[TR] One last question

[Randall]

> Are you trying to tell me that the factory stopped putting sleeved 
> thermostats in the TR2-4A engine before the TR4A was discontinued???

Yes, I am.  And the later, non-sleeved thermostat was listed as a factory
supercession for the earlier sleeved thermostat.  They even changed the
illustration for the TR4A parts manual (although IIRC the thermostat change
came before that).

> What good is the radiator if 
> a significant part of the coolant gets circulated through the engine 
> without visiting the radiator?

How do you know it is "significant"?

All it takes is "enough" through the radiator.  Once the radiator tubes are
the same temperature as the water, then forcing more water through does not
help and may actually reduce cooling.

I have experimented several times now, on 3 different TR3/As with various
stages of cooling problems, and found absolutely no improvement in cooling
from blocking the bypass either partially or totally.  Many American cars
leave the bypass open all the time, as do the TR6, early Stags and, I
believe, early TR7 as well.  I don't know about the TR8 offhand, but being a
GM design I'll bet it leaves the bypass open as well.

Also worth noting that the TR4-4A thermostat housing has a smaller opening
for the bypass, providing more restriction.  But my experiments were done
with a TR3 housing.

I do have several NOS Smiths aneroid tstats on the shelf, as well as a TR4A
thermostat housing with the smaller passage.  Never seen the need to
install, so there they sit.  My bypass is open, and I have no cooling
problems even in 100F+ ambient, prolonged stop and go traffic.  (Not too
many weeks ago, it took me some 1.5 hours to drive 20 miles in rush hour and
the friend I was meeting told me that his dash thermometer said it was
110F.)  The cooling system will take the heat much better than the driver
can !

Granted, my cooling system is no longer exactly stock; I installed the
electric fan while fighting with overheating problems (which were later
discovered to caused by a bad radiator), and I added a recovery bottle from
a TR4 just because I was tired of worrying about whether I was losing
coolant or not.  The 10 psi cap was also added while fighting with the bad
radiator.  But the bypass did not seem to be the limiting factor then, and
it still doesn't now.

PS, I also didn't see any difference with 3 different designs of water pump.
There are some comparison photos at
http://goo.gl/5Ockf
I'm currently running a 4-vane aftermarket pump similar to the one shown in
the photos.  (The one shown started to leak about a year after those photos
were taken.)

-- Randall