I have a 477 gas engine IT backfires through valve cover 2 and4 cy have no builds upcompression is the intake or exhaust valves bent or sticking or cylinder damage compression builds up and blows the valve cover cap off any suggestions greatly app thanks

 

Sounds like you have a hole in a piston .

Good Luck ----------------Hotwrench

 

You're going to have to pull the head at a minimum. Maybe that hole in the piston is brought on by a dropped valve.

 

hey are the 477 engines known to blow pistons? unrelated but important question: i have no crank for mine, is there any other cranks that share common main bearing spacings?

 

are 477s prone to blowing pistons?

 

hi fordpull -could it be really worn out/cracked valve guides?

 

With an engine this old it could be anything. One thing it really is though is a teardown job. Until you pull it apart, it's all guesswork.

If you are hoping to pour a can of Motor Honey or something into it, you are dreaming. Get your tools or checkbook out.