Here's an interesting one. Back about 18 years or so ago one of the techs at my Dealer did a eng rebuild in a 318 truck. When he was done it had a roaring sort of valvetrain noise so he put STP in it and let it go as he could find nothing wrong. Truck came back a week later and had eaten the cam lobes up bad ! Anyway parts gave him another cam and after he had it together it made the same roaring noise. When I looked at it with him I noticed none of the lifters were rotating ??? So we checked everything and had parts recheck the cam part# and they said they pulled the same cam as the original RO (repair order) as they took the part# off a copy of the RO when he rebuilt the eng. Ha a little lite went off in our heads and we had them look the cam up by application and found out we had the car cam which is a ROLLER cam and the truck still used a flat tappet cam that year. I dont remember the exact year we were working with but we had flat tappets on a ROLLER cam and it dont work !! Once we figured that out and put the right cam in all was good to go. Ron