TheSamba.com :: View topic - 40hp big bore with alternative supercharger options

Fri Jul 17, 2009 10:07 am

From personal experience I would not suggest overdriving the smaller vintage blowers. They were originally designed and intended for 1100-1200cc. Yes you can overdrive but they will not hold up long term, will overheat worse and blow apart if you are not very careful in limiting the upper RPM limits. I went through two Shorrocks overdriving them to produce reasonable boost on a 1500cc 40hp. Now I am looking at dual Pepcos or the larger C142B Shorrock which is good up to 2 liters. The only exception might be the Arnott 36hp/40hp kit I have which was quite a bit bigger than the Judson and slightly bigger than the C75BV Shorrock from memory at 850 cfm capacity which was indicated good to 1500cc.

Fri Jul 17, 2009 10:26 am

Quote: The boost pressure refers to 3psi for the larger engines and 6psi for the 1200.

Look like it's consitent with the number people have with a judson and a big bore

So I guess the next question is, 3psi is enought to significantely improve torque and HP?

William

Fri Jul 17, 2009 12:50 pm

xilly wrote: So I guess the next question is, 3psi is enought to significantely improve torque and HP?William

NO, significantely would be in the 6 to 8 range for me.

Fri Jul 17, 2009 1:00 pm

Shorrock wrote: xilly wrote: So I guess the next question is, 3psi is enought to significantely improve torque and HP?William

NO, significantely would be in the 6 to 8 range for me.

...but if we're talking in relative terms any degree of positive boost is going to give an improvement on a stock normally asperated set-up.

Even at 3psi you're forcing more mixture into the chamber to be burnt so in that respect there will be an improvement in performance.

A dyno test however would be the only way to indicate if the gains are worthwhile.

Sat Sep 26, 2009 6:47 pm

I was finally able to check the boost pressure with my big bore and the Judson
I have 3 PSI, as claim on the Judson Brochure