So I was reading on here that stage 2 pulley is 77.9? Is this correct? Ok any way I bought the car was told it's a stage 2 gm car so I open hood I have the blue bolts.... in my glove box I have the 77.9mm pulley and bit.... on the supercharger the pulley is not labeled stamped or anything? What how who?? Thanks.... any insight is appreciated....

 

the previous owner probably got stage 2 installed (tune, injectors, belt, smaller pulley, etc.) but then dropped pulley sizes.

It was quite common back in the day... a lot of people were running 2.8-2.9" pulleys with GM stage 2. Im guessing he bought a smaller pulley with no label so if he went in for warranty work they wouldn't question it.

How much boost you running? Other mods? Is your redline 6.5k rpm or 7k rpm?

 

Put that pulley up against the other under the hood keep the smaller of the two

 

OK I'll check them next to each other... and I think it's 6.5 I'm not sure I'll check tomorrow and as far as boost I believe 18 ish or more according to the Guage. I'll also check that tomorrow. I haven't been driving it as much because I ride a rocket most year round my girl drives the car.... but thanks for replies I'll let you know more tomorrow

 

The pulley in the supercharger is smaller than the 77.9 for sure. So.... other stuff TBD....

 

Check the inside of the smaller pulley where it connects to the hub.

Smoothflow (aftermarket pulley maker) puts the pulley size in there.