Cam Timing Accuracy

[Straight Six]

I appreciate that anything is possible, but is it likely that the camshaft drive gears wear enough to significantly affect valve timing? Although my engine has been re-built, the cam drive gears are original and will have done 150k miles. Obviously the chain has been changed several times!

[StagNL]

Theoretically I'd say it is possible, but probably not noticable.  The same goes for over-skimming a OHC head.  In both cases the cam and valve timing is retarded in relation to the crankshaft.  I'd wager that it would be possibly more retarded in the latter case but still not really noticable.
For what it is worth, my Stag engine has its heads at or just beyond the factory stated limit in head height due to skimming prior to my ownership.  How far out is it I don't know.  Maybe a degree give or take a fraction.  Runs fine.  Now you've got me thinking - got to work out how far out it is just for the record.

[Nick Jones]

Chains can stretch enough to have a noticeable effect (single row anyway) but doubt the sprockets would wear enough.  However, the little one does get quite hooked sometimes and this will increase the rate of chain stretch as it doesn't mesh properly any more.

Nick

[Straight Six]

Thanks for the replies chaps. It was the hooked appearance of the gears that got me wondering and having never seen new, unworn examples of the gears I wondered I had nothing to gauge the amount of wear against.

As the gears don't seem to be readily available and the chains are so cheap (almost worryingly cheap...) I'll carry on as I have been.

[69vitesse]

Fit a duplex chain kit and forget about it.

If you're after some lower miles OE gears and are anywhere near Portsmouth, I'v got a gash 2l six I'm going to weigh in you can have.

[piman]

Hello Straightsix,

a new chain on worn sprockets won't last very long, a duplex as suggested seems to be the way to go?

Alec

[Nick Jones]

Agree - get the duplex set from a 2.5 - fit and forget.

Nick