dear FOT,
I cannot remember ever having "broken " an original TR supplied cyl head
stud. I personally have pulled the threads out of the block and had to
install a heli-coil as a consequence. I have also seen the threads pull out
of a standard head nut. I have also seen the SAE threads on the upper end of
the studs deformed from overtightening or torquing with out adequate
lubrication on the threads, but as for a stud actually "breaking " into two
pieces, the stud in the peyote engine was the first, and I am quite certain
that is was a modern "replacement" stud, not an original TR supplied part.
The problem with the cracks in the block, especially from the left rear
stud hole to the right into the water jacket area, I believe is caused by
overtightening the studs into the block. The threaded hole is way deeper
than the length of the USS threads on the bottom of the stud. So when the
stud is tightened into the block, it goes down until the threads end and
then can go any further. If there is an attempt to further tighten the stud,
the threads on the stud try to pull the stud down into the block and the
unthreaded portion of the stud acts like a wedge and trys to expand the
hole. Cast iron is not to flexible and therefore a crack is the result. I
have seen so many blocks that are cracked like this, that I have come to the
conclusion that most o the damage was probably done upon initial assembly at
the factory.
My fix is to drill the hole about 1/4 inch deeper, bottom tap the hole
and then install a stud with threads that are long enough so that the stud
will actually "bottom" by hitting the bottom of the hole and not create any
"wedging " force at the top of the hole. this procedure should also transfer
some of the pulling stress deeper into the block and away from the deck
surface where the crack originates.
Regards,
Greg Solow
|