Sharp popping from exhaust

[Rick Parker]

The last couple of times I have started the car and begun to drive I fell like it is hitting on 7 cylinders at low RPMs (<2000) and I get some very sharp irregular popping from the RH exhaust when I accelerate. After the engine gets the least amount of temp (in as little as 1 or 2 a minutes) this ceases. I am inclinded to think there may be some debrit in a fuel passageway that is intermitantly blocking the idle fuel jet. #1 cylinder seemed to be the least affected by idle mixture screw movement. I pulled the idle jet and it was clean.
Ideas??

[Gaz64]

Rick, could be a spark plug problem, swap 2 plugs first bank for bank.
Then if it's still the same bank swap your suspect carb with the other corner, levers should be the same.

Could also be an inlet valve guide / ring issue in that cylinder.

Test your leads as well.

Are you loosing any coolant?

You'll prove it to one of these after some swaps, best of luck with your search.

[patrickt]

Originally Posted by Rick Parker

Ideas??

You can isolate which cylinder is the faulty one by starting your engine cold and then use an infra-red pyrometer ($50 or less at Home Depot) to monitor the heat rate gain on the primaries, right at the outlet from the head, for the four cylinders on the right bank. The offending cylinder will lag behind the other three on the temp gain. Then, once you know which cylinder it is, I would switch the plug and wire for that cylinder with the one next to it (obviously not changing the firing order, just switch the plugs and wires). If the problem cylinder changes, then you know it's one of those two items. If it doesn't, then inspect/replace the distributor cap. If that doesn't do it, then we'll think harder.

[Rare Iron]

I experienced something like this years ago in a fresh rebuilt motor - it was popping at 3/4 throttle & was not running strong. At about 400 miles, it dropped a stainless valve into the cylinder & destroyed the motor. It was later determined the valve keeper was defective. Man, I hope that doesn't happen to you!

[rustyBob]

sounds like a tune up problem, check the easy stuff first cap,wires,plugs, then move to fuel delivery then the major stuff if needed.

[Rick Parker]

I checked the plug wires, and the plugs they were all OK, one wire needed to be adjusted to fit tighter on the plug terminal. Popped off the distributor cap and found the remains of burned dieletric grease on the tip of the rotor and on each brass terminal inside the cap. I cleaned it off and verified that the rotor was making contact with the center button (which it had been). The rotor and cap are both in good condition having logged about 300 miles.
I removed the rotor and realized the flyweights were not moving freely, they were binding on the pivot pins. There was also evidence of a minor bit of corrosion on the springs and their anchor pins too, then I remembered I had blown an upper radiator hose last fall and in never opened the distributor to dry it off. There was that sticky filmy feeling (dried coolant) on the flyweights and the black pads they rest on. So I removed them and cleaned everything with a little stainless wire brush, bead blasted the flyweights clean, lubed them up and put it back together with new springs. Resynced the carbs and off I went. With the mechanical advance working properly the throttle response was back as I remembered it. Life is good. Thanks for your suggestions.

[whichonetodrive]

I had the problem with exhaust popping on the right side everytime I shifted hard and sometimes when I started the motor. I found it was only the connector from header to exhaust pipe loose. I went thru everything ( carb, plugs, wires ) I had 2 loose bolts after fixing the problem no more pop

[rustyBob]

Its funny how the little things will throw you off like that.........glad to hear it wasnt something major.