big block duster misfire

Same car as in my other posts: '75 duster with a '73 400 big block 4 barrel/727 auto/8.75" combo with a cam (don't know the specs) and new mopar performance electronic ignition distributor with mechanical and vaccuum advance. Runs smooth since I installed the new distributor, but there is an intermitent kind of "pop" noise that comes from the driver's side cylinder bank occasionally. It is not rythmic so I am thinking a misfire, maybe? The engine runs smooth though, so at first I just chalked the noise up to the crappy, leaky exhaust system. However, the other day I removed said exhaust at the manifolds and couldn't resist the urge to fire it up with no pipes. The noise is very noticeable now and when it does it a small flame spits out of the driver's side exhasut manifold. In addition, after I rev the engine and it is on its way down the rpm range, it pops loudly and blows considerably louder flames out of the manifold. I have been told that this is normal, but I am skeptical. Also, the engine smokes just a little, I'm thinking either worn rings or valves. Could this maybe be linked to the "misfire" I'm hearning? Could I be wrong and the noise could be something besides a misfire? Any advice would be appreciated.

Reply to
sackattack84
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Just speculating aloud...

Wonder if a leaky exhaust valve would let unburned air/fuel into the header during the compression stroke, then when the valve starts to open on the exhaust stroke, the little bit of unburned fuel/air ignites?

Reply to
Marcus

kinda what I was thinking too. I guess I'll have to pull the heads and find out what condition the valves are in and check the cylinder walls for wear while I'm at it

Reply to
sackattack84

An exhaust leak could cause it to pop, I'm assuming it has headers with a

400 conversion their should be a gasket between the head & ex flange Check the plug wires very carefully for burned spots. If you don't have them check the junk yards for some of the GM metal spark plug insulators
Reply to
sqdancerLynn

I bought a set of these for my 55 Chevy and it was the best deal I could find. They not only perform well but look nice too. Stainless braided

Reply to
Abby Normal

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