Hi,i i have been chasing a backfire (after fire) on decel for along time, My friend got a new machine that fills the exhaust up with smoke so you can find the leaks, I was able to fix them all except for the passenger side header right where the 4 pipes come together it seems to be leaking a little there. Not a lot but it is leaking will that cause the popping? and I guess I will have to take it off and try to weld it there? any ideas/options? thanks

 

btt

 

My understanding is that a backfire in the exhaust is from to rich of a air/fuel mixture. I doubt if the leak you are talking about is causing the problem. I would look elsewhere.

 

Not sure if that would cause a backfire, but it should still be fixed. Exhaust leaks can possibly throw off the 02 sensor, but in your case the leak is on the pass side where there is no 02 sensor so its probably no big deal. Can you smell fumes? It will need to come off to be inspected, probably end up needing some welding to fix it.

 

Yes it will. if your running a little rich. I bought a set of Doug's hedders for my duster and they were a two piece set that would plumb around the tortion bar on the front end and didn't fit very snug where the flanged end went over the smaller tube. This resulted in a backfire sound every time I down-shifted on deceleration. Don't ask me why, but I called Doug's in LA and complained. They sent me a new set (free of charge) that fit snug and the problem went away.
I also had a new dual turbo muff system installed on a 74-350 Nova from the stock manifolds back and had the same problem.
After driving it home about 30 mi. and heating it up pretty good, I got under it and tightened all the clamps up real tight and wala!
problem fixed! Find a good welder, tell him your problem and challenge his skill so he'll do a good job, and your backfire should go away!

 

From my understanding a exhaust leak is the number 1 reason for a back fire(afterfire).

 

friend's mustang with a 5.0 has a crack in his h pipe and it backfires in the upper rpm band when you let off and shift.