George,
"Torque to yield studs" were employed in the '80's by Ford as one of their
terrible "better ideas". The intention was the stud would stretch as it was
tightened, but would only retract back very slightly when removed. Their
"effectiveness" was largely responsible for thousands of cracked heads and at
least one safety recall if the head should crack on the exhaust manifold side
(leaking oil + hot exhaust manifold = fire).
Ford was so remiss in informing mechanics of this innovation, that some of their
own dealers as nearby as Ypsilanti, Detroit and Ann Arbor, MI were unaware that
studs were never to be reused or re-torqued. The results of reuse was head
cracking and warpage.
I have never seen nor heard of any instances where MG made use of them.
Jim
Gonaj@aol.com wrote:
> Is it possible that these are "torque to yield " studs. I know that most
> modern engines use that type. I have a large gap in such experience with
> head bolts, I know that in the 60s and before they always provided torque
> specs but when working on a 1985 engine I learned of "torque to yield " head
> bolts. These must only be used once, and there is a specific instruction in
> the manuals for them.
> If you are sure that this is not the case, look in the front of any Haynes
> manual and you will find a list of torque specs for bolts according to their
> size. Do not exceed this as you will weaken the bolt.
>
> George
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