Thanks Jerry! I ran across this post of yours on adjustment.
If there's a brass float in the carburetor, that backfire might have collapsed it. You might be experiencing a little flooding, resulting in the rough idle. Just a thought, as you've pretty well covered all the ignition-related problems. I believe all the 292's had hydraulic valve lifters, which require a pretty simple adjustment procedure. Each cylinder is brought to top dead center on the compression stroke, (engine stopped) the valve adjustment is loosened until the pushrod is sloppy, and then tightened to just remove the slack. Then tighten an additional 3/4 to 1 turn. (both valves). Turn the engine to TDC on the next cylinder in the firing order, and repeat until all cylinders have been adjusted. Don't try a running adjustment, it's sloppy and inaccurate!
Jerry
What you've said is inline with someones description on the ChevyTalk forum.
Rotate the engine until the #1 exhaust valve has just started to open. Set the #1 intake valve.
Rotate the engine again till the next exhaust valve just opens (not the one on the cylinder next to the one you just set, but the next one that opens anywhere.) Set the intake adjacent to it. Continue to do this until all the intakes are set.
Now rotate the engine till the #1 intake valve is about to close. Set the adjacent exhaust valve. Again rotate until the next intake is about to close and set that exhaust. Continue until you have set all the exhausts.
Of course you don't have to start on #1, and on a V8 you can do one side then the other. Or if you want you can just work your way from front to back or any other order you choose. Just be sure you do all them. If you get lost, just rotate the engine till you see an exhaust open or intake close, and start setting again.
Most hydraulic lifters should be set 3/4 to 1 turn past initial contact, though some performance lifters call for 1/2 turn. That will put the lifter plunger in the correct position.
When you say the pushrod is sloppy do you mean it moves up and down? or rotates? Also you mention both valves. Does that mean intake and exhaust for the same piston? Just looking for some clarification between what you posted and this other individual. I think you may both be saying the same thing.
