hey im thinking about going from stage 2 to a 2.9 or 2.8 pulley can someone tell me everything i have to do for it to work right and how much horse power would that give me?

 

You can get a polished 2.9" pulley from Nate (nherbst). His website is www.smoothflowpulleys.com. I have his 2.9" and it works good with the gm stage 2. I would not go under a 2.9" because your IDC could get high. People run 2.8"s on it but I would stick with 2.9" FYI gm stage 2 pulley is 3.06" and gm stage 3 is 2.99". Each .1" you drop is approx. 1 psi.

 

Just loosen the bolts on the pulley, loosen the belt by pushing on the belt tensioner, switch the pulleys, slip the belt on and you are set, its like a 5 min job, not a hug difference in peak HP from a 2.9 - 2.8, but alot more TQ with the 2.8, just be careful I would stick with the 2.9" to be safe. (I would quess may 4-7hp & 10-15ft/lbs difference between the 2.8-2.9)

 

k thanks guys. but since i do have the 3.06 pulley would i need bigger injectors for the 2.8? or need to tune it? and whats the hp increase from 3.06 to 2.8? sorry for all the questions im still kinda new with it

 

NO just get it tuned but this has been a argument on here for years though

 

don't forget the tune you'll need for the new stuff, HPTuners seems to be the tool of choice. Might want to think about cooling mods too and 1 step colder plugs.

 

There is a huge debate on this site about running a 2.8" pulley with the stage 2 tune. Some people will say yes its fine, others will say no its to much and you ill be maxing out your injectors. I have been running a 2.8" pulley on my car for over a year with absolutaly zero issues at all. The safe bet however would be to just run a 2.9" pulley. The debate is on the injector duty cycle, most will say that running a 2.8 will cuase your injector duty cycle (IDC) to be well over 100%. A 2.9" will be just under 100% IDC. The concern is that your injectors can go static and stay open when over 100% possibley causeing e4ngine problems. Also when you run the 2.8" pulley you dont get the full benfits becuase you really should have some additional cooling mods becuase you are increasing the intake air temps when you compress the air or add boost. You could meet in the middle and get a 2.85" pulley. But it wont be much faster with the 2.8 pulley over the 2.9. Its mostly more tourge in the rpm range and faster to hit max boost with the 2.8.

If I knew what I know now back when I installed the 2.8, i probaly would have just put the 2.9 on

 

k ill probally put the 2.9 on then, and what did light'bolt mean by using one step colder plugs

 

When you drop pulley sizes you need so shrink the gap on your spark plugs, means the same as going to a colder plug. So you should pick up a set of new plugs (copper), I think the ZEX plugs are the best becuase they are already pregapped(They are more expensive) but also the NGK BKR7E's gapped at 0.040 are perfect for that pulley size. Most auto stores carry the NGK's and then you can gap them @ 0.040....stock plugs are gapped @ 0.045

 

k cool ill do that thanks a lot