Backfiring on deceleration

[w-lewis]

When letting off the gas, decelerating, my 351W backfires through left exhaust only. More of a popping sound and not really annoying, but just concerned I might be damaging something in the engine. Any suggestions as to how to stop it?

[patrickt]

That's almost always an air leak around the collecter/primary pipes/etc. use the Acousti-Seal that is giving fits in this current thread: Removing side pipes

[w-lewis]

Thanks Patrick

[MOTORHEAD]

Ck for exhaust gasket leak or intake leak also. l

[w-lewis]

I've tightened all of the accessible exhaust manifold bolts, but unfortunately, most are very difficult to get to, even from the underside when on a lift. At this time, the issue is not bad enough to start removing manifold to check for intake leaks. At this point, I think I'll try the header to side pipe joint first.

[Texasdoc]

Sometimes it is a lean condition. Easy to check and it is reversible. Try richening up the idle mixture just a touch. If it is a standard Holley style carb, turn all (2 or 4) idle screws counter clockwise by 1/8 of a turn. If that doesn't fix the popping on decel, put them back where they were and work on the pipes.