extreme popping from exhaust pipe

What can be causing a loud pop out the end of my exhaust pipe. It's a Chevy 400. It does it at idle and when I let off the gas after reving it. At idle it does it every 30 sec. or so. Also has alot of condensation out pipes at start up. I forgot to mention it's a Quadrajet. It starts and idles good A little on the fast idle side.

Thanks

Ralph

I'm going to look at that.What about at idle? It's sounds like someone hitting the back of my car with a lead pipe.

I haven't actually checked it but without the occasional pop this motor runs strong

Thanks! I will do that

check the timing...it may be late...or you have a cylinder not firing?....check with a vacuum gauge....reading should be absolutely steady at whatever vacuum....

Check for the dead cylinder...just short them out one at a time with a test light and listen for the rpm drop...the one (or more) that rpm doesn't drop will be the ones to look at ....

hook the test light to a ground and puncture the terminal at the distributor (dis) tower/post and walla....

Does it have a catalytic converter??
I'll bet youv'e got one cylinder not firing all the time, and raw gas going into the Cat,,,then it would pop like that.
Also check out your Vac advance for proper operation,,if it's sticking advanced on idle then your rpm will be outa whack

THANKS!! It was the #8 sparkplug wire burned from the headers.
Thankyou for sending me in the right direction.

Ralph:)