I have a '79 F250 with a newly rebuilt 400. The engine has an edelbrock camshaft and timing set, weiand intake, and summit racing headers. Everything else is a stock set up. The other day it started backfiring out of the carb. When i would stop at lights and such it would idle down to about 500 rpm and almost die, when I would try to accelerate from the stop the engine would backfire and nearly die. Also, running at higher rpm when I would open the throttle it would also backfire. If I eased into the gas it wouldn't have as big of a problem. I am set to check the timing in the next little bit. What could be casuing a new engine to do this, and what would also be optimal timing for my set up. Thanks for any help

 

I would also start with timing. Hopefully others will chime in, but I'd say 12-14 degrees timing would be a good start. Let us know what you get with your timing.

 

I agree timing to start, If it's timed right check for weak spark.

 

I was checking my spark plugs and noticed the distributor was loose, I believe this is the problem, when I get it timed i'll share the results, thanks for the help!