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

5261 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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Plugs look very decent for a change . rechecked timing and its 20 at idle and 38 at 2800 . Readjusted valves and a couple were loose on passenger side . That didn't fix it but the pop wasn't as loud or as long . Low speed air bleeds is my next thing to try as was suggested to me . don't know nothing about them other then they are 62's in it now
What kind of carb is it? Fat intermediate circuit would be my guess. Does it have a power valve in the front?
i am gonna bump up the fuel pressure also as i noticed it jumpy from 4.5 to 5

Its a BLP carb , but has power valves front and back :wacko:
The setup is at this now on the front . Got a few things iam gonna change tomm as someone suggested via a pm .

squirter is a 31
power valve is 3.5
Jets are 72
low speed bleed jet is 62


Rear is setup like this . ( changing to block off the power valve tomm thou and jet up . )


squirter is 32
power valve is 3.5
Jets are 74
low speed bleed jets are 62 also
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