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My Fellow Spridgeteers,
This comes from the Judson Supercharger list and I'm sure you'll find it
most interesting, whether or not you currently own a Judson. Haddon (W.
Haddon Judson) is quite active and in the process of developing new,
related web sites.
Before reading Haddon's response, you might want to read John's original
post below.
WFO Herb
Keep the sticky side down!
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for judson-actors; Thu, 12 Oct 2000 09:41:35 -0600 (MDT)
From "GulphMills.Com" <judson at gulphmills.com>
To: <BANJOJOHN@aol.com>, <judson@autox.team.net>
Subject: RE: questions for Haddon Judson
Date: Thu, 12 Oct 2000 11:48:25 -0700
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Hello John,
All Judson superchargers, in that time period, where designed for a specific
engine displacement. While there is some room to "boost up" an engine with
a greater CID than the supercharger was designed for. This tolerance is not
that great. Engines built before the 1972/1973 era where generally long
stroke and produced their maximum power between 2800/3000 RPM to 3900/4100
RPM. The Judson supercharger was designed with this power curve in mind.
The commercially available Judson superchargers where designed to run at a
constant speed of 5800 RPM(with water cooling jacket installed) and higher
shaft speeds intermittently. In reality the usual running speed of the
supercharger was well below 5500 RPM. The rotor was balanced on a Gisholt
Balancer to a tolerance of 1/25 millionth of an inch at a speed of 6000 RPM.
The balancing procedure did not place any stress on the rotor so the
balancing speed of 6000 RPM had no effect. In use though running the
supercharger at 8675 RPM would not be advisable. The original bearings were
from the New Departure Bearing unit of General Motors and were not designed
to run at 8675 RPM. If you are going to run the blower at high speeds
change the bearings to taper rather the ball and wrap 1 inch copper tubing
into the groves(silver soldered on) on the blower housing, inline with a
heater cooling core and connected to you radiator/cooling system. I do not
recommend you running the blower at high speeds.
The supercharger you have was designed for a 1 litre engine. Actual range
was 925cc to 1000cc. We used to run the sprite blower on 850cc Austin
engines...they hauled!!
As far as porting and polishing the interiors) of the manifolds try it.
Port and polish the interior and then lightly sand blast the interior...this
will give the fluids a laminar flow pattern which should help the charge
enter the cylinder smoother. One of the functions of a supercharger is to
completely homogenize the fuel/air mixture so the there are no lean or rich
areas in the cylinder when the plug fires. Porting and polishing help keep
the mixture homogenized. If you are going to run the blower on the 1275
engine you might want to use SU H4 carbs or Strombergs. The stock carbs on
the Volvo B16B engine should work. You will have to change the jet and
piston/needle assembly to reduce fuel consumption.
Thanks, Haddon
-----Original Message-----
From owner-judson at autox.team.net [mailto:owner-judson@autox.team.net]On
Behalf Of BANJOJOHN@aol.com
Sent: Thursday, October 12, 2000 1:24 AM
To: judson@autox.team.net
Subject: questions for Haddon Judson
Hi Haddon:
Since I know you monitor this list, I'm asking your expert opinion on the
use
of the Judson SC designed for the 948 Sprite/midget engine on a 1275. What
modifications would you make? The most obvious is, of course, would you
change the pulley ratio to 1:1.735 vs. 1.29 to compensate for the
displacement difference?
By my calculations that would generate a 8675 rpm Judson speed at 5000 rpm
engine speed. What is the estimated red line for the judson? Can it take
that kind of abuse?
Can the manifold ports be bored out to 1.25" to match the intake ports on
the
head to give less restriction to the flow of the fuel/air mixture?
would you modify anything at the carburator end to accomodate the higher air
volume needed? different air filter setup, different carb.,etc.?
Not trying to re-engineer it, just trying to maximize the benefit on a
larger
engine.
TIA
John O'Brien
'61 bugeye
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