Cam Failure Details
Cam Failure Detail
(click on thumbnails for larger image)
Root cause: chamfer at base of tappet?
1 Exhaust - Opening side / Closing side
1 Intake - Opening side / Closing side / tip of lobe / Closing side again - there's a little galling on the opening side that you can't feel but can see, there's more galling on the closing side.
2 Intake - Opening side / Closing side - just a touch of galling on the closing side just past the lobe
2 Exhaust - Opening side rotating through Closing side - closing side badly galled
3 Exhaust - Opening side rotating through Closing side - closing side badly galled
3 Intake - Opening side / Closing side - you can see the galling just starting
4 Intake - Opening side / Closing side
4 Exhaust - Opening side (x 2) / Closing side
Tappet detail (2 Exhaust tappet) - tappet diameter: 0.937", base diameter inside the chamfer: 0.885", as nearly as I can measure it. Also, the base is slightly curved - if I place the base of one tappet against another, I can rock them a bit.
Here's what stock tappets look like - the base it totally flat (if I put two together, there's NO rocking), and there is no chamfer to speak of at the edge
Side wear pattern of a couple of the lifters pulled from the race motor: