Backfiring like crazy when deceleration on a slight hill..

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
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Massachusetts
I don't know what could be causing it except having more fuel maybe? I just put in 36# injectors and a 255lph high pressure pump, and now it seems to back fire a little bit more than before I put just the pump in. It was doing it with the injectors alone, but now it's really loud. Is this a bad thing? what is causing it and how can I stop it?

I also have an A-trim pushing 5-6psi, timing set at 10*, 93 Octane, and Autolite 23's @ .035"
 
Have you read the plugs? Is it backfiring through the exhaust or the intake? Are you talking about popping through the exhaust, or real loud backfires, like gunshots? Some popping can be caused by small exhaust leaks, or a short exhaust system. Mine pops some on decelleration, or during a shift, but there is nothing wrong with it. Does it accelerate fine?
 
I have a mac catback, my h-pipe has a hole in the part that connects both tubes together, but I patched it. I don't have any other exhuast leaks other than that.

I can hear a hissing around my intake somewhere after I shut the motor off, but not exactly sure from where. I tried to find it but can't pin point it, aos i have no idea where it's coming from, would a vacuum leak cause this maybe?