Hey Im a newbie. My motor is being built right now at Keith Craft, its a 408. I have a Radix that I am putting on it. I was wonding if anybody new what the smallest pulley is that I can put on the blower. I want to max it out. I talk to Magnacharger and they said the blowers max RPMs it can turn is 14,000. The rest of the pulleys on the truck are stock. Can anyone on here help me figure that out.

 

You need to know the crank pulley size exactly. You also need to know how high you are going to be winding your motor. Then you can calculate Radix RPM's based on different Radix pulley sizes:

Crank Pulley
----------- X Engine RPM = Radix RPM
Radix Pulley

 

How fast do you plan on spinning the motor?

 

Well does anyone know what size the stock on is? Because I do know that it is a stock crank pulley. With my calculations right now with a 3.0 pulley im already over spinning the blower as it is. Im not too sure on this one im having a brain fart today.

 

stock crank pulley is 7.5"

 

7.5 (crank pulley) * RPM / Radix pulley = Radix RPM.

 

Well if my formula's off, so is yours. It's the same formula.

 

Comes out the same. I guess that explains my good grades in algebra.

 

Just checked the pulley that came with my Radix = 3.1". With the stock redline of 5800 RPM that would calculate to 14,032 Radix rpm, but the new motor will turn 6200 which calculates to 15000 at the Radix.

Is the 14,000 max for thermal efficiency (intake air temps) or unit failure protection?

 

Also, I don't know what volume the Radix will deliver, but it seems like that will be the restriction for your 408...not enough volume.