> I've
> never heard of taking a car back for it's 1000 mile re-torque. Maybe
> they did this years ago, pre-war?, but I don't know.
It's been done on at least some post-war cars ... the owner's manual for my
59 TR3A has it listed as a maintenance item. ISTR my 71 Stag does too.
> Does everybody always retorque?
I usually do, although I've not built a race engine.
> Why don't new engines need this?
Others have already given better reasons, but I suspect at least one reason
is that it's cheaper for GM (for example) to service the occasional blown
head gasket during warranty (and it does happen); than to pay for the
dealers to retorque the heads.
> Only the cylinder head?
Yup. Cylinder head is the only place on a car with those kind of pressures
involved.
> Inquiring minds
> want to know, plus I'd like to be able to give my client an answer.
Might be worth taking a peek at the shop manual or owner's manual for the
XJS. Some small chance it's in there ... otherwise I'd explain it as an
extra service that is generally accepted as lowering the chance of a blown
headgasket. It's not an absolute requirement, most likely the engine will
be fine without retorquing ... but you won't guarantee the head gasket if it
isn't.
YMMV, etc.
Randall
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