Compression question

Dana67Dart said

If a valve keeper is missing wouldn't the valve be hanging open and posably be hitting the piston?
Backfiring out the carb would sugest intake valve open.
Was the missing keeper on the intake of #3?
Bent push rod sugests valve hit piston.

Click to expand...

I think he may mean the 'clip' in the top of the lifter was missing; that would allow the lifter to pump up, push the valve into the piston, and bend the pushrod. If this happened, OP, the #3 intake valve could now be bent and would indeed cause the 0 compression and the intake backfiring.

As for #6, it certainly could be valve's badly sealing. Or it could be the rings. Go back and compression test #6 again. Then put 1/2 to 1 tsp of oil into #6 via the spark hole, and test compression again. If the numbers rise with the oil added, then you probably have a ring issue; if they stay the same with the oil, then look at the head/valve area.

Sounds like the heads are coming off regardless of where this goes. At that time, the cylinders can be inspected/ measured.