COOLING FAN UPGRADE
                          By Ben Prince

    For a number of years, my wife and I lived in Richland, one
of the hottest spots in eastern Washington.  Summertime
temperatures routinely exceed one hundred degrees, and for a few
days each year, 110 degrees is not unusual.
           
     In this environment, the cooling system in our TF was
nothing to shout about.  The worst situation occurred when idling
at stop lights in heavy traffic, the temperature needle creeping
uncomfortably high.
           
     The problem was not unique to the TF since two acquaintances
with TDs had similar difficulties.  The situation is perhaps
exacerbated with the TF, since the TF radiator capacity is about
one quart less than the TD.  On the other hand, the TD system is
unpressurized in contrast to the pressurized TF, so perhaps the
TD and TF are somewhat equivalent (equally bad).

     When I first encountered cooling trouble, I contacted Carl
Cederstrand and Jerry Felper, technical gurus from the Vintage MG
Club of Southern California.  I figured that individuals who
routinely drive old MGs in the Los Angeles area would have some
good ideas on what to do for cooling.  And indeed they did.

     Aside from making certain that the existing cooling system
was in working order (water pump functioning, cooling passages
clear, proper radiator flow, etc.), installing an effective fan
was an item near the top of their list.  They pointed out that
the stock fan is quite inefficient.  Several years ago, Carl
added a couple of blades to his original TD fan, changing it to
six blades and improving its operation.  Jerry suggested that
other options are available today, stating that some Datsun,
Mitsubishi and Dodge Colt fans have the right hole spacing.  He
also mentioned that an MGB fan would work.  He indicated that
these later model fans are aerodynamically superior compared to
the original setup.

     I spent a bit of time looking in junk yards, but never did
find a Datsun, Mitsubishi or Dodge fan that would fit.  I opted
for a new MGB fan -- the plastic one with seven blades (in
contrast to my original TF fan with only four blades).  The MGB
fan is listed in the Moss catalog as part number 434-340 and
sells for about $45.  I purchased mine from O'Connor Classic
Cars.
           
     The bolt spacing and cut-out for the new MGB fan were
properly positioned to allow direct installation in our TF.  The
bolt holes in the fan are about 9/32" in diameter, however, so
the fit is too sloppy if the original 5 mm bolts are to be used.  
One solution is to switch to 1/4" bolts by enlarging the holes in
the water pump flange, and tapping these holes for a common 1/4"
thread.
       
     A second approach is to insert sleeves into the fan holes to
take up the slack and allow the original bolts to be used.  I
decided to go this route, finding sleeves at Eagle Hardware that
were almost the right size except for the outside diameter which
was slightly too large.  I purchased them anyway, and had a
machine shop turn them to the proper diameter.  Perhaps a
specialty establishment, like Tacoma Screw, has the right size
sleeves, in which case the machine shop effort would be
unnecessary.

     Dale Drake had another solution for the large-bolt-hole-
problem when he installed a MGB fan in his TD.  He completely
removed the bushings from the MGB fan and had a machinist make
new ones.  These replacement bushings were turned to the proper
size to directly accommodate the original 5 mm bolts.

     The new MGB fan protrudes farther forward than the original.
This is generally desirable because the closer the fan to the
radiator, the better the cooling.  It is important, however, that
the fan not be so close that the radiator gets scraped.  
According to an after-market fan manufacturer, the forward most
spot on the front of the fan should be about 3/4" from the
radiator, and no closer than 1/2".

     If the MGB fan sticks too far forward on a TC, there is not
much that can be done to move it backward and make it function.
For the TD/TF, however, there is a spacer with the original fan
(Moss part number 434-070) that may be removed or cut shorter if
the MGB fan is too close to the radiator.  The best fit for our
TF was achieved by having a machinist shorten the spacer.

     If the TD/TF spacer is shortened or removed, shorter bolts
may be needed.  If you drill and tap the water pump flange for
standard 1/4" bolts, finding shorter ones is not difficult.  If
you instead decide to use the original size bolts (with sleeves
or new bushings in the fan), finding shorter bolts is a problem.  
This is because the original bolts are a 5 mm metric size with an
odd-ball .75 pitch.  (No, they are not Whitworth threads, and,
no, 5 mm metric bolts with .8 pitch from your local hardware
store will not fit.)  If you shorten the old spacer, then adding
washers under the original bolt heads is not pretty, but it will
work.  If the old spacer is completely removed, shorter bolts
that normally go with a TC fan will fit very nicely.  These TC
bolts are in the Moss and Abingdon Spares catalogs.
       
     One significant advantage of the new fan is its very light
weight -- 6 ounces compared to 19 ounces for the original.  The
lighter weight of the MGB fan with its better balance will be
much kinder to the water pump bearings.
           
     The only thing I didn't like about the new fan was its ugly
yellow color.  This was easily corrected by painting it black.  A
couple of coats of Hammerite spray paint worked quite well.
           
   

Page 2 of Cooling Fan