> When did they delete the thermostat? Do you have a year? Even
> approximate year?
Sorry, I didn't mean to say there was no thermostat, only that it was
changed to a non-sleeved design. I don't know exactly when it happened, but
my TR4A SPC lists a non-sleeved thermostat and my factory supercession list
says it is an approved supercession for the earlier thermostat.
The casting for the thermostat housing also changed slightly, I believe at
or near the start of TR4 production (perhaps for the electric temperature
gauge sender ?). The later casting has a slightly smaller passage for the
bypass, which may or may not be important. ISTR there was some discussion
over whether the hole in the water pump housing (where the bypass attaches)
got smaller too, but I don't recall any conclusion on that point.
I've not tried to make any relative flow measurements, but even the sleeved
thermostat doesn't block off the bypass completely.
Also, it should be perfectly safe to run a fully blocked bypass, as long as
you add a hole through the thermostat plate. In effect, that will make the
bypass run through the radiator. It slows warmup substantially (depending
on the size of the hole), but provides maximum cooling.
Randall
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