Pulley sizes

[boosted95z]

A forged 355 is being put in my car due to the ring lands being shot, so I am going to bump up the boost a little. I currently am running a 3.12" pulley which is good for 8 psi. Can anyone tell me what the 2.9" and 2.75" will produce compared to the 3.12"?

[Fire67]

Even the 3.12 is fairly small in terms of belt contact IMO. Id start out with a bigger crank pulley to get more belt wrap.

As to your question, no one is gonna be able to tell you what a specific pulley combination will make for boost. What I would do is figure out what pulley combination you need to max the blower out rpm wise, then step down one rpm range with your available pulley combinations. This will help keep the blower in its efficiency range, and make it last longer than if you were to just max it out.

[BLOWNDFIZ]

Justin is right about the crank pulley. About the only option for Vortech now is to have ASP build you a custom crank pulley. I had a 6.75" pulley built and use a 2.75" blower pulley. It's a small blower pulley but I get no slip and my t-trim makes 15psi with this combo. Again boost is relative to intake restriction and I make 15 on a 383 with AFR 210 heads. Smalller displcement and smaller heads would most likely make more boost with the same pulley combo.

IIRC I made less than 6psi with the stock vortech pulley combo on my old S-Trim after I built the 383.

[boosted95z]

Thanks guys, I figured that since I'm only gaining 5 CID and putting in a blower cam, that I won't be losing TERRIBLY must boost. I will probably just take it down a step to the 2.9" and call it at that. If I want anymore power after it, I can add a little n2o or an IC.

[Fire67]

Remember that the boost number isnt what makes the power, its the actual amount of air that the engine/blower combo is moving.

Going 355 with NO other changes is not likely to change your boost level with the same pulleys. Things like a bigger cam, heads, ported intake, etc. will lower your measured boost for the same blower output. But the car will make more power because its moving the air more efficiently.

[boosted95z]

Yeah, I know that much haha. More hp with less boost is always best. I am getting a custom ground cam ordered tomorrow.

[Fire67]

Cool man! What do you have for heads/intake?

[boosted95z]

Cool man! What do you have for heads/intake?

Keeping that stuff stock until I have the money to buy decent heads and intake. If I do anything right now it will be just ported heads and a little porting of the intake. They flow quite well and I don't have to worry about them until I try for 600+ rwhp. Comp only charges $150 for a regrind too.

What I forgot to mention is that the setup uses dish pistons which drop the CR to about 9.2:1. I am only aiming for 550 rwhp and low 11s full weight once said and done.