258 Backfiring through the Carb

This is actually an '84 CJ7 but I found that the people on this site are more knowledgable than most others. My son sold this Jeep to a kid down the street.The 258 is bored .040,mild cam,Clifford header and intake with a 390 Holley, TFI ignition upgrade. Somehow the kid bent a pushrod for the #2 cylinder. We changed the pushrod and it was backfiring through the carb. When I remove the #2 plug wire it stops. Compression is between 120-125lbs. on all 6 cylinders. I changed the power valve in the Holley but really didn't think that would be it and it didn't make any difference. Anyone have any ideas??

 

missing/popping at idle ?
only on acceleration ?
intake or exhaust push rod bent ?
other rod okay ?

 

Based on the bent rod in #2 and the fact it stops backfiring when you pull the #2 plug I would guess at a messed up intake valve on #2. Only way to know for sure is to pull the head.

 

It pops at idle and worse as you accelerate. As I recall it was the intake pushrod that was bent and the exhaust was fine. I asked him if he had over revved it and he looked guilty and said "Maybe".
HudsonHawk I was wondering the same thing. I was thinking the compression test ruled it out but while running it might bejust enough to be backfiring. I have a complete set of Neway carbide valve seat cutters along witha Siouxe valve machine(for grinding the valves themselves),magnaflux equipment etc so I guess I'll have to pull the head and take a look.

 

I agree with Hudson, bent/hanging valve. Something had to make that pushrod bend, they don't do it by themselves. Be sure to do a thorough investigation for other broke parts, debris, etc.