Lester,
The following is some detailed info that I had saved on my office computer
regarding the Judson. I can not vouch for it but you might find some usefull
stuff.
Mark Endicott
__________________________________________________________________
JUL97-11.doc
tech tips
1275 + Judson supercharger=horsepower
by
John Gronberg
This article deals with the installation of the Judson supercharger on a 1275
Sprite engine. Before I begin, I would like to direct your attention to an
article by Dean Hedin, "Judson Rebuild", printed in the Sprite newsletter
published by Rick Moses, Vol. 3 No. 3 Issue 11, dated July /Aug./ Sept. 1987.
The compression ratio of this supercharged engine is 8.0:1. The supercharger
kicks in under hard acceleration in 3rd or 4th gear, and the 1275 really
responds. The boost gauge which monitors all boost and vacuum in the intake
manifold will jump to a maximum of 2 lb. of boost under these conditions with
the pulley size detailed below. This means less down-shifting during in-town
driving and an automatic passing gear during highway cruising. Using normal
gasoline available, there is no pre-ignition. I suspect, however, that if I
increase the pulley size and boost pressure, I will begin to enter the danger
zone and will have to deal with pre-ignition. The Judson under normal
driving conditions does not have a high noise level, although during the
initial break-in period there was some clackety-clack, that has since
disappeared. The engine starts from cold with a minimum of choke; and after
a normal warm-up runs just fine. The Judson is a very simple design for a
automobile supercharger. Rebuilding one is not hard and most of the
components can be repaired or replaced with some research. The horsepower
increase to an engine of this type will range from 25% to 50%. I know of no
other single bolt on improvement that can match this efficiency.
Engine overall length, and wrong crankshaft pulley: The 1275 series is about
1/2 inch longer from the front of the engine block to the rear than the
smaller engines. While the Judson with its accompanying intake manifold will
bolt right up to the cylinder head, the supercharger pulley will not mate up
with the tandem pulley originally supplied with the Judson kit. This tandem
pulley was to be bolted in parallel with the smaller engine series crank shaft
pulley and drive the supercharger. The 1275 has a larger crankshaft pulley
that incorporates a harmonic balance feature to make the engine run smother.
Solution: The later 1275 engines used a smog pump for pollution control.
This pump was driven from a second pulley on the water pump pulley. I used
this pulley to match up to the Judson pulley. There was still the problem of
it being 1/2 inch shorter. This was taken care of by lengthening the Judson
pulley 1/2 inch, using a spacer behind the Judson pulley. This pulley
combination gives me about 2 lb. of boost. Because the pulley ratio is
somewhat lower than the original design I am not getting the maximum amount of
boost. By reducing the supercharger pulley to 3 inches will provide the
correct boost.
Hesitation off idle: The supercharger has a tendency to hesitate when cold. I
tried larger accelerator jets but nothing really fixed the problem. After the
car and supercharger warms up the problem goes away. The engine now starts
with a minimum amount of choke and runs fine after that.
Timing chain oil separator: The front engine oil separator will interfere with
the supercharger belt. To solve this problem, use a front timing chain cover
without the oil separator. Use the mechanical fuel pump cover to vent the
engine sump to the Sprite PVC valve and into the Judson intake manifold.
Vanes: Judson vanes have been a topic of some research. In Dean's article he
mentioned the use of Teflon vanes. While Teflon is the slipperiest material
known to man, in its purest form it is not very strong, and I agree with him,
this material is not strong enough to withstand the pressures inside the
supercharger. The Judson vanes I have been using are graphic loaded phonetic
parts. The graphite provides additional lubrication inside the supercharger
and the phonetic nature of this material has the necessary strength. The
housing was honed when I first rebuilt the unit and even after using the
Judson for the past years the inside surface of the housing is still not
scratched or marked at all. Dean mentioned he is using Delrin vanes. This
material should work just as well and is probably cheaper. The Holley
carburetor was not designed to work with the Sprite electrical fuel pump.
This pump provides too much pressure for the fuel input valve in the Holley.
I purchased a "Gross Jet" valve {3/91}and the problem disappeared. During my
11/97 Holley rebuild by Pony Carburetors they removed the Gross Jet and
replaced it with the standard needle valve and seat as originally supplied by
Holley.
Holley carburetor air cleaner: When I originally installed the Judson there
was no air cleaner for the Holley carburetor. I had an air cleaner bracket
machined at the local shop, but was never satisfied with the results. I found
an air cleaner and bracket from K&N model RU-0650 that works well and carries
a 100,000 mile warranty. I also had the Holley rebuilt by Pony Carburetors in
1997.
Oil injector: The oil injector purchased from Vaco has worked fine. I have
been using Castrol 2-cycle injector oil. This oil is designed to be used in
two-cycle motorcycle engines mixed with gasoline or directly injected into the
engine. I found it works fine as a Judson lubrication oil. The Vaco oilier
allows for some adjustment of the amount of oil injected into the engine. I
found that I could adjust it down until the oil stops flowing at idle then
back it out until you see it flowing through the Vaco valve sight glass.
Pressure Gauge: I have used a manifold pressure gage {VDO} since the initial
installation. At first the pressure would reach about 2 - 3 pounds of
pressure in 4th gear. However over the years the pressure has varied from 2
pounds down to 1 - 2 pounds. This has me wondering what is going on? It
would seem the vanes inside the housing are not making a good seal or they are
worn out. However looking at the vanes they look as good as the day I
installed them so I am still at a quandary why the pressure has dropped.
This does not seem to have changed the overall driving situation.
Accelerating through the gears the pressure jumps up to about 2 pounds in 4th
gear and really makes the car respond.
Other Useful information: The Holley main jet #42 works just fine. I increased
this jet to the #48 and the spark plugs were noticeably fuel fouled. You
must run with a PVC valve installed or oil leaks will develop. I originally
had the lower engine sump and the valve cover vented to the air. This caused
oil leaks that would not stop until I installed a PVC valve.
Final comments: I did have one major problem during last year. I tightened
the drive pulley too tight and the shaft spacer cut into the soft aluminum
rotor. This allowed the rotor to cut the side of the front rotor housing. I
investigated having the rotor machined so I could insert a bearing for the
spacer to ride against. However, the local machine shop wanted too much money
to fix it so I came up with the following repair. I took a steel washer and
had it turned down to fit into the indention caused by the spacer. To hold
the washer in place I used metal based epoxy. This combination has worked and
the spacer rides on the steel washer rather that the aluminum rotor. Leave
about one inch of play in the supercharger belt when adjusting the idler
pulley.
(John can be reached at john.gronberg@us.landisstaefa.com)
Addresses
Oil injection for Judson
Vaco Inc
Formally Ampco Inc. Lake St.
Florence, Mass
01060
413-586-0978
Holley Carb Parts
Holley (list #2042-5)
Replacement Parts Div.
Technical Service Dept.
601 Space park North
South Cartwrite St.
Goodlettsville, TN
37072
502-782-2900
Holley air cleaner
K&N Air Cleaners
561 Iowa Ave.
PO Box 1329
Riverside, CA 92502
800-858-3333
Holley Carb Rebuild
Pony Carburetors
PO box 420
Cazenovia,NY 13035
315-662-3003
Gross Jet
D&G Valve
8 MT Vernon St.
Stonebon, Mass
02180
781-438-1773
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