Quote: I would agree with the cam lobe if it was more consistent. If it was a lobe it would be more likely to do it all the time, not just under load.
Back in the Chev 305/Olds 307/Cad 4100 days I had plenty of them run half way decent till you leaned on them..then they would sound like a popcorn machine Broken/weak valve springs can do the same thing.
I hope I am wrong. A running compression test can help to isolate valve train problems that a cranking test can miss. Good luck Stu!
Broken/weak valve springs can do the same thing.
