After reading this forum for some time I know there are many of you that can provide some valuable advice to this part timer. The symptoms are a miss or skip. From the engine bay it sounds ok at a steady rpm but you can hear "popping" from the exhaust.When you give it gas quickly it really sputters and will sometimes backfires through the carb. Ithought it was a vacuum leak but could not find one with carb. cleaner. Then I covered the primary inlet of the carb. with my hands and it shut off immediately (so no vacuum leak?). Timing is set at 14 initial and 34at 3200 rpm.I have checked the plug wires and all seem secure.I pulled the dist. cap and the contact on the rotor appears to be a little "burnt" for lack of a better term. Should I pull the plugs and inspect?What I am running is a 347 with Dart Pro I heads, Pertronix dist., Holley 650 dp by AED all new. The motor only has a few hours on it. Any suggestions? Does it sound more like carb. or ignition. A small exhaust leak would not cause this would it? (I have a small leak).

 

A small exhaust leak could cause the exhaust popping, but wouldn't explain the backfiring through the carb. A vacuum leak might. Did you set the timing with the vacuum advance disconnected and plugged? Improper timing is another possibility. Also, did you adjust the valves yourself? You may want to go and readjust them.

If the ignition contacts are burnt, clean or replace them.

 

The popping is coming from the tail pipes (as well as under thr hood). It's funny you mention the valve adjustment. I am not sure the noise that I hear under the hood is an exhaust leak. Could a loose rocker sound like an exhaust leak? Would this cause the "miss"? Thanks again.

 

a bad exhaust manifold gasket sounds like valve ticking
as starfury says make sure to plug all vac ports on carb and check the timing without vac advance disconnected (and plugged)
if you have connected manifold vacuum to your distributor instead of portwed vacuum then you'll run into all sorts of problems.
When blocing the inlet of carb and engine switches off it's unfortunately not a sign of vac leak.
See it this way if your manifold would pull air somewhere and block the carb, the engine would be able to pull air, but couldn't pull gas from carb. At least I believe so.

i believe your timing is wrong.
maybe you are one of the lads where the harmonic balancer slipped and the timing marks are wrong.
check "timing marks" post from today.