Craig,
Here is a link to the Stewart's Website that has what looks like the
straight scoop in this subject.
http://www.stewartcomponents.com/techtip3.htm
Check out the other related tech tips too.
Note that the Stage 2, 3, & 4 pumps don't have built-in bypasses, which
necessitates having the 3/16" holes (3) in the thermostat. My experience is
that these holes make the engine warm up VERY SLOWLY. I have modified my
thermostat to have a much smaller hole (just 1). It helps clear the air out
of the system and makes it easier to fill with coolant when cold. (Not that
I ever have to.) But, if you don't have some kind of bypass, the coolant
will sit stagnant in the engine until the thermostat finally opens, which
will undoubtedly have some bad consequences in terms of localized hot spots.
I also remember seeing another Website that had much the same explanation
with regard to the flathead Ford engines, which had heating problems that
were cured by putting flow restrictors in the outlets from the heads. This
apparently led to the false conclusion and ensuing myth that less flow is
better because "it gives the coolant more time to cool off in the radiator"
or variations thereof. BTW, with regard to the "loose belt" comment by
Chris Williams, I assume he was making jest with a little in joke.
As the above link says, modern cars have the cap on the low pressure side
of the radiator. On my Tiger I have a three-pass radiator and the cap is
between the first and second pass. With the usual single-pass radiator on a
Tiger, Cobra, or whatever older vehicle, I would suggest reconfiguring, if
possible, with the cap and reservoir/overflow on the low pressure side of
the radiator. There is inevitably some compromise in the water pump between
low rpm and high rpm operation, but with the advanced HiPo impeller design
I think you get good enough low rpm flow while avoiding cavitation at high rpm.
Hope this helps shed a little light (not heat) on this subject.
Bob
At 05:48 PM 1/19/00 -0800, you wrote:
>Bob, Steve, et al:
>
>Being an engineer, I have this deep seated need to understand the basic
>physics
>behind the various hints, wife tales, tips etc. But, this one about
>"slowing the
>flow for cooler running engines" completely baffles me. The wide spread
>accepted
>explanation is that the water has to remain in the radiator long enough to
>loose
>the heat. To quote a well respected member of this list, "goose poop". That
>explanation implies that heat has inertia, and we know that it doesn't.
>The tip
>that slowing the water flow is pervasive enough that there must be some
>truth to
>it, only the explanation is incorrect. Can anyone shed some light on this
>from a
>physics point of view??
>If you don't want to re-kindle an old argument, feel free to e-mail me direct.
>
>Baffled in San Diego (although me water pump isn't),
>
>Craig Wright
>
>
>Bob Palmer wrote:
>
> > Armand,
> >
> > I took a quick look at this link. These guys aren't quite as extreme in the
> > B.S. as Edelbrock and the other higher price aftermarket water pump guys we
> > discussed a couple of years ago - but they don't charge quite as much
> > either. Too bad they don't show a picture of the impeller design; at least
> > I didn't see one. Is it stamped sheet metal or a fancy shaped cast one? I'd
> > stick with a Ford Motorsports HiPo or similar (like the one McCleod has).
> > But then, you already know what I think about this subject. ;-) Or we can
> > take Chris' advice and just loosen the old fan belt a little.
> >
> > Bob
Robert L. Palmer
UCSD, Dept. of AMES
619-822-1037 (o)
760-599-9927 (h)
rpalmer@ucsd.edu
rpalmer@cts.com
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