Started with a standard GM Series II 3800 M90 supercharger, gutted the case and started chopping. Got it cut down, then went to the stock shelf and started fitting stuff up.
All cut down on the back end, anyway. Getting things cleaned up and this made it VERY easy to do the intake side porting.
Now you can see how we're going to work this. Raising the inlet up and opening the bore from 65mm to 83mm.
Getting things sealed back up on the inlet side, all the intake porting is done, just need to run over things with a cartridge roll or two and clean up the burrs and divots from the carbides.
Much more direct path into the rotors, will be noisier but that's easily dealt with for 99c at the shooting store.
A few good shots of the porting, both inlet and outlet ports. It doesn't take much to push an M90 up to 600CFM inlet flow, but it does take some work to get one higher than about 650CFM...Stock this housing pushes 520-540CFM.
Not much to it, a little cleaning in the case and all those "score marks" wipe right out. they're not even deep enough to catch a fingernail, but the carbon and oil deposits make them look like someone went at the case with 36 grit paper!
Might try to find another rotor pack, as this one has some miles on it. They're not terribly hard to find and this one will work for a while yet. It's not leaking nose drive oil, so the front bearings are still tight enough to keep the seals from going to shit. I've rebuilt the rotor pack in my M62...it's a shit job unless you've got the special jigs to do it. I probably would be money ahead to pay the 500$ to have a rotor pack re-coated and rebuilt. However, good condition M90 rotor packs are all over and are far less money than a newly rebuilt one.
I still need to cut down the nose drive to the proper length, then it's two ball bearings, one snout seal, and two case bearings to replace. A new baseplate will have to be cut and I will be refining the method used to make the charge pipe, hopefully making it flow better than the current charge pipe and also lower profile...that way I can get it up off the lower radiator hose and alternator.