Compression test done. Perfect/equal compression across cylinder 1-3, but cylinder 4 had 0 compression. Leak down test done & it appears to be coming from the head/inlet side.
Head has to come off. Expected to see a burnt valve but no. Removed the cams which had signs of wear & sent the head off to be inspected. Head looked fine....So dropped a piston just in case & that too came out fine. Missing something here???
Dummy assembled head with the cams. And the problem presented itself. The cam wear, wore down the journals too. Clearances look ok on the bench, but when you spin the cam, the cam began to rock & subsequently closed clearance & opened the valve. Could see some evidence down the line too.
These HKS 272's are 13yrs old & are known to be "soft" & fail on numerous applications. So I think I'm going to bite the bullet & go for different cams & touch up the tune. Leaning towards Kelford Gen3 272's with 10.8mm lift in/ex (VS 10.18mm lift of the HKS cams).
Thankfully, pistons & rings are ok too.
As a precautionary measure, will change bearings due to some minor metal shavings from the cam failure. Will need to have the head tunnel bored.