Anyone Know the SC pulley contact degree on 08 gt500

[FordTech24]

I can not find anywhere the Supercharger pulley contact degree on a 2008 gt500.
I am changing a pulley for smaller size and dont want to add a idler So trying to find the Degree so I can put it in a formula.
Stock belt is a 84 7/8 so I am guessing the degree is about 300, So going to try a 83 7/8.

 

[gtbite98]

When going to a smaller pulley with the stock belt, means taking up slack with idler. You can try a smaller belt but it might slip!

 

[08KR525]

Not trying to tell you what to do, but VMP has the idler for like $70. A replacement belt is $50. That's not even telling if you can find a shorter belt for one. Take it from someone who just had to change the belt because I shredded it. It ain't worth it if all you have to do is replace an idler that no one can see anyway. Changing that belt is a PIA.

 

[IronTerp]

I can not find anywhere the Supercharger pulley contact degree on a 2008 gt500.
I am changing a pulley for smaller size and dont want to add a idler So trying to find the Degree so I can put it in a formula.
Stock belt is a 84 7/8 so I am guessing the degree is about 300, So going to try a 83 7/8.

I have never heard of someone figuring out/knowing the "contact degree" for the various sizes of super charger pulleys. Pretty neat concept. Below is the list of applicable 10 rib belts from Gates for the GT500's. If you're adding a 2.50" upper, I'd probably consider the 83.05" belt. You can get them from RockAuto for $26 plus shipping.


Gates Micro-V 10 Rib Supercharger Belts - GT500
K100810.....81.61"
K100822.....82.20"
K100830.....83.05"
K100840.....84.62" (our factory replacement belt)
K100852.....85.33"
K100860.....86.08"
K100870.....87.03"
K100877.....87.76"
K100879.....87.93"
K100891.....89.13"
K100895.....89.42"

 

[wingsnut]

Not sure what contact degree really is, but will this help at all?
Per the Machiners's Handbook, 20th edition:
Light duty V-belt Sheeve dimentions
2L
Effective Outside Diameter in inchs
Under 1.5-- 32 deg. width at full dia .240
1.5-1.99-- 34 deg. """"""""""""""""" .243
2.0-2.5-- 36 deg. """"""""""""""""" .246
over 2.5-- 38 deg. """"""""""""""""" .250
depth o f groove .250

3L
Effective Outside Diameter in inchs
Under 2.2-- 32deg. width at full dia .360
2.2-3.19-- 34 deg. """"""""""""""""" .364
3.2-4.2-- 36 deg. """"""""""""""""" .368
over 4.2--38 deg. """"""""""""""""" .372
depth of groove .406

4L
Effective Outside Diameter in inchs
Under 2.65-- 30 deg. width at full dia .485
2.65-3.24-- 32 deg. """"""""""""""""" .490
3.25-5.65-- 34 deg. """"""""""""""""" .494
over 5.65-- 38 deg. """"""""""""""""" .503
depth of groove .490

5L
Effective Outside Diameter in inchs
Under 3.95-- 30 deg. width at full dia .624
3.95-4.94-- 32 deg. """"""""""""""""" .630
4.95-7.35-- 34 deg. """"""""""""""""" .637
Over 7.35-- 38 deg. """"""""""""""""" .650
Depth of groove .580

Chip

 

[FordTech24]

Thanks for all the info, I was going to try the 83" belt would come close but not close enough, Decided to go with a 90mm pulley to make up for the slack, but got new pulley that they use on ford diesel 6.0l that look stock and its a 90mm outter, with 17mm inner, and used for a 10 rib belt. Worked great and It looks Stock so no one can notice the difference. The part number I used is a gates 36234. I was amazed with 145hp gain from smaller pulley, intake, and tuned bob kurgan from stock numbers. STOCK WAS 400HP 413TQ at 90F temp, After 545 and 565TQ at 70F temp. I know temperature probably had some to do with it but numbers came out way better then I expected. Very pleased working with bob and how smooth the tune came out. And now I know what they mean it really wakes the Shelby up with at tune, pulley, and intake.