I am thinking about having a larger crank pulley made to up the boost a tad bit more on the Whipple. I know that every 1/8 inch on the blower pulley is approx 1 pound of boost. How can I determine what change in size of the crank pulley will change boost to? I know this would overspin my accessories, but I dont plan to go real big, would like to get about another 2 psi out of it.

 

You can figure it out with a little math. It's a matter of change in surface area on the pulley (circumferance). diameter x 3.14159 = circumferance. You can use that by knowing your constant which is 1/8" diameter for 1lb boost approx. That will get you in the ball park... considering the "constant" isn't perfecty known.

 

Isn't that going to be a little pricy? I see the benifits vs a smaller blower pulley though.

 

I just 5min ago ordered one from ASP. But, mine is not the same as yours. I have the 2 pulley setup so what I'm getting is the pulley that bolts to the harmonic balancer(crank pulley). $250 plus shipping.

I thought you were't supposed to use a larger harmonic balancer on the 1 pulley setup? something about it being hooked to the alternator etc. Maybe I'm wrong.

 

Yep, the problem is you will overspin all your accesories, the alternator,water pump and power steering. The alternator would not be a problem, could easily get a larger pulley for it. Water pump and power steering pulley would probably be a different story though. It would shorten thier life span some, but not sure how much. I just wish I could figure out how much bigger the crank pulley would have to be for 2 more punds of boost. I suck at math

 

1/8" equals 1 lb, according to a post above. So it appears that 2 lb of boost would require 1/4" larger pulley crank pulley or smaller blower pulley. I'm confused. Why not go with a smaller supercharger pulley instead of a bigger crank pulley and then not have the other stuff overspun?

 

You can only go SO small with the blower pulley. For example, mine is 2.75" Whipple doesn't make a smaller one. I could have a smaller one made, but, the belt would slip like a **** no doubt. Going with a larger crank pulley, i'm hoping to get another 2lbs of boost by adding 1" diameter. No idea how to do the math, just going by what another board member said he did. I know on the 2 belt setup like mine, there's not alot of belt wrap at the blower pulley. That's just asking for it to slip. Poor design.

 

something else to consider is that your accessories (including the SC) will eat up more hp ... but consider getting under drive pullies for the accessories that ranwalk talked about to make them spin at the right rpm.
Good luck.

 

On my setup, this doesn't apply. My accessories all run off my stock harmonic balancer. The only thing I am changing is the pulley that bolts onto it (crank pulley). It is being made to be the same diameter as the balancer. When installed, it will look like i have a balancer that's twice as wide as it should be.