There is only one crank pulley dia available as far as something that bolts on, I am running the 12 rib wide pulleys and unless I go bigger on the supercharger any bigger upper pulley will obviously lower my boost. I have fought boost problems for quite a while, tried a plunger type tensioner like bigger m-5s use and it didn't work out, put a new tensioner on and it seemed like it fixed the problems, but already seeing a drop in boost when running boat hot so going to do something as its pizzing me off now. I can index a pulley a run a mill cutter thru it and do what Reichard is doing but there is some debate as to weather it will shred belts every ride, I am probably going to send my 3.85 and 4.0 pulleys out for the Carbonite coating, send my 3.70 pulley out to be coated THEN punch the holes in it to add grip, Smitty

Have u tried two six rib belts? I know guys that swear by it...

I tried that 2 years ago and it would shred edges of them BUT at the time my tensioner was allowing misalignment, maybe will try that again!

Why so against a cog set up< seems like a great solution.

Belt wrap.

I was looking at pictures of a blower set up yesterday, and the wrap on the blower pulley was appx. 100 degrees. Not nearly enough. We ran some where the belt almost touched.

I never ran an M3, but we did see the factory brackets on the 4s and 5s flexing and causing the belt to slip. I saw it on the dyno, boost would just fall off and the ribs were gone from the belt. Back pressure from small cams, intakes and throttle bodies makes them harder to turn, not saying that's your problem. When the rear throttle plates flipped upside down on my throttle bodies I was fueling for 1800hp and only seeing 1400, that took the ribs off also.

In talking with guys who run them they tell me that IF the head bracket flexes or anything isn't perfect they fling belts off and when they work they work good but they have short life span plus triple the cost of the serpentine belts which are already too exspensive and also told that adding a blowoff valve is a must when going cogged, my boat takes a lot of time to get a new belt on because the rear seat is close to pulley so I would like to get a belt to grip and last. Going to do something with the pulleys, probably the carbonite deal, will post pics and results IF I do, Smitty

I'm turning my supercharger about 58,000-60,000 rpms and its only rated to turn 50,000 so I have no doubt its under a little load!! Had Randy Fedo /CNC look at making beefier bracket, all kinda problems need to be solved that that would create so I never got far with it, going to get pulleys coated and see what that does, Smitty

I turn them up a bit myself, can you run a brace back to the intake manifold.

I have looked at it before and tried to figure out where I could squeeze one in, I AM going to take a look at it one more time this year before hot boat weekend in Sept in a different light now that I own 2 mills and lathes and can whittle stuff out, I think even a couple of ribs on back of plate might do something!