to all those running small pulleys on ur comptechs.... how tight do u guys tighten ur belt to insure no slippage occurs? i know mustang guys just torque them down as tight as possible, but i knew someone who did this on his ctsc and the belt snapped.....

and do u guys have to change ur belts more often then when u we're running the stock pulleys?

 

Gah...I don't think you want to tighten it as much as possible. Belts snapping and pulleys breaking could be the result.

The rule of thumb is when you cannot finger twist the belt 90 degrees at a point halfway on the non-tension pulley side. Maybe give it a couple of more slight tightens after that, but don't crank down on it.

 

i agree, i'm actually more worried about the supercharger's bearings than the belt or pulley.

 

A while back someone with either a VT or CTSC said that he had overtorqued the tensioner and that, as a result, his supercharger bearings had failed. He ended up rebuilding (I think).

This was a couple years ago, I think. But yeah, the rule of thumb is that you shouldn't be able to twist the belt much more than 45*.

 

When I went up the boost this summer, we ran into that issue. The rule of testing the 45 degrees belt twist did not work well for the 11psi pulley. On the dyno, my car couldn't break 8-9 psi depending on if the engine was hot or cold. So then the tuner tighten it as much as he could within reason, I tested the belt twist, and I could still bend it a little bit, but not even close to 45 degrees.

Put the car back on the dyno, and the car hit 11psi on the dot at red line.

 

I just took a look at my setup (3.6" SOS pulley) and I'm gonna agree. I don't think I get more than 30* of deflection and I'm at 10psi. So maybe we should revisit that theory.

I guess the better rule of thumb would be to tighten the tensioner the minimum amount it takes to get full boost at redline. Unfortunately, if you're on a dyno...the tuner's not going to like experimenting with something so mundane.

 

My 3.0" pulley gave 8.5psi without any tightening. It was tough just to slip the belt on.

Got up to 12.xpsi after tightening it down. I added a second bolt/washer combo above the original, to help prevent loosening. My mount is fairly worn though.

 

At a recent Mase dyno day a couple of us had exactly the same problem with the blet slipping afte tightening it to the 45*.
One jack lever later and they were on full boost and very little deflection.