Low oil pressure, 12vane waterpump, engine rebuild

[Mike Wattam <101714.1343@domain.elided>]

Dear Ralph

Top marks for buying two.  When do they let you out of the clinic?

Your queries;

OIL PRESSURE
Chances are, the oil pressure relief valve is stuck partly open.  Take 
off the oil pump (not easy!) and remove top cover, the dismantle 
pressure relief valve.  You will probably find one side of the barrel 
polished and worn, the other side almost rusty!  A new barrel and 
spring might do the job for you without anything more major.  You 
can actually see the small disc and split pin on the pump cover from
under the car, so it is possible to do this without taking the whole 
pump off (and the exhaust as well to get at it) but I wouldn't 
recommend it.

Oil pressure is a bit of an illusion anyway.  If the car is running fine
with no rattles, and the oil pressure suddenly drops, chances are
it is the relief valve.  But if it just runs on ow pressure for sa long
period, clearly the oil is getting round the engine lubricating and 
cooling it nicely, so why interfere with that.  Conversely, high oil 
pressure could mean tight bearings, not allowing oil round the 
engine because the relief valve blows the oil back into the sump.

The only things likely to suffer because of low oil pressure are the 
cylinder heads.  Their oil supply comes from excess pressure 
from the main bearings.  If the main bearings and big ends are 
sloppy, the oil will tend to tip back into the sump rather than go up 
the engine to the heads.

ENGINE OIL COOLER
A good idea, but fit one which uses an in-line thermostat so the oil 
does still warm up quickly.  Do not fit the type which is a spacer 
block on the oil filter housing, for the Stag, TR7 and Sprint there 
is an adaptor block which goes on the oil transfer housing (next to 
the oil pump).

WATER PUMP
The 12 vane gives no noticeable improvement over the 6 vane, 
so I wouldn't bother to do it.  The TR7 pump is the same, but the
cover is different and won't go on the Stag block.  New covers can 
be bought from UK Stag specialists.

OTHER MODS
Look carefully at your radiator and have it cleaned out and checked 
for pressure (Stag runs at 20psi so it's got to be good!  Do NOT 
have a new core fitted unless absolutely necessary, as the original
type radiators were of a construction that is not made today and 
finding one that will give good airflow and cooling capacity is not 
easy.

Finally, if there is no radiator cowl already fitted, this should be 
done.  Glenn Merrell one of the other respondents in this group 
is very entrepeneurially having some made and you should fit 
one of these (to each car?).

Mike Wattam
Triumph Stag Register