I just had the valves replaced on a cylinder head for a j20a DOHC interference engine.

I'm trying to align the camshaft sprocket to the markings on the cylinder head, but they snap back to where they were once I let go.

It's from .5 to 1 tooth off.

The question is, how many teeth is acceptable before you see valve damage?

  • 2
    You want zero teeth off, no exception. Not that you'll get valve damage, but it will not run correctly if it isn't right. Jan 13, 2017 at 23:16
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    Use a spring clamp to hold the chain to the sprocket until you're ready to take up the tension (haven't got a manual for this engine, so don't know what that will look like). The springing back is due to that side being on the lifted cams. Once you think you have it, turn the engine over manually by the crankshaft pulley a few times; that way, if there is interference you'll feel it by hand, and you won't cause any damage.
    – PeteCon
    Jan 14, 2017 at 3:38
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    Use a wrench and some quick ties that's what I did Jan 16, 2017 at 12:01

2 Answers 2


In my experience, you get at least one or two teeth out before the engine is physically damaged. However, I would suggest you look into whether or not your engine should be temporarily fitted with a cam locking tool during timing belt replacement.

I'd also strongly advocate turning the engine over by hand prior to attempting to start it so you know for certain that it isn't mechanically locking up internally.


given the word "interference" then I would assume that there is little or no room for error on the timing. Interference for engines tends to mean that the valves occupy the same space as the pistons at different times moving out the way as the other arrives. The springs closing the valves can cause the cam to rotate away from the timing point, so there is usually a hole to lock the position while you fit the chain, you will need to check the manual for the correct procedure.

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