[TR] 4 vs 6 vane water pump impellor

[Randall]

> Oh Fountainhead of such unquestionable knowledge, may I most 
> respectfully
> suggest you do a quick spool-back and exclude the Stag V8? :)

You are quite right, John, I was thinking only of the TR2-6, not the Stag nor other Triumphs that I have no experience with
(Spitfire, Herald, etc.).  I should have been more explicit.

> It's 
> bete-noire was
> cooling. Period.

I agree entirely, and yet I still feel that lack of water movement was not it's primary issue. Cooling systems, like chains, are
only as strong as their weakest link.  The Stags' biggest cooling problem (ignoring things like casting sand left inside the coolant
passages and heads that leak combustion gases into the coolant) appears to be lack of air flow through the radiator, combined with
insufficient surface area of the radiator.  The body design has limited area for air to flow into the radiator, and a largish open
space underneath the radiator that I believe allows air to "pile up" in the space behind the radiator, further blocking air flow.
Some folks have even observed that upgrading the radiator can be counter-productive, as the increased fin and tube count further
obstructs the air flow through the radiator.

As I'm sure you know, the Stag underwent several major redesigns of the cooling system.  Practically every component was changed at
least once.  And yet, the water pump itself was not changed during those early revisions.  They did eventually switch to a 12 vane
pump, but that was much later (after the Stag was no longer imported to the US).  The reasons for that change are debatable, but
since there were no other cooling changes at the time, the theory that it was a "parts consolidation" effort makes sense to me.

I own an early Stag, with the early cooling system completely stock except for a recored radiator.  When it runs hot, the water
coming back from the radiator is still almost as hot as what went in.  If the water flow was the limiting factor in cooling, then
the water coming back would be significantly cooler.

So, for TR2-6 and Stag, I still feel that lack of water flow is not the main source of cooling problems.  I've not tried running a
12 vane pump on my Stags; but I have tried going from 4 to 6 on my TR3, and it made NO detectable difference in cooling.  Once I
found and fixed the real problem, all the cooling problems disappeared like magic, even with a 4 vane pump.

YMMV of course.

Randall