As the title says, if I stomp on the gas, after I let go it does a little backfire. Is that normal? I rebuilt the engine and it nvr did it before.

Also I only have headers on at the moment, could that be why?

 

Backfire is from the intake. Do you mean it's firing in the exhaust?

 

No I'm pretty sure it's the intake. I just thought that maybe having no exhaust is causing it

 

Running open headers is a little risky on your exhaust valves. I hope their are at least long tubes. Shouldn't really run any less than 36" from the exhaust port. It is not normal for you to have a backfire after hard acceleration. Wouldn't expect that even with open exhaust. What ignition are you running? You may have too little advance on low manifold pressure. It's causing you to have reversion through the open intake valves. Same as retarded timing on acceleration will cause backfire. However, try running it with the exhaust connected and see.

 

Yea i know about the short exhaust being bad sometimes. But I ha to make sure it ran good before I got the exhaust put on. And I just realized I forgot the distributor vacuum advance. So I gotta hook that up. Maybe that will help a little

 

You at least need to have the Y-pipe installed to run the engine on short tubes. You will warp exhaust valves. Especially the stock junk. The vacuum advance should help with the backfiring but don't judge the motor on what it does with open headers. It's not set up to run that way.