Alex
As usual, Randall has given some excellent advice which is all worth
following through. This comment is something of a long-shot but if you get to
removing the cylinder head, I'd recommend having a thorough look around the
coolant areas of the cylinder liners, especially behind #4 where it backs up
to the block. While I've only owned two or three wet liner TR's a long time
ago that were trouble-free, I've had far more recent exposure to the Ferguson
tractor engine which, while different in many ways, does share commonalties
with the TR 4 pot. The presence of 'crud' behind and around #4 cyl has caused
all sorts of frustrating problems and usually this is because the many
surviving examples of the TA and TE series is that because they're mostly used
in comfortable outside temps, many owners literally use straight tap or rain
water as a coolant. In areas where high levels of lime are present in the
water supply, this leads to rapid lime build up and
obviously restricted water flow which in turn brings on other problems.
As I
say, this is a long-shot and if you are running pure tap or rain water as your
coolant, the addition of year round anti-freeze with its 'crud annihilators'
would be sensible - even if you do live in a hot year round climate.
Jonmac
http://standard-triumph-books.co.uk/
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