I read the article on compression, very informative. I however recently assisted my father-in-law in putting together a stump pulling 421 stroker. Well all was fine until the blow by showed up. What we found were No 4 & 8 pistons burned. Now we are not pro engine builders, but definitely not novice either. Been doing this for some time now. In fact I am currently running a 347 stroker in one of my Mustangs. The timing and everthing are within the allowable specs for the cam. I was just shocked to find 2 pistons burned like this. This engine has less than 5000 miles on it.

750 Holley and 104 octane fuel.
Lunati parts.
Any insight will be greatly appreciated.