I'm afraid this is one of those `black magic' areas that the professionals
don't even agree on.
I had a similar problem with my TR6 about a year ago. I failed to re-torque
the head until about 1300 miles after initially installed. The head gasket
promptly failed at about 2000 miles. Bloody idiot!
I was very angry at having to do the job again so was determined the gasket
should not fail. After asking some TR specialists their consensus view was that
a re-torque after 500 miles, cold, was all that was required and that 6 cylinder
head gaskets fail rarely. It is essential that both the block and head are
absolutely flat. Warping of the block is rare, although possible. Cleanliness
is also important. The replacement of head bolts is normally a good idea.
I followed this advice - no problems since.
Speaking to non-TR professionals their response included:
bring engine up to normal working temperature, allow to cool, re-torque
drive 5000 miles, re-torque
don't re-torque at all(!)
One would think that after 100 years of motor cars a consensus view would have
been established for cast-iron engines! Alas no.
Giles Nelson.
1973 TR6 PI.
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