Ive got a 1978 460 that has been sitting and im trying to bring back to life. I got it running but could tell it had a miss so I changed the plugs. Drove it around the block and it backfired thru carb and sounded like I had a major vacuum leak. First I thought timing so I set it at 14°btc. Listening to it run it sounded like an intermittent miss so I was thinking stuck valve. Did the dollar bill over exhaust pipe and sure enough tried to suck it back. So I did a compression check and found the bad cylinder had approx 75psi on all except one and had nothing. Pulled valve cover and found my pushrod is gone could it be in valley. If it was ran like this before would it have caused any major damage.