> This discussion of how to set valves is all well and good, but it
> calls to mind a different problem that has always worried me. One
> supposes that the non-lift part of the camshaft's rotation is round,
> but supposin' it isn't?
I agree it's possible. More likely due to a badly cut cam, IMO, than wear,
since there's almost no pressure on the cam base circle. The lobe tips
should wear long before the base circle does.
> A simple experiment will do. Set or measure the clearance at
> different places in the rotation, see how much it changes. I'm too
> lazy to do this directly,
Me too ... I'll let someone else worry about it.
> But I've noticed the quality
> of the job I've done being different from session to session, and
> suspected that the world, er, I mean the cam, isn't as round as it is
> made out to be.
If you always set in the same position, then the results should always be
the same even if the base circle isn't round.
> Either that or my feeler gauges aren't always the
> same thickness.
"Feel" counts for a lot when setting valves. I can still force the feeler
in and out with the clearance noticeably less than I normally set, and still
feel resistance with it more than I normally set. You also have to be
careful you aren't turning the feeler in the gap, or you'll always feel
resistance.
Wear in the rockers can also make a big difference. With a badly worn
rocker & shaft, moving the rocker just a few thousandths side to side can
make a big difference in the measured clearance.
> Or the world actually changes temperature.
If you don't like the weather, wait 15 minutes and it will change !
Randall
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