V1 GM Stage 2 Pulley

[Robinjo]

I just pulled my GM Stage 2 pulley and installed the ZZP modular kit. The ZZP is 3.0” but measuring my old pulley I get 70 mm which would be 2.789 (~2.8”). Am I measuring wrong? I thought GM Stage 2 was 3.05”.

 

[Gtstorey]

If that is a GM pulley, I would expect it to have a GM part number on it somewhere.

 

[Robinjo]

If that is a GM pulley, I would expect it to have a GM part number on it somewhere.

I didn’t see one but I’ll look closer. I was actually looking for a pulley size but couldn’t find one.
I’ve measured multiple ways and keep coming up with the same 70mm number.

 

[Rttoys]

This is the GM pulley I had. One way screws. GM programming, that I know of.

 

[Robinjo]

Just confirmed that there is no marking on my pulley. Also, It has torsion bolts instead of the blue GM star (anti-tamper) bolts. Looks like I had a smaller 70-71mm pulley than the GM S2 77.9mm for some reason.

That explains why my Stage 2 serpentine belt was hell to get back on that 3.0" pulley.

 

[Gtstorey]

Have you compared your tune to a GM stage 2?

 

[Gtstorey]

And lack of part number isn’t 100% but GM is pretty thorough at including it.

 

[Robinjo]

Have you compared your tune to a GM stage 2?

I have not. Great idea for something to look into. Since my pulley looks nothing like Rttoys I'm not so sure it was a GM S2 now, that is just what the guy I bought the donor from told me. There will be a bit more investigating into this. If the streets clear up a bit I'm going to see how the 3.0" pulley feels, maybe just an easy ride down the mountain and back up. When I started it last night and let it idle the AFR read 14.5-14.8.

 

[Gtstorey]

Around idle shouldn’t change much. It will be more when it gets into the upper level of boost that will be different. And I don’t know how your PE is defined. Maybe Boost and RPM? And you VE table may need to be extended. But I’m just guessing.

 

[Robinjo]

Looks like I need to finally attach that A/C wire to my wideband and set up the function in HPT to log it.