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           Cushman/Vanguard Conversion Technical Details





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This is the conversion information for the Red Silver Eagle 
chassis shown in the pictures. The conversion of the Silver 
Cast Iron chassis is similar except that it has a 18 HP engine.

My conversion uses the Briggs & Stratton Vanguard 16 HP
engine. The Vanguard is their premium line and is used in
industrial equipment and in $10K class lawn mowers such as
the Grasshopper. Also available are model of 18, 20, and up
to 25 HP.  It is made in Japan and looks a lot like a Honda.
Any Briggs & Stratton Authorized Racing Dealer can hop
up the 18 or 20 HP models to in the 40HP range. For more
information see the  Briggs & Stratton Internet site on racing.

The conversion also uses the Comet model 40 series torque
converter which has a ratio of 2.43:1 at low speed, decreasing
to 1:1 at high speed. The Comet keeps the engine at the top
of it's maximum torque curve for maximum acceleration.
Comet makes these converters for both two and four cycle
engines. For four cycle engines engagement speeds from 1600
to 3100 are available. This one uses 1600 RPM which seems to
be just right. The rear end ratio is 2.5:1 (24T to 60T). It goes
from 0 to 50 in 12.8 seconds. I have gone it as fast as 68 MPH
and it still had a little left. Cruses just fine at 60 with no strain
no pain (and absolutely no vibration) at about 3200 RPM. Mph's
verified with a GPS unit. Cushman speedometers are not very

The original air cleaner cannot be used and a new one must
be fabricated.  This one uses a flat pancake style that
closely matches the original. The Vanguard engine uses a
form of supercharging by routing some of the pressurized air
from the shroud back into the air cleaner. Some conversions
have omitted this feature and the engine still runs fine but
it may loose a little power.  Most Vanguards use a fuel pump.
It is not necessary with an overhead gas tank but Briggs says
a carburetor jet change is required if it is omitted. I used it
but relocated it down between the V cylinders to get it out
of sight. Some ingenuity is required to couple the Vanguard
carburetor to the throttle cable. The Vanguard carburetor
pushes for maximum RPM and has to be reversed with a
bell crank or similar means for a standard throttle setup. A
jack shaft is used to transfer power from the Comet driven
pulley across to the drive sprocket. The spacing between the
Comet driver and driven pulleys and the offset of the two pulleys
is very critical. Several different length belts are available to
give some flexibility in designing a system.  Note how loose
the belt appears at idle. The belt is 7/8 inches wide and is
made of Mylar. This conversion is on a Silver Eagle chassis.
I have also completed a conversion on a Cast Iron 1959
Eagle and may include it in this web site in the near
future. The complete kit for the Cast Iron version can be
obtained from Elbert Faris at (561) 794-4559. If you are
going to convert a Silver Eagle you can obtain  many of
the parts from Elbert.    

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