drnerve

I,ve got a pretty stock L48. It has headers and Mid Americas chambered exhaust. I just had a Mallory Unilite HEI distributor put on. When I let of the pedal, the exhasts has sublte puffs or pops. After WOT, and let let off the accelerator, it will pop loud, and even back fire. Is this because the timing os off? Thanks for the input. Pat :confused:

tnt76vette

I think I would retard the timing just a bit and see if that cures it. :yesnod:

Fevre

Believe the chambered exhaust does that but you might be running lean with new headers. Do you have any exhaust leaks? Those will also cause popping and back fire.

drnerve

The headers have been on for years, but there are no leaks around them. When I was reallly into it on the freeway, and let off the gas suddenly, it would crack. It didn't do this before the HEI and the mechanic adjusted the fuel flow, it was running way too rich.

Jack71

I think that has something to do with unburnt fuel igniting in your exhaust system as your motor whines down with no load.

munday

:withstupid:

extra unburnt fuel igniting in the exhaust (combusting due to heat)

If uncle buck can do it, so can you!!!!!!

standup

the pops shouldn't be an issue.....but the backfiring....how bad is it??? Would it blow a cat off the fence???? If so, since you've change the distributor, then I agree you should look at the timing.....

greatgonzoglenn

I had the same problem with my Z-28. I would have to agree with the header gaskets. If they have been in there for years, they could be very brittle and breaking. Mine split and cracked all over the place and when replaced, purred like a kitten. :flag

drnerve

Thanks for the replies. I think it wouldn't be sa bad idea to replace the header gaskets anyway. Thanks Pat :cheers:

ddecart

Idle mixture screws too far in and the butterflys too far open at idle will do it. Drawing on fuel/air from the main circuit and not fromt he idle circuit, so when you cut the throttle there's excess fuel being drawn in through the main circuit.

Is it really rich at idle?

drnerve

It was burning very rich. If you revved the car, it would leave a lot of carbon on the ground. The mechanic said he got the richness out. It didn't sound like this when it was burning really rich. This morning I had it out. It does not idle well when cold. Before I got it up to 190F, it was about 170F, I was accel up hill and it popped, not real loud, a few times. Also after it was fully warm, it wouldn't run well at low RPM's. It seemed like it wanted to die, and it did once. I paid a lot to this mechanic, its going back to him tomorrow. Pat :banghead:

OHSIXX

Mine pops on deaceleration as well.. Is this a biggy? :confused:

norvalwilhelm

Idle mixture screws too far in and the butterflys too far open at idle will do it. Drawing on fuel/air from the main circuit and not fromt he idle circuit, so when you cut the throttle there's excess fuel being drawn in through the main circuit.
Is it really rich at idle?

I agree with ddecart. In stock cars you see the flames and back fireing on the corners and this is caused by improper idle adjustment. Fuel is beeing pulled from the transfer slots and igniting in the exhaust.

Diode

Mine backfires like crazy just because of C3 chambered side pipes.

ddecart

But it sounds COOL! :thumbs: :D