[gt91]

I am looking at getting a smaller pulley for the A-trim blower, and am not sure which one I need.

Prior to changing the heads and intake, the A-trim was putting out just under 5psi with the stock 3.33 inch blower pulley and 6 inch crank pulley. Due to it being winter time, I have been able to run the car to see how much boost I am now getting, after swapping heads and intake.

I would now like to spin the blower up to 8psi and would like to know which pulley size would get me there.

The two pullies available are the 2.87 inch and the 2.62 inch. The 2.62 will slightly exceed the max blower rpm.

The old A-trim High Output kit used to claim an output of 8psi on a stock motor, using a 6.5inch crank pulley and a 3.33 blower pulley.

I am not sure, now that I have modified the motor, how fast I have to spin the blower in order to get the 8psi I'm after.

Does anyone have any experience with this ?

[dufkis]

A 3.125 pulley should do the trick.

[gt91]

Thanks for the reply.

Yeah, using a 3.12" with the 6" crank will get me almost the same ratio as using a 3.33" with a 6.5" crank, and therefore should produce 8psi on a stock motor according to original Vortech advertising for the a-trim high output kit.

I guess what I need to know is how much the boost will drop now that the heads and intake are modified, and are allowing more flow through the motor, and therefore how much faster the blower needs to be spun.

[dufkis]

2.87 would be the smallest I would go. You wont know your boost until you get the car out and test it. Each set up is different.

[gt91]

2.87 is what I was thinking of as well.

That size will keep the blower just under the max 45000rpms at 6000rpms on the engine.

It will also put the blower at 40000rpms at 5000 engine rpm, which according to Vortech is the max efficient blower speed.

Thanks for the help.