swollwick

my car's starting to have a serious problem. It's sort of backfiring, but most of the time it's more of a popping. It doesn't do it every rotation, it's sort of sporadic. Just changed all the plugs and wires. And it sounds like there's no skip at all. Any thoughts? Thanks for the help

I cut the pipes just in front of the mufflers. could this be my problem? I've been told that could mess up my valves

angel71rs

When did problem start, b4 or after plug/wires change, b4 or after you cut the pipes? Anytime I hear of a mid 70s chevy starting to run rough, I always ask if it still has stock cam in it. They had problems with lobes rounding out in those years, but never personally seen it on a 74.

Cutting back pressure can lean it a bit, but not enough to burn any valves. You would have to have been lean to start with.

byrons1502

sounds like a valvetrain prob. with the newer oils they have less zinc and is killing alot of hydraulic cams. i would not be surprised to see a worn lobe or sticking valve. we just had a 70's 440 have a bent pushrod doing the same thing. pull the valve covers and rotate the engine while watching the rocker arm.

Z28SORR

I'd check out the rest of the ignition before I jumped into the valve train.
Have you check the cap/coil and rotor, timing, timing advance, etc?
I think the "zinc" problem has been way over stated.

byrons1502

just had a brain fart. check for a lean back fire first. ignition system second. camshaft third

jasonspd

I had a hell of a time finding an intermittent backfire in my '69 Camaro a few years ago. It was rare and only backfired once every 15 minutes or so and it ran fine. Turned out to be a bad condenser in the distributor. Just a thought.