marty sukey wrote:
> Ken,Jack, all. Is this a problem specific the the TR4 engine or is this
> something the TR6 and Spitfire folks should keep in mind?
>
>
The TR6/GT6 engines have the rocker shaft supports at the ends of the
shaft, so that's a plus. Nevertheless, the pedestal studs are a bit
wimpy. One of the things I've been thinking about is the tendency of
the pedestals to walk back and forth with increasing valve spring
pressure. As one adds stiffness into the valve train--stronger and
stiffer pushrods, stronger rockers, etc., there's usually little done to
the pedestal studs, and that means the weakest part of the valve train
is the one to flex.
In looking at the pedestals, it's apparent that they are mostly hollow,
with a collar cast into the tops, which fits somewhat loosely around the
stud. That means the pedestal, under load, can sort of squirm underneath
the nut and washer, which might be one of the reasons for the nuts
loosening up.
What I'm thinking about doing is boring that collar out to a slightly
larger size, enlarging the stud threaded bores in the head, then
installing a larger stud that fits snugly inside the pedestal hole.
That also allows larger nuts, and considerably more applied tension to
hold the pedestals in place. I think that milling the feet of the
pedestals perfectly flat and 90 deg. to the stud holes will help a bit,
since they seem to come from the factory without precise finishing and
over time may deform a bit and allow the pedestal to rock back and forth
under load.
Cheers.
--
Michael Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking distance....
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