Help please

A flat cam lobe on the exhaust will also duplicate the issue described by Tom. Under slight acceleration you'd hear a "pop,pop,pop every time the related cylinder was on its intake stroke, not really intermittent, consistent under the right conditions.
 
100IH said:
A flat cam lobe on the exhaust will also duplicate the issue described by Tom. Under slight acceleration you'd hear a "pop,pop,pop every time the related cylinder was on its intake stroke, not really intermittent, consistent under the right conditions.
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That's right. The last time I ran into the flat cam problem was back in the 70's when I worked at the GM dealership, and Chevy had some soft cam problems.
 
Get a grip, everyone.

If you wanted your car to make a loud backfire when you're "driving along," your support group would tell you to turn off the key for just a moment, then turn it back on, i.e., momentarily interrupt the primary ignition circuit. Isn't that probably what's happened here? Before searching for exotic compression tests and blown gaskets and such, there is a whole world of simpler and more likely wiring issues to be eliminated.

Too bad that intermittent breaks are such a pita to identify. BUT, every single electrical connection in the primary ignition circuit needs to be checked and re-tightened--from the batttery posts to the fuse to the ammeter to the coil to the ignition key to the points to the pigtail to the ground path back to the battery. Most likely, an intermittent interruption but possibly a short to ground as well.

Since the backfire did not occur under load, problem is probably not in secondary, high-voltage circuit (e.g., carbon tracks in distributor).
 
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ok , pulling the head . cant find anything else . the compression is still weird . recent overhaul (complete) . 2-3 are @ 50# dead on ………. 1-4 are @ 75# dead on . done warm .
going to see what's there . will let you know when I know . thank you all ….
 
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