Surfacing the head will reduce the clearance so the head is not the problem.
It is possible that the camshaft has been radically cut at some time or
another.
Another less likely possibility is that there is a difference in the lenghts
of the push rods versus the correct length. I have heard stories that 3
main motors and 5 main motors have different length push rods "or at least
should have". Remember the 5 main motor has 1/4 inch more stroke than the 3
main.
Personally I subscribe to the cam being over ground.
Also, as the head gets milled and the "wear bar" is no longer visible, the
top sides of the push rods actualy touch the rocker arms at extreme valve
positions. I had to grind the offending portions down to rectify this
problem on my SII motor.
J.Gross
Gross(at)unit.com
----------
From: Jay Laifman
To: DonBaby58; ALPINES
Subject: Re: Re: Valve Rockers
Date: Monday, July 08, 1996 1:46PM
FORWARDED MESSAGE from (MAIL (at) CSERVE {INTERNET:DonBaby58(at)aol.com}) at
Don writes:
"The problem is that I CANNOT attain the proper clearance
of the rocker arm to the valve by turning the adjusting
screw. The rocker arms are beyond the limit because the
rocker supports are sitting to low. The only thing I can
think of is that maybe the bottom of the head has had
material ground from it several times over the years and
now the rockers are beyond the limit of proper clearance
from the valves."
In addition to Bob's terrific comments, I just thought I would add that
as I recall there was this little round step on the bottom surface of the
head. As the head surface is machined, the step gets smaller. I think
the bottom of the step is the factory determined limit for any surfacing.
Jay
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Jay S. Laifman
Pircher, Nichols & Meeks
1999 Avenue of the Stars
Los Angeles, California 90067
(310) 201-8915
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