How much boost should i be making with a 6'' crank pulley and a 3.33'' sc pulley? how much if i change to a 2.95'' sc pulley?

 

The stock Vortech system (6" crank pulley, 3.33" blower pulley) for a stock LT1 makes 6# boost at around 6K rpm. I wouldn't run higher boost than that unless you run forged pistons and an intercooler or alky injection. If you do decide to pulley up, first add a 7" crank pulley to minimize belt slippage. The 7"/3.33" combo should get you 9# of boost.

 

Do you measure outside diameter or from the grooves.

 

measure by the grooves...

Yeah mine hit almost 6psi on my 6" and 3.33", it was a little lower due to my cam and heads. Not to hijack this, but does anyone know what a 6" crank and a 3.0" blower pulley will do? 8ish psi maybe???

 

i talked to vortech and they said to figure about 2#'s per pulley size. I have the same set up and mine makes 6-7 lbs and I bought the 2.95 pulley, 2 sizes smaller and they told me to expect 11-12 lbs.

 

Again, if you do decide to pulley up, first add a 7" crank pulley to minimize belt slippage. The 7"/3.33" combo should get you 9# of boost.

 

hey obe1, what size belt do you need when you go to the 7" CP? and does anyone make them besides vortech.

i dont need a new belt yet (im still running stock pulleys), but i know vortech wants way too much for theirs.

 

I'll look up the size tonight when I get home from work; Vortech doesn't make the belt, you can get them from a local parts store. I'll let you know the brand; it was either a Gates or Goodyear belt.

 

cool. i figured that a local autostore would carry the same belts. a replacement belt for the standard 6psi kit, vortech charges 42 bucks.

 

OBE1 - If you're talking about the belts you and I are currently running for 9 psi, it's a Goodyear Gatorback/Parts Plus 4080425/8PK1080 42.5"/8 rib

 

Thanks Brian!