Supercharger Pulley - smaller for more boost

[VF Sleeper]

So I've had the Harrop 2300 on my Calais S1 for just over a month now. The current SC pulley is 85mm and it's running 6-8 psi boost.

A new smaller pulley (80mm) is a couple of hundred bucks and plus a re-tune. This smaller pulley should give it 8-10 psi boost.

I'm thinking why the hell not? More boost must be better and 8-10 psi isn't that much. I'm most interested in more power and torque in the 1000rpm to 2000rpm range where it's a bit soft.

Have anyone else done a smaller SC pulley? The other option is a 75mm for 10-12 psi? I've got a stock bottom end.

 

[07GTS]

ive got the 80mm and the 75mm, but i also have the toothed rear drive that also adds to the ratio, the 80mm front i was on 13-14psi, the 75mm was about 16psi, also make sure your belt is right length as going smaller pulley may put the tensioner out of range, they will handle around the 10-12psi easy

 

[VF Sleeper]

07GTS, I didn't know you could change the rear pulley. I can't even see a rear pulley on mine. Have you got a Harrop?

What sort of interest increase in power did you get with each step down in pulley? Any downside?

 

[07GTS]

u prob have the newer one, mine is the HTV2300, not sure i went from n/a boltons to the blower and camshaft gained 160rkw, then ethanol and better cooling and gain alot more, u will have to keep an eye on it as camshaft will decide alot to what the boost will do, i never got onto a dyno and now im doing full build so will be very different, it usually just adds to what u have already if timing will cope with the increase but u will get gains think its roughly 30hp per psi boost or something around that if all other conditions stay the same

 

[crew chief]

I ran the 2300fdfi like yours 75mm 11-12psi with a 6PK2385 belt with no issues for a while but have changed to a 70mm and 6PK2370 giving around 14psi

 

[daves8]

Did you change lifters and cam too?

I have a S1 Calais and have considered a 2300 but everyone said I need to remove all DOD gear and new lifters

 

[crew chief]

Did you change lifters and cam too?

I have a S1 Calais and have considered a 2300 but everyone said I need to remove all DOD gear and new lifters

Yeah I sure did, way before going the blower.

 

[VYCommodore76]

smaller you go with the snout pulley, the more likely you are to get belt slip.

 

[07GTS]

the standard 6pk gates belt i could strech in an after noon of driving, the gates blue racing belt 6pk lasted longer but i snapped one during a wot gear change, i now have the 8pk setup and use optibelt truck power series belt much better

 

[VF Sleeper]

Did you change lifters and cam too?

I have a S1 Calais and have considered a 2300 but everyone said I need to remove all DOD gear and new lifters

Yes, I did heads, cam, lifters, roller rockers, pushrod, dual valve springs & DOD delete