this is my set up
chevy 4.3L
impco 425, model e and elec lock off
MSD 6AL ignition
HEI distributor

i'm getting a backfire/ pop through the exhaust. sometimes when i'm trying to start the engine it will back fire really loud, everyonce and a while at idle it will pop and when in drive it pops pretty constantly, sometimes killing the engine.

i've messed with the idle mix adj. but it doesn't seem to help any.

any ideas? timing?

thanks,
chris

sounds like a timing issue to me

i've had people suggest:
timing
ground issue with HEI
too rich
spark plugs

nobody seems for sure, i'm gonna try one thing at a time and see if i can narrow it down.

i am running autolite AR133.... coldest plug with good performance

Phi564 I had damn near the same problem with my 4.3 on 'pane and it was that the previous owner installed the dizzy however the hell they thought was ok...anyway got the firing order spot and and she fired right up and runs like a top!!

Dane

figured out that my harmonic balancer had two marks. so what we thought was top dead center on #1 was wrong. adjusted the valves a little and got the timing right and oh yeah, you have to make sure that the #2 and #4 spark plug wires aren't swapped, that will make a HUGE difference. yeah dumb ass i know..............

regardless it runs like a scalded dog now!

Hmm. Always....Never.... GOOD JOB!

Good shit, glad all worked out for you, sometimes its the little things that will bite you in the ass!!

Dane