smaller pulley

[pavement pounde]

I have with my 454 setup the stock 3 3/4 inch pulley bud I recently purchased a 3 inch pulley.
Would the 3 inch be to small and hurt my SN93 ?
At the moment I see 7 psi with modefied impeller above the trottle body.
Thanks

[speedytang]

What size is the crank pulley?
What RPM do you shift at or does the 454 stop pulling.
The last 454ss I was in back in '92 stopped pulling at about 4800 rpm.
Just remember the Max RPM for the SN93 is 38k RPM before you risk the Balls and Impeller shaft

[pavement pounde]

I don't know the stock crank size.
The cam and springs are stock to and it shifts in drive at 4500 rpm.
I believe there is no point in manual shifting.

[speedytang]

I would guess the 6" Crank pulley and that would put you at 39.5k rpm at the Supercharger. It puts you close just don't go over 5k rpm for extended times and you should be at a safe margin

[pavement pounde]

Thanks !
Tommorow I check the crank pulley to be sure.
Could you also say howmuch extra boost the smaller pulley would give ?

[speedytang]

Your problem is going to be belt slip. If you can keep the belt from slipping you could see 2psi additional but that would also mean a fuel increase of 18%.

[pavement pounde]

I took measurements today and the crank pulley is 7 inch.
That shanges things, I gues.

[speedytang]

That will be another 8k rpm at 4800 rpm.

[pavement pounde]

That will be another 8k rpm at 4800 rpm.

8K slower, if the crank is bigger then the blower goes slower right ?
How do you calculate the speed of the impeller anyway ?
It has been awhile for me that I learned that at school ;)

[speedytang]

8,000 rpm faster. You will be at around 49k rpm at 4800 engine RPM.