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Re: [T3] engine diagnosis


<x-charset iso-8859-1>KeithP=> how can it be possible to grind
=> anything off the lobe and not significantly
=> reduce the lift?

That'd be the case if you only ground off high part of the lobe. But as I
understand it lift is the difference between the high and low ends of the
lobe, not the height of the lobe relative to the center of the shaft.
Regrinding generally takes metal off all the way around, and the adjusters
make up what gets ground off. Given enough meat to start with you could even
increase lift with a regrind by taking more off the low end.

But the thickness of the hardness layer is always mentioned in any talk of
regrinding a cam, and I think that's the main problem. It probably never
mattered with the older engines (flathead Fords, say) and their pretty basic
metallurgy, so regrinding became a pretty common tuning procedure.

(I idly wonder whether it makes any measurable difference that a ground-down
cam lobe is moving a bit slower relative to the lifter ....)

Steven Ayres, Prescott AZ
'66 Grosse Karmann

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