Hi, my dad has a 86 Trans Am that has a 383 with a D1SC Procharger on it. It currently has a 4.25" 8 rib pulley,and it pumps about 6-7 lbs. of boost. We are going to change the pulley to a 3.70" pulley to get the boost up to around 10-12 lbs. He called ATI today and they said that going from the 4.25" pulley to the 3.70" pulley would increase the boost around 5 lbs.,so that would put him in the 10-12 lb. range. I need to know what belt to buy for the new 3.70" pulley? We have had experience with the Prochargers in the past,and found out that a belt that is 1/2" shorter than ATI recommends gives more belt tensionor room. The crank pulley is a 7.65" TPI crank pulley.

Can someone give me a part# or belt length to run with the 3.70" pulley?

Thanks

 

I always went to the parts store and bought the next few sizes smaller and returned which ever ones I didn't need.

 

Damn wish it was that easy with a 12 rib

 

It's almost that easy. You just have to buy 2 6 rib belts.