Page 41 - Dec 2022

find, made of standard carbon steel.
The torque specified by Jaguar placed these studs
near their maximum capability of tensile stress. Steel
under these conditions over long periods exhibits a
property known as ?creep?. In other words they
stretch! This is not so much of a problem for short
studs or bolts but since creep manifests itself as
micro-inches/inch of length, the longer the stud the
greater the total elongation.
You don? need too much of an imagination to see
t
that this is going downhill fast. (Sorry if I let too much
engineering ?creep? in here ) The end result of all of
this was either coolant leaking out from under the
head nuts or outright head gasket failure.
I was seeing the former. Be thankful for little favors.

Problems are Always in Need of Solut ions

The solution at first blush seemed pretty straight
forward ? just buy a new set of studs as they
appeared to be available from a number of sources. I
ordered the first set of studs and found that they
were a very sloppy fit to the threaded holes in the
block.

The threads on the studs had been over cut reducing
the diameter of the stud by an unacceptable amount
and resulting in a loose and, therefore, weak fit. A
second set of studs from a different supplier had the In times of emergency, it's
same problem. Lathe Man to the rescue.

Applying full torque to the head nuts could
conceivably pull the stud right out of the block leaving
you with a strange looking boat anchor. The back-up
plan was to custom make a set of studs that actually
fit correctly.
You Have t o Have a Plan

I ordered the necessary length of 7/16 rod in 4140
chrome alloy steel., a bit of an upgrade from the OEM
Leaving the rest of us to deal, 50 years later, with
material. I then enlisted the aid of a machinist to cut
what they so casually wrought.

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