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Here is an article I wrote on cooling a while back. Much of this info has
been posted before and it is long so press delete if you get tired of
reading.
Since cooling is always a problem I have spent some time asking questions
of all who could give advice on the Tiger's eternal problem of over heating
To D.C. who has had more sports cars with overheating problems than any one
I have ever met. He has become our Club expert on over heating
Q. What is the "Magic Bullet" that I can bolt on and cure all my over
heating problems?
A. There is no such thing. The war on over heating is won little by
little, one degree at time.
To the College Automotive Department Head:
Q. Why do our engines over heat after rebuilding and an overbore of 30
thou +?
A. The closer the kettle is to the fire, the sooner the water will boil.
If you overbore you need to cool more.
New engines are tight. Tight is hot. Break 'em in at night.
To the Physics department:
Q. What fan blade works the best?
A. Try an asymmetrical fan. Symmetrical fan blades set up a vortex
(whirlpool of air) that is relatively stable. They move lots of air but
they tend to draw the air from only one spot just like the whirlpool of
water when you drain your bathtub. An asymmetrical fan tends to set up
an unstable vortex that moves around, drawing air from all over the
rad. The whirlpool of air from the symmetrical fan will be noisier too,
just like a cyclone. The unstable vortex from a asymmetrical fan will
not howl as the whirl pool is continually being changed.
TIP: Try a 140 series Volvo 5 blade, it bolts up to the Tiger engine and
requires no trimming. I have one on my car and it works great. I got
it for $3.00 at "Pick-Your-Part". Get the Volvo aluminum spacer. You
will have to have it turned down but it fits.
Q. What do you consider the single greatest cause of over heating?
A. Rads that are plugged. Excess silicon, (widely used in engine
rebuilding) tends to flake off in specs and block of the veins in the
rad. If a rad has 20 veins and you lose only 4 you loose 20% of your
cooling. If it worked proportionally 190
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=B0 + 20% =3D 228=B0.
TIP: Pull the rad and have it boiled. Flushing does nothing.
To an old time Rad man: who "fixes and doesn't just replace "
Q. What else can cause over heating?
A. Stoppage of air flow. Bent fins in the rad. If only one or two s=
mall
areas are blocked from air flow the result can be one or two degree=
s of
over heating. (Remember how we win this war - one degree at a ti=
me).
Get a small thin screwdriver and straighten every fin. Don't forget=
the
back side. Even a brand new core can have some damaged fins. Rad=
men
now-a-days don't like to take the time to do this but it helps.
Also . . . An old rad can have much of the air flow stopped by bit=
s of
sand stuck in the fins. This can be removed but plan to spend the =
week
end with a fine wire hook and use care. Boiling will not get ri=
d of
this sand, so if it's bad it may be time for a new core. And reme=
mber
airflow.
TIP: Bugs on the rad stop air. Use a rad screen clean it often
To a College Air Conditioning Technology Professor:
Q. What about air flow and how does it relate to cooling.
A. Now you are asking the right questions. Air flow is everything.=
Air
removes heat. Moving air removes more heat. (Ask us Canadians. M=
inus
40=B0 can be a pleasant day if there is no wind but at minus 20 wit=
h a 10
M.P.H. wind, flesh will freeze in 3 minutes.)
Q. So how does a fan move air in the cooling system of a car?
A. Very poorly. The designs were a bit hit and miss - mostly miss=
. We
would never get away with designs like that in the Air Con trade=
but
then we do not have the space restrictions. Especially older cars =
have
poor designs. Look at some of the new cars, where they want to =
save
weight by cutting back on the rad size. The engineers compensate=
for
this by proper shrouding.
Try This: Hold your hand up to your mouth and blow through your f=
ist.
You can feel the air with your other hand even 6 to 8 inches away.=
Now
suck. You can not feel the air move until you almost seal your fis=
t up
tight with your other hand. A car's cooling system is the same. The=
fan
sucks, or draws, the air through the rad. If you look at your Tig=
er's
rad shroud you will see that it is open at the bottom. No seal to =
help
the fan suck the air through the rad. Air does not like to go thr=
ough
things - It would rather go around and hence the "reverse" air =
flow
into the engine compartment. The air is being pulled from under the=
rad
and up through the fan. Shrouding the bottom of the engine compart=
ment
will work, to a degree, but it would be much more efficient to bui=
ld a
proper rad shroud, allowing the air to be drawn through the rad=
and
then exit, out the bottom, as it should.
An electric fan works because it blows through the rad but to re=
ally
work it should be shrouded to about one or two feet in front of=
the
rad. Not practical.
Q. What is the proper shroud then for a drawing fan?
A. A proper shroud is one that is sealed up all around the rad. A ru=
bber
gasket, between the shroud and the rad, would even help. No leaks.=
The
shroud should surround the fan completely. The fan should be ho=
used
with only 2/3 of the blades inside of the shroud. The air must be =
free
to fly away from the tips of the fan blade. This will give you air =
flow
at idle or at any speed.
To an Ex Rootes Automotive Engineer:
Q. Why were automotive cooling systems so poorly designed?
A. Money. Profit in automotive engineering is gained penny at a time, =
just
as you say cooling is achieved one degree at a time. We used to de=
sign
a rad that would cool an engine anywhere. Then, when the protot=
ypes
were being tested, we cut the rad back until it just worked then a=
dded
a bit. Every inch of rad core or shroud material saved was more pro=
fit.
Automotive design is one of cost cutting, not one of engineering de=
sign
excellence. If we had managed to cut the cost of the Tiger coo=
ling
system by $10 that would have made a profit of $70,000 more during =
it's
production run. The same $10 cut from the Mustang may have been w=
orth
perhaps $20,000,000 to Ford during the car's production life.
Remember the warrantee for most cars back then was 12 months or 12=
,000
miles. We never designed them to last for 200 to 300,000 miles an=
d 25
years. Modern cars are different. Longer warrantees necessitate be=
tter
engineering and plastics now allow you to design a good shroud a=
t no
more cost or weight than a poor one. It was different when metal=
and
hand labor was used for every shroud built.
We did smoke tests on air flow and when a car is sitting at idle=
the
air is pulled through the rad by the fan, it then hits the pave=
ment
under the car and much of it is drawn forward, back up through the=
rad
again thus trying to cool with pre-heated air. Shrouds in front of=
the
rad, at the bottom, did stop this on some cars but I am not sur=
e it
would work on the Tiger. I can't remember specifically working on t=
hem.
=
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