FWIW here's my experience. I rebuilt my TR engine around 1981. The car had
covered around 70k miles but had been shockingly maintained. The build
included a crank grind, thus new main and big end shells, crack testing of
conrods ect, new rings, cylinder head overhaul, timing chain and tensioner
and that kind of thing. Since then it's done another 70k mostly trouble free
miles on Castrol GTX oil changed yearly for the most part. Oil pressure was
adjusted on initial assembly to 70psi engine hot at 2,000rpm. The book
figure.This would drop to 30-45 at idle depending on idle speed (600-750) .
After about 20 years and 50k miles the oil pressure during a long hot fast
blast down a continental motorway would decline to (typically) 50psi at
3000 rpm and 10-15 at idle. Pressure would improve after you left the
motorway for normal roads.
The Haynes manual suggests changing big end bearings at 50k miles and I
remember Cox (or was it Buckle?) telling me if pressure drops to 50 it's
time to do something.
So I fitted new shells and also replaced the oil pump gears and had the
coverplate surface ground flat. This restored the oil pressure to 70psi at
2000rpm and 35-40 at idle in all conditions and it's now about 15k miles
later.
OTOH I've been told that so long as there's some oil pressure these 4 pot
engines are virtually bomb proof so don't bother rebuilding until you can't
stand the banging and clattering of the bearings, pistons, chains, blue
smoke ect any longer.
Other listers experience and views would make interesting and instructive
reading I think
Happy New Year to all again!
David Brister.
(45F and raining cats and dogs on the Cote d'Azur!)
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