Jackshaft pulley

black95sc

Registered User
Hi all,

I have Auto Specialties Performance Underdrive Pulley Systems and 10% Blower Overdrive pulley on my 1995 SC.

What is a Jackshaft pulley? Should I get it?? Will it help??

Thanks in advance!

Thomas
 
Thomas,

Good question. There is already a jackshaft installed on your car from the factory, but you can buy a fully machined aluminum version from Super Coupe Innovations that is lighter in weight, and therefore frees up crank HP. If you want a good modifcation that is easy to install, and has good cost vs performance gains, I would recommend you look into buying one.

There is a group purchase taking place on these within the GP forum. I think you can buy them for $140 now, or somewhere in that price range.

Good luck.
 
Bill,

Thanks! One more question, so are my ASP underdrive pullies different from the jackshalf pulley?

Thanks,
Thomas
 
Underdrive vs. Jackshaft

The underdrives have NO effect on the speed of the jackshaft or the supercharger. They only affect the (1) alternator, (2) water pump, & (3) the NON-jackshaft pulley on the crank.

The crank pulley had 2 belts on it. One for the Jackshaft & one for the serpentine belt. The jackshaft pulley is OEM size. It's the serpentine pulley that is a different size.

I have underdrives & 10% on my car. No problems at all.

68COUGAR
 
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Thanks 68COUGAR!

How much performance gains should I expect from the jackshaft pulley?

For those that have the jackshaft pulley installed, are you happy with it and where did you get it from?

Thanks,
Thomas
 
The other alternative that you can go for is a 10% aluminum jackshaft pulley with a stock sized SC pulley..This way you get more belt contact on the pulley which equals less belt slippage and the advantage of a lightweight jackshaft..ESM sells them along with a 10 rib belt upgrade..21psi of NO belt slippage here:O)
 
DamonSlowpokeBaumann said:
The other alternative that you can go for is a 10% aluminum jackshaft pulley with a stock sized SC pulley..This way you get more belt contact on the pulley which equals less belt slippage and the advantage of a lightweight jackshaft..ESM sells them along with a 10 rib belt upgrade..21psi of NO belt slippage here:O)

21psi? Is that right? Would the stock bottom end hold up to 21psi? What does ESM stand for?

Thanks!
Shane
 
Embree Specialty Machine. = ESM .

Their parts are available through Blue Tounge Motorsports:
http://www.bluetonguemotorsports.com/ESMParts/Parts.html

21psi is not a concern for the bottom end. The SC block has a very strong bottom end. It's the head gaskets you need to watch out for.

I haven't see weights for the ESM part listed. It's the light weight that gains the HP. Since the ESM part is a larger pulley than stock it may not have as large of a weight gain as the stock diameter aluminum piece.

If you don't want to go to a 10% increase in blower RPM's, then look at the stock sized part. But if you were considering a 10% or greater (10% jackshaft + 5% SC pulley) increase then start with the 10% jackshaft unit.
 
Damon has failed to point out that he also has a fully ported blower and the fact that the M90 blower is not efficient above 16psi. :p

The ESM aluminum pulley is not significantly lighter than the stock pulley. It does spin the blower faster by about 10% but that is not a good idea unless you have already replaced your headgaskets.

You will be better off with the ASP/SCI pulley package.
 
IASNT SUGGESTING HE GO WITH THAT BOOST NOR COULD HE WITH A STOCK BLOWER,,,However I get zero belt slippage and many people I know with 10% pulleys get belt slippage due to the smaller pulley (less belt to pulley )...That is what I was conveying information wise:O)
 
How do you know you have 20 lb of boost.My gauge hits a stop
just past 15 lb of boost.

What type gauge do you all have.And were do you mount this 20lb plus gauge.

RANDY
 
The pillar is where my 30 psi gauge is...

FRPPWheel2.jpg
 
I have trouble believing the 21 psi boost part. I'm not saying someone is lying about it, but I've seen 18 psi on my Autometer before with over 20% overdriuve, and I can't imagine anyone seeing much more than that. Just like my stock boost gauge is off by about 2 psi, I would imagine that is possible with any gauge, and the reading may be innaccurate.

IMHO. :p
 
I was pinning the stock gague but figured it just wasnt accurate. I went to the track and my car would just die top end(perhaps pull out timing) . Felt real good downlow however..SO I figured maybe Im getting a tad more boost then I should be..I hooked up an autometer gague and low and behold 21 psi consistently. As far as modifications to my car at the time I had every bold on imaginable. From Kooks headers to magnum powers intake to a spearco IC to ESM ported blower with 10/8 rib upgrade ect ect ect..Granted with a larger cam my boost would drop (by how much dependant on cam), however the fact is I did indeed get 21psi with what seemed to be 0 belt slippage. Belive it..Or not....

This is my Dave Dalke disclaimer (inneficient or not)
 
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