for some reason, my car is backfiring out the carb and exhaust intermittently when the vacuum advance hose is connected to the carb. disconnect it and plug off the nib, and it runs just fine. this is regardless of how we set the advance on the distributor.

it's not like explosive backfiring out the exhaust, more of the little headerpipe fart noises you'd hear if you switched two plug wires. we thought it might be the ignition control module not being able to interpret what to do, but can't think of much else that would cause that backfiring out both the carb and the exhaust. any ideas?

could it be a screwed up vac adv. arm or diaphraghm?

how can i tell aside from pulling the cap, and sucking/blowing on the vacuum advance hose?

in due time...

jason

Could be a bad ground or a fried condenser.

hmmm. where's the condensor on an hei distributor? mine (as far as i remember), has the coil internally, the msd unit instead of the stock module, and that's it.

i'll check the ground asap though!

jason

sorry I was thinking of a points ignition.

do you have an adjustable vac. advance, if so take some timing out of it. you're probably advancing to much with the vac.