back fire

[72ScampTramp]

I've done some tuning changes and feel really close. When driving I get a low middle backfire out exhaust. I'm down 2 60 for jets in both carbs. The loud backfire is gone. I'm at 20initial and 36total. Only,does it when I let off throttle and only while,driving not,in park

 

[ddettloff]

I had same problem was a small leak at headers when I backed off cold air would suck in and cause it new gaskets and no problem.

 

[forphorty]

Do you have an exhaust leak? That will cause it.

 

[forphorty]

OOps, treed by ddettloff

 

[72ScampTramp]

Just did new header gaskets last year. Very little run time. Went eith those expensive remflex but that don't mean one can't be loose

 

[RustyRatRod]

Josh if you still don't have tail pipes it could be perfectly normal.

 

[72ScampTramp]

I don't have tail pipes out the back but I've run new back to the wheels and out

 

[AJ/FormS]

Popping in the exhaust is usually caused by unburned fuel entering the pipes and finding sufficient oxygen there to re-ignite.However this often causes multiple pops if it a carb issue. If its just one, its usually exhaust related. Like mentioned. a leaky header flange or even a collector gasket.
But since its happening under decel, a period of high vacuum, and when the cars momentum may be driving the engine against compression,and closed throttle, there shouldnt be enough fuel in there.Unless maybe its pulling it through a bad PV, or a too-far-closed transfer port.
I wouldda thought late timing, but 20 initial sounds really close.
IDK. Im kinda outta my element with 2 X 4s.