backfire around 2k rpm

[point45]

First post here, mostly just search and read but i cant find any solutions to this.

Ive got a 318 that i installed a holley 80457 on. Its backfiring between 1500 and 2000rpm but only under load. The engine will free rev just fine.

Also it significantly reduces the backfire to where it may not even occur if i very slowly accel through that rpm range.

Also the adapter plate thats on the engine has restrictions in the openings for the mains, is this the right one?

[MEK-Dangerfield]

Welcome aboard here.   

Is it backfiring thru the carb, or exhaust pipe? If thru the carb, you might be running too lean.

[point45]

thanks for the welcome.

its popping through the exhaust.

[Chryco Psycho]

probably over advancing at that RPM , you could install a heavier advance spring in the dist or retard the timing

[swede-cuda]

 :wave:hej.what restrictions are you talking about? do you have a thermoquad with an adapter to fit a 4bbl intake?as in a conical/tapered adapter.

[point45]

maybe its just the angle im looking at, but it looks like a 4 barrel spread bore to square bore adapter, but the holes for the mains, just look too small for what i remember on other cars.

ill have to wait till the weekend to mess with the timing and look for some heavier springs.

thanks for all the help so far.

[point45]

its not the timing at all, the number 1 and 3 cylinders were swapped at the distributor.

Engine runs great now.

One down 999 items left to fix.

[MEK-Dangerfield]

We got progress.