Misfiring popping 392

1st Gen 392 / 2 - 500cfm Edelbrock(electric choke) / MSD ready run dist. / MSD Blaster 2 coil. I have replaced distrubutor cap, rotor, wires, coil, plugs. No change. Car starts fine, idles fine, but popping under light acceleration. ANY SUGGESTIONS?

Jack

Have you checked the timing?

A fresh build, or an original untouched motor?
What have you done or checked, other then replacing tune up parts?
Not much info. We will be guessing for months! Gene

A wiped lobe will cause one to pop like that. Sounds like you have gone through the possible ignition culprits. As has been said, a little more information would help.

Put it on a scope and save lots of money over shotgunned parts.

Probably 50000 miles. Running great when parked, about 2 days later this issue raised its ugly head. Tune up parts only. I have not checked timing, plan on getting to that tomorrow (Monday). Did adjust air fuel mixture, no help. Considering new distributor, but hoping the timing will help. Do not remember checking timing, ever. Replaced plugs and wires several times, just never checked/adjusted the timing...

Pull the plugs and do a compression test. That may give you an idea if any one cylinder shows a problem. Is this a problem when the motor is cold, or is it always there? Gene

Pull the plugs and do a compression test. That may give you an idea if any one cylinder shows a problem. Is this a problem when the motor is cold, or is it always there? Gene [/quote

Always. I forgot to mention, when I checked the plugs, they were smooted black and badly fouled. I replace the cap, rotor, and plugs. Started the engine, ran few minutes, still miss firing/popping. Checked plugs again, they were smooted and badly fouled just that quick?

Does that "Always" mean you ran a compression test? What are the numbers? Plugs fouling that quickly can mean 2 things, lots of oil in the combustion chambers, or lots of gas in the combustion chambers. That much gas should give to a pretty strong gas smell, dies it smell like gas when you pull the plugs out? if it does, maybe one of your carbs is flooding the intake, could be a bad float, or something in the needle and seat.

We are still guessing. Gene

Me too Gene. Have not done a compression check. For some reason (maybe because I'm on old rookie, not a seasoned mechanic), it never crossed my mind. I will see if I can get a loaner compression gauge from O'Reilly's? Had some friends (2 are seasoned mechanics) diagnosed, 98%, sure is distributor. After that, we drank some beers and swapped some lies. Ordered new distributor from Hot Heads. Gonna get the friends together again Thursday night to replace distributor, then drink some more cold beers and swap more lies Will get the real mechanic to bring compression gauge from his shop. Keep checking in, will continue to update as things happen.

Thanks,
Jack

New MSD ready to run distributor from Hot Heads. Mechanic came to my house last night, we installed, running as it should. GotterDone. Thanks to everyone for their input and help. All are great bunch of guys.

glad to hear your problem is solved.
any idea what was wrong with the old distributor ?

Id bet the old dizzy had an issue when the vac plate started to rotate.

Appears shorted out due to problem with cap?

carbon tracking inside the cap possibly, or a cracked cap ?
was this an old cap ?

I wish you the best of luck.

My mind isn't following how a messed up distributor will cause the quick plug fouling you described earlier unless the misfire you described was actually a barely running motor. There is a pretty big difference between a misfire and a motor you can barely keep running.

Inaccurate information ends up with inaccurate advice. Gene

Yes. Probably 10 years old.

Car started great, idled great, ran great, but would skip and back fire under acceleration.