In article <9506061902.AA03999@raptor>,
paisley@boulder.nist.gov (Scott W. Paisley) wrote:
> Speaking of checking clearance. How do the cam manufactures come up
> with the tolerances for the valve lash? They seem to vary greatly,
> and rarely match the stock clearances! Is this a timing issue? Or a
> method of fine tuning the cam?
No, don't even think about it. If the gap is set to tight, you'll run
a significant risk of burning your exhaust valves. If set too lose, the
engine will become noisy and you will significantly increase wear in
the valve train. Not that I quite see the point in a lose fit anyhow,
it simply gives an overall decrease in power by reducing the lift and
duration.
The optimal gap for any cam will depend on details in the actual cam
profile.
If you want to play around with your cam, you can modify the overall
timing by adjusting the timing chain. Early timing usually improves the
top end, late timing increases torque at low revs. Don't overdo it,
though.
Egil
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