I'm having a custom 3" pulley made because Lysholm doesn't make them and Whipple pulleys are slightly different. Question is, what kind of boost is a 3" going to make over a 3.25"?

Second question, My truck hasn't been tuned for my meth system yet, only pump gas so I'm wondering if I was to throw the 3" pulley on and start spraying meth would that keep afr and timing under control until I have the tune redone?

 

My brother did that on his lysholm blower. It gained a solid 3# boost. He made 16-17 psi on the 3.0" and an overdriven crank pulley.

 

What other mods did he have? I went from the 3.65" down to the 3.25" with no tune for a while but I'm getting up there in power now.

 

He's got a tms 370 ported Lsa heads tick custom grind cam 1 3/4" longtubes true dual 3" exhaust. Made 7 psi stock crank pulley and 3.625" upper pulley. That 3" pulley makes the biggest difference he's probably at nearly 700hp now. Will find out soon when we have another dyno day