Backfire on decel and cruising, No exhaust leak... what to check next? Options

[Lawrence]

I crawled under my car last night to see why I might have backfire. I figured maybe some piece of exhaust hardware had loosened itself up. Nope, everything looks good.

I'm thinking the issue is carbs, since that's the last thing I played with. What should I check next?

TIA,
Rusty (IMG:style_emoticons/default/smoke.gif)

[si2t3m]

Hi Lawrence,

While this might not be of any help, when i'm WOT, and back off, i get a pretty big backfire. enough to have reports of flames coming out of the tailpipes at the last DE. But this was at the track.

So what is it that you are hearing? Pops in the intake or backfires in the exhaust while cruising?

When you say that you are getting this while crusing, any idea of the rpm rang. Check it under 3000 lets say 2000-2800, then at 3000-3500, then at 3500-4000.

take a look at http://www.inglese.com/tech.htm. this will give you an idea of the magic that is happening in the carbs regarding idle jets, main jets, emulsion tube, air correctors and so.

Are the floats set and double checked, is each cyl in a bank is in sync drawing the same air, aret both banks in sync also (at idle and a 3500rpm), ignition timing is set, fuel pressure is in the 3-4psi rang.

Id go warm up the car to 180 and and reset the idle jets. turn the idle jet in till that cylinder drops (rpm goes down and you can hear that you lost that cylinder) then bump it back up till it catches back. I do this slowly in 1/8 increments. I give it a 1/2 turn out after that cylinder came back and i move on to the other.

HTH

Marc-André