ive got a 07 sierra with the 4.8 and whipple 2.3. Right now it has the 3.625" pulley on it making 9psi. I'm trying to get up to 11-12 psi. What size pulley will I need? I ordered the 3.325 and 3.375 just wondering which one I should start with. It made 462 with current setup and I'm trying to hit 500. Do you think 3psi will get me that last 40hp??

Other mods are: American Racing long tubes (catted) into magnaflow cat back, cam (DUR @ .050" 216*/ 224*LIFT .551/.551 LSA 115*). Level 6 finishline 4l65E, 2800 stall, 4.10's.

 

nobody?

 

You should have any issue gaining 40hp with 3psi. As for the boost increase, why not ask whipple when ordering the pullies?

 

i called them first and they recommended the 3.325 and i told the guy thats doing my tuning and he said he feels like thats too big of a drop. It sucks cause ive been doing all kinds of stuff to my truck thru email with the shop cause im in Afghanistan at the moment.

 

on a tvs 2300 they say 3lbs of boost will net you about 60hp .....20hp per pound of boost.....good luck with your goal

 

I would start with the larger one. It's only a half inch bigger... not sure why you bought 2 that are so close in size though.

I also couldnt tell you what the increase in boost will be, but I can almost guarantee that you will see the power you want from the larger pulley. The loose rule of thumb for a maggie is that every tenth of an inch you drop in pulley size will net you about 1 PSI. By that math you will get about 3# from the swap.

 

well i called whipple first and they said use the 3.25 (3.325 was a typo) so i went ahead and ordered that. When i told the guy doing my tuning he said he thinks that was too much of a drop and would put me over 11-12#'s so i ordered the bigger one too (3.375) just in case. I dont want to have to pay for multiple dyno sessions because i had to wait on pulleys.

 

thanks for the input though guys!!

 

also with that being said... i will have a few whipple pulleys for sale in the near future haha

 

2.3 Whipple, OD balancer, 3.25 pulley on a 6.0 = 10 pounds.

I have headers (2"), cam, 102MM TB, yadda, yadda. Cant see why a 3.25 on a 4.8 wouldn't get you at least 10 lbs.