10% or 5%

Mark B. White

Registered User
my friend just wrecked his 93 sc, and it has a way smaller sc pulley on it then my 94 so how can I tell if it is 10% or a 5%??? What are the outer diameters of the two????
 
the outer diameter for the 10% is 3.1 inches, if im not mistaken...i dont know the 5%, sorry.

stephen
 
Most likely if both cars are stock, then thats the difference in the years of blowers. The '89-93 SC/XR7's came with a pulley that was smaller than what came on the '94-'95's. If you where to buy that pulley and put in on your car, yes it will fit, you would pick up a few extra pounds of boost.
 
Mark - if you swap the stock '93 pulley onto your '94 it's equivalent to a 5% and, with the Flowmaster system that would be safe enough.
Jim.
 
Mark B. White said:
my friend just wrecked his 93 sc, and it has a way smaller sc pulley on it then my 94 so how can I tell if it is 10% or a 5%??? What are the outer diameters of the two????

Plagiarism is the sincerest form of flattery. :D

Originally posted by Andy 94Sc
Supercharger pulley diameters

This question comes up a bit on how to identify a pulley, probably will more and more as modified cars end up on the used circuit. These diameters I measured "peak to peak" on the metal ribs where the belt rides.

Stock '89 - '93 => 3 1/8"
Stock '94 - '95 => 3 1/4"
March 10% ====> 2 7/8"

Magnusen reports and John Shelton agreed with the following.

Magnusen standard "S-Port" => 3.135" (3 1/8" same as stock '89)
Ford SVO (5%) ~ 3" (Magnusen says 2.935" John measured 3")

There are more pulleys out there, I am not sure of those diameters anyone have them? I am specifically thinking of the S&S enterprises pulley that was advertised a lot in the early '90's with the "Soaring Spirit" T-bird book. I think Superchips supplies a pulley with thier chip, not sure of that diameter either. ASP?
 
We should put this information in the FAQ forum under "SC Pulley Sizes" or something. These answers could likely be found by doing a simple search also.
 
I think you need to be careful with the sizes. Because most of the aftermarket (March, Ford SVO, ASP etc ) were rated against the '89-93 Superchargers. So stock '89 was 3.1/8" dia; 5% overdrive was 3.00" and 10% was 2.7/8" (which is what my alum ASP is on my '93 5 speed). If you use those pulleys (particularly the 10%) on the '94/95 you will be overdriven. I tried the ASP on my '94 and it would light-up the tires and go off the boost gauge (over 15psi), when the auto downshifted from o/d. So I promptly took if off (as I didn't want to blow my HG's) and used the stock '93 pulley on my '94; giving me about 5% and 12-13 psi of boost on a mildly modified motor (Flowmaster Force 2, S&B cone filter, 75mm Bullit MAF, 70mm BBK TB, 3/4" raised top, IC fan, etc).
Jim.
 
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