supercharger

[Tim Keith]

What are strong weak points of the supercharger from a '94 Buick 3800 V6? Are they difficult to rebuild? I don't have a Buick. Looks like it could be adapted to another motor. Is it a good design that can easily be serviced without sending to a special repair shop?

[CNC-Dude]

There cheap and easy to find. Its matched pretty closely to the slant engine for sizing, since the Buick is a 231 cubic inch. They also work good and can be adapted to other engines easily with just a minumum of mechanical ability.

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There's no such thing as too much cam....only not enough engine!

[Tim Keith]

I found it as a U-pull-it on the returns shelf, suggesting that it
needs a repair. I found bearing kits for a reasonable price.
The price at the U-Pull is $150. The shaft turns smoothly but
I think worn units only make noise under load.

It would work good on a slant. I am rebuilding a Datsun L20-B four
cylinder motor. The snout length looks about the right for a four.
The Datsun L-series has a robust fully-counter weighted forged
crankshaft that is balanced well enough that the motor does not
need a harmonic balancer. I was thinking of converting the 110 HP
motor into 150 HP with a little boost. The L20B block can handle
more than 4 times that much power. I have two Datsun 620 trucks
with the L20B. I think one might get a 20 year old KA24DE as that
old school dual cam motor already makes 155 HP with no variable
valve timing, nothing but the basics.

Just wondering what the DIY repair costs might be for the
Roots supercharger, which I think is an Eaton. I think the snout
would work better for a four, although I suppose there are kits
to replace the snout.

[Ceej]

The GM Eaton has a couple things to check out.

First, you can not draw through it. The rotor coatings can not be exposed to fuel. They will fail, and the coating will go into your engine.

Second, the most common wear part is the plastic coupler that times the rotors. They are about $10, and can be replaced easily. The bearings are life time, as long as you keep the right oil in them.

If the blower has been stored nose down, the oil will leak out through the input shaft seal. This is normal. The seal isn't bad. Get the appropriate oil for it.

The bypass valve is only open when the blower is being turned at low rpm, and there is vacuum in the intake. It bypasses the blower. As soon as the blower spins up, the valve will shut as vacuum goes away, and the blower will start flowing air. This butterfly valve is not used as a pop-off/waste gate type of device. If there is any pressure in the intake, this valve will not open. It is common to lock it closed, and rely on a pop-off valve in a performance application.

The Eaton is not a compressor like a detroit. The only "Boost" you will see is when the air "Stacks up" in the intake. It is not common to see high boost levels with this blower.

You will need a backfire plate. You can not use this configuration with a blow through easily. Whatever air is allowed into the front of the blower will be pushed into the intake. When you suddenly close the throttle, it can bend the throttle plates so a popoff must be used. The way this unit is designed, you close off the throttle body plates in front of the rotors. While a pop-off can be used, it isn't commonly done.

The rotors can be re-coated, but generally that doesn't need to be done unless fuel has desolved it. The rotors run with zero tolerance, so seal very well. They will show wear marks, as the coating self clearances when you run it for the first time.

This part is too long with the GM snout on it. Snouts are offered that are much shorter. I looked at a 4" snout. The throttle body will still be right about where your Master Cylinder is located.

Fortunately, you can run the blower at virtually any angle. It can blow up, sideways, or down. The blower doesn't care.

The Eaton for the Ford is much more compact. The throttle body is not in line with the back of the housing, and sticks out to the side.

I don't remember when the cut off was, but the early GM was the M-62, and the late one was the M-90. The later ones are much more efficient than the early units.

2¢

CJ

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Tyrde-Browne Racing

I'm off to find myself. If I should return before I get back, keep me here.

[kesteb]

GM switched to the M90 around '95-'96. Tim would have a M62 which should be fine for the Nissan motor.

Ceej is right, the GM M90 puts the throttle body right next to the master cylinder on a A-Body. It is so close that it won't work in a '65 with dual Dutras. I doubt you could use power brakes in any A-Body. Nor can you turn the throttle body without hitting either the master cylinder, the hood or your new fuel rail. The only way to use the GM M90 is probably using a jack shaft and face the throttle body to the front of the engine.