On Sat, 17 Jan 1998, Nick wrote:
> I think this could be a big hint...If the head is shaved and the push rod
> length not adjusted accordingly, there will be at best a little noise,
> worse, a lot of wear, and if to an extreme, breakage. When the head gets
> thinner, the push rods become (effectively) longer and the relationship
> between the end of the rocker and the end of the valve changes. At small
> amounts of misalignment, the rocker tip will push across the valve stem and
> increase wear and the valve will make noise as it gets slammed back and
> forth in the guide. In the extreme, the rocker can make contact with the
> retainer instead of the end of the valve and cause mega-wear and breakage,
> not to mention "weird" noises. This problem needs immediate attention.
It doesn't work that way. Shaving the head doesn't change the
relationship between the rocker tip and the valve stem. That relationship
is determined by the height of the rocker shaft and valve stem tips off
the top of the head, neither of which is altered by shaving the head.
Unless he machined off the bottoms of the pedestals to lower the rocker
shaft or shimmed the pedestals to raise the shaft, or unless the valve
seats are recessed excessively into the head, the rocker arm geometry
should be within normal production tolerances.
Shaving the head does, as you said, mean that the pushrods are longer than
they were relative to the distance between the lifter and the rocker arm.
This doesn't usually matter as long as there is still an ample range of
adjustment at the rocker arm screws. Shortening the pushrods is really
necessary only if the head has been shaved so much that the adjusting
screws can't be turned far enough up to give the correct clearance.
I suspect his noise is coming from something else. Worn valve guides
and/or stems? Worn rocker tips, which make it difficult to adjust the
clearance accurately? Worn rocker bushings and/or shaft? Worn lifters
and/or cam lobes? Any of these individually or in combination will create
a lot of valve train noise that no amount of adjustment can get rid of.
-----------------------------------------------------------------------
Chip Old 1948 M.G. TC TC6710 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO
fold@bcpl.net
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