timing chain jump a tooth?
11-28-2011, 04:18 PM
#1
timing chain jump a tooth? Has anyone ever seen an LS2 timing chain and tensioner setup allow the chain to jump a tooth from a backfire?
I just finished tearing down my LY6 and found the timing chain was 1 tooth ADVANCED! At first I thought I just installed it there carelessly like a dumb ***, as I did not degree it, but I did check PtoV when that cam went in and it was good.
Upon further dissasembly I found piston to valve interference marks(intake valve) on the pistons - nothing radical, but enough to know something is going very wrong.
Could valve float have caused the marks on the pistons? I dont beleive so as the piston is moving down and away from the intake valve at the position it would float???
Car ran excellent for 2 seasons?
I just finished tearing down my LY6 and found the timing chain was 1 tooth ADVANCED! At first I thought I just installed it there carelessly like a dumb ***, as I did not degree it, but I did check PtoV when that cam went in and it was good.
Upon further dissasembly I found piston to valve interference marks(intake valve) on the pistons - nothing radical, but enough to know something is going very wrong.
Could valve float have caused the marks on the pistons? I dont beleive so as the piston is moving down and away from the intake valve at the position it would float???
Car ran excellent for 2 seasons?
11-28-2011, 07:35 PM
#2
I'd think if the chain actually did jump a tooth, there'd be noticeable fretting or wear on the teeth and chain. During overlap the intake is opening and the exhaust is closing, but float keeps the valves off the seats a lot longer than intended so anything can happen...
11-28-2011, 08:14 PM
#4
there is ABSOLUTELY NO abnormal wear on the timing gears or tensioner.
I cant believe I installed it 1 whole tooth advanced, but I guess it is possible, I did the cam swap in the car, and I did not degree it, so I cant verify it was in correctly at install time.
It does seem crazy that I had .120" PtoV clearance if the cam was 16* further advanced than it was supposed to be???? And the car ran great!
I will never install another cam without degree-ing it!lol would have caught the error.
I cant believe I installed it 1 whole tooth advanced, but I guess it is possible, I did the cam swap in the car, and I did not degree it, so I cant verify it was in correctly at install time.
It does seem crazy that I had .120" PtoV clearance if the cam was 16* further advanced than it was supposed to be???? And the car ran great!
I will never install another cam without degree-ing it!lol would have caught the error.
