dws6

On stock motor w/ cam in sig. what will the boost be with a 5" pulley and also with the 4" pulley?
Are there any sizes in between them?

kman0066

I don't know the boost levels for a 4" or 5", but the one sitting in my garage is about 4.6"-4.7" and I've been told I'll make about 9 PSI with a cam that is similar to yours, that's going to 6500rpm.

They make all sorts of sizes in pulleys, contact Procharger or an authorized dealer, they can probably get you the exact boost level you want.

Urban Legend

iTrader: (5)

There is a 4.5. I have never heard of a 5 inch pulley.

KrazyWS6

Im running a 4.5" making 7psi with full exhaust and a stall. But a bone stock car with a 4.5" pulley makes 8psi. With a 4" you should make 8psi-9psi.

Urban Legend

iTrader: (5)

Call Bob at EPP. If he does not have your answers its because the answers are non existent.

EPP

iTrader: (22)

Man, you're giving me a big head... lol Thanks, I'll try to live up to it. ATI's largest 8 rib pulley for the F Body LS1 engines is a 4.5" pulley, although we found one that was sent to us with a 4.7" pulley on it. I would suspect you will see approx 7 to 7.5 pounds of boost with this pulley with the cam you have. Stock engines/stock exhaust see about 9 to 10 pounds with this 4.5" pulley. With a stock botttom end I would suggest staying with this pulley, as your power level will be up at what I consider to be the limit to the stock bottom end.
Guessing on the boost that will be made, and it is only an educated guess, is fairly hard to do, as there are a lot of factors that can throw off what the engine should see. Worn valve springs, belt slippage, too much leakage through the bypass valve, etc. The blower belt stretches after a little use, and I recommend retightening the belt after the first half an hour of use, and the belt has to be tighter than you think it should be. Bob

dws6

Well the pulleys I have are 4" and 5" measured with measuring tape. And these numbers are printed right on the pulleys. 4.00 and 5.00
Where would the boost be with the 5.00 inch, 6lbs?

Will the boost be to high with 4 inch w/ the cam and exhaust in my sig and stock internals?

I am shooting for 550 rwhp with the lowest boost possible.

Where do you guys think I will be with either of these? Best guess.

Thanks,

andereck

A .100" change in pulley diameter is close to 1 psi on a small block. Also for every .250" change in pulley diameter belt length will change about .400" with most brackets....as a rule of thumb.

Drewstein

I think 6 to 7lbs is what your 5" will do. Maybe a 4.75" for 8lbs would be perfect.

I think it's possible to pick up pullies in 1/4 sizes, so you can go with a 4.75" to get the boost just right.

As far as stock internals go, it's all in the tune. 550rwhp is pretty safe for an LS1.