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popping in exhaust ... at low rpms / burnout not when floored

5260 Views 7 Replies 5 Participants Last post by  jbird
So i took the Malibu out and wanted to check a few things before i goto the track . Got it off the trailer and it sounds great . Let it warm up just a little and decided to check the transmission gears . I put it in low and go slow ( like coming down the return lane ) It makes a couple pops in the exhaust . I thought maybe it wasn't warmed up , after a little more warm up same thing.. Does this starting off in 1, 2 or 3rd gear as long as i am not in the throttle hard .
So i decided let me try launching the car ( no burn out ) i foot brake it to 2600 rpm and hold it just briefly and floor it . Car launches hard and does NOT pop or break up , doesn't miss a beat . Shift into second and the car gets loose so i let out of it . At this point i fiqured the pops earlier may have been from not being warmed up enough .

This time i decide to put a little water down and heat the tires and try launching the car . Start the burn out and same pop in the exhaust . I think to myself it just reved to 6800 perfect. So i abort the burn out and stop , Not bringing the rpms very high as i was unsure what just happened . I fiqured let me flash the convertor and launch ... ... perfect , no missing or poping .

I decided to stop again and try pushing against the convertor again and launch ...once again perfect . Decide one last try to do the burn out ... its a no go , started poping ( sounds more from passenger side but it has h pipe on it so its hard to tell and listen to other things ) One last attempt to *act * like its on the return road . Same thing , it pops ( approx 1500 to 1800 rpms ) lightly give it gas and it does it once or twice more , Floor it and it clears up .

What would make this happen ? I was thinking maybe valve lash is not correct but think if the valve lash was not correct it would do this even on the launch . Same with a carb issue .

I really want to go to the track wed . but need to try to get this fixed so any suggestions or advice would be helpfull.

Thanks

James
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What kind of carb is it? Fat intermediate circuit would be my guess. Does it have a power valve in the front?
Still sounds like it is rich part throttle. You didn't say what kind of carb, only who built it. Sounds like the same problem with three circuit Dominators. Too rich part throttle. Usually doesn't happen with a power valve though. Try reving the engine to 1800-2000 rpms while watching the boosters (in park). If the boosters start dripping fuel in that rpm range, that is likely the problem. Lower float settings may help. Call Bo Laws and ask their opinion as well.
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