I was asked to start a thread here to discuss my planned use of an M90 supercharger on a Pontiac 4 cylinder I'm building. I'm building another car (3 year project) so this 4 cylinder is a side job.
For those not familiar with the early (1961-1963) Pontiac 4 cylinder, Pontiac cast a 389 V8 for their big cars. When they came out with the then compact sized Tempest LeMans smaller sedans/coupes, they needed a good solid 4 cylinder to power them. To cut costs they decided to cast a "half" 389 block with one bank (drivers side) missing. Much like the modern day modular Ford motors, they made it on the existing 389 tooling/line and it used many of the same parts from the everyday 389. Rods and pistons were interchangeable, bearings all interchanged, they did cast a smaller port head but it was the same architecture. They had to make a special 180 degree cast crank.
I've always wanted to build one for shnits and googles. I have a friend in Connecticut that built one with a turbo that is now over 600 hp at the crank. Not sure the pis but around 20. He is now trying to build it to live comfortably at 30 psi.
I want to build it for a comfortable 600 HP for full street duty. But use a supercharger instead. I'm going to start with a ported M90.
I want the supercharger so it can build boost right off of idle. A turbo would be the total HP choice but the 4 cylinder, with the head flow and camming to get to my goal, would be very week down low. I want the */c to help down there. The final choice of car to put it in will also affect
I also understand that the M90 may never flow well enough to hit my HP goal. So if the first phase with the M90 proves that it is capable of producing a lot of power and still be tractable for an everyday driver, I may move up to a bigger centrifugal. Or a turbo if it should be tractable down low without any help off boost. I've also thought about compound supercharging. Using a larger turbo to blow thru the M90.
I plan to make an aluminum plate to mount the blower to. Looking at a pic of the 4 cylinder, you can see the side of the block that was cast closed. There are several bolt bosses cast in. You ca also see the half tunnel ram intake that will get boxed in for a plenum and one throttle body or two smaller throttle bodies added in.
I'll make the plate with slotted mounting holes so I can move the plate/supercharger in and out (towards or away) from the block for belt tensioning purposes. The plate will have a opening in the bottom that matches the blower outlet opening. I'll weld an aluminum box to the bottom with a 2.5 or 3 inch tubing outlet. UNLESS, I can mount the blower upside down and not affect the oiling of the front gears. The reason being, mounting it right side up just means I have to run tubing back up and around the blower to an air to water intercooler, which will then feed a throttle body. If I can mount the blower upside down I can run it directly into an intercooler. Making it a single unit.
Right now I want to spend some time porting the blower. Designing and making the blower mounting pale and designing the sliding attachment brackets/mounts to work with whatever bosses I decide to use. A lot will depend on actual final pulley locations at the front of the crank.
Let me know about any and all mods to increase the efficiency/air flow of the M90. All info is welcome. I have been on U tube looking at all the mod vids and trying to see how much they affect performance. I also belong tot he Bonneville club as I used to own a 2002 SSEi until a freak hail storm completely totaled it.
Thanks for checking in and for any help. It is much appreciated.
(Oh, and you can tell me I'm nuts too, you won't be the first, LOL)