned ergo, the "backfiring" upon acceleration. Man did that make sense to me when I thought about it. It also explains why it doesn't do it when you just freewheel the engine vs. in gear under driving conditions. It also explains the constant black spark plugs and almost everything else. To correct this all I have to do is simply buy a power valve plug and gasket from holley and replace the reg power valve with it.. The only drawback will be that if I do pull a hill I'll have to push the gas pedal to keep the speed up rather than the engine doing it for me.. BIG DEAL>> does this sound like a feasable reason and solution to you folks.. It certainly did to me. Even if it isn't its a very cheap try so what the heck. I do want to thank you for all your help and information and believe me none of it will go to waste.. I'm still having everything you have mentioned checked out.. no stone unturned leaves room for error.
thanks again and take care all.
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