Like the title says, I'm currently tooling around with open headers (no money for the exhaust till next week) and I noticed when downshifting or even letting the engine wind down with the tranny engaged it tends to ring out gunshots from the headers.

Is this a problem that will go away with adequate backpressure (I.E. proper piping) or is this the result of poor timing/carb tuning? Thanks in advance. J.

P.S. from what I can tell the backfire isn't coming from the carb. No burning on the base plate since I ditched the leaking holley.

 

Your afterfire maybe a lean condition at high rpms, change one thing and it mostly will affect another.
It's tuning but, not bad tuning, it's just that it was tuned, or designed to run with an exhaust. So, tune it for a free flowing exhaust, or add the piping.

You might try a high volume fuel pump and regulate it down to the required psi if you're going to be tooling around with open headers.

 

Good deal, thanks for the info. I'll be piping it up soon, just wanted to make sure it wasn't anything potentially damaging.