Once you’ve sourced an M90, the next step is rebuilding it. For better or worse, most of the motors paired with the M90 were fantastically durable, which means high miles on the blower. At the very least, the snout should be rebuilt. While there are different lengths available depending on the original application, they all use the same seals, bearings, and coupler, which are the snout parts that should be replaced. I’ll frequently reference the photo above, which comes from an ongoing project by user NVA-AV6 at V6Performance.net, and there’s a high-resolution version for easier viewing.
First, remove the pulley from the ‘charger with care. The suckers are really on there, thanks to an M12 lock nut and high-interference press fit, and I damaged the stock pulley when removing it with garden-variety three-prong gear puller. A steel backing plate for the puller to grab will protect the pulley, as will a more expensive but perfectly-suited supercharger pulley remover. The snout itself is the tall aluminum casting on the far right, which mates with the supercharger body via some odd M6 bolts. Some of them have very tall studs for wiring harness mounts sticking out of the head — tall enough that some deep sockets may not be enough, but a 10mm box-end wrench should fit.
When the pulley and snout are off, you’ll be able to see the coupler, which is the gray plastic part between the supercharger housing and pulley nut in the photo above. As you can see, it’s a sort of lovejoy coupling with three fingers from each side joining in a hex pattern at the coupler. Normally, these are deformed, and the photo’s coupler is an aftermarket part. Stock versions may have a beige plastic coupler with two springs inside, designed to absorb vibrations from the accessory drive system. Mine had a stock coupler, which was cracked in three places and dangerously close to falling apart. Aftermarket solid couplers are much stronger, but a bit tougher on the supercharger.