MP 10 rib JS and SC pulley system+tensioner pulley=problems

ricardoa1

Registered User
Is anyone having problems with the belt overhanging from the tensioner pulley?

I bought the Truck Super Duty pulley that is wider and and at least two of the ribs on the belt hang off it on the back side closer to the engine.

How do I fix this? Anyone having problems with this the rest of the tensioners sport the Motorcraft steel pulleys I dont want to go back to the plastic ones.
 
I am using 90mm Cobra tensioner pulleys. In order to use them you need to mod the tensioner.

tension5.JPG
 
I am using 90mm Cobra tensioner pulleys. In order to use them you need to mod the tensioner.

tension5.JPG


How close is the lower 90mm pulley to the crank pulley? It looks like real close. I was planning on actually extending the arm on the tensioner but it looks so close. It is definitely a to do mod for me

Ken
 
Looks like an expensive fix. Looking for a cheaper alternative.. Those look great by the way.

I was using some extra wide pulleys made by Heartland especially for the 10 rib setup and the belt overhung about 1.5 ribs toward the motor with them too. Never caused any problems, it just looked wrong.

David
 
So I can run this like this? Ill post some pictures of it. Problem is that if pulley was wider on the inside it will start to rub on the tensioner arm.
 
How close is the lower 90mm pulley to the crank pulley? It looks like real close. I was planning on actually extending the arm on the tensioner but it looks so close. It is definitely a to do mod for me

Ken

The lower 90mm tensioner pulley is 3/8" from the Magnum Powers OD crank pulley.
I still need to talk you into extending a couple tensioner arms for me.

:)
 
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I'm going to keep an eye on this thread, but I'm running the 10 rib with the stock idlers with the MP springs....they hang over but they are tight..I haven't had any problems but my car is a track queen it doesn't have to DD at all
 
The lower 90mm tensioner pulley is 3/8" from the Magnum Powers OD crank pulley.
I still need to talk you into extending a couple tensioner arms for me.

:)

I ordered a pair or 90MM pulleys yesterday so I am going to modify a set of tensioner arms and see how they look. I will keep you in the loupe as to how they look. I dont think they will be to hard to Mod

Ken
 
I guess I don't see the point to doing this. If your F250 SD tensioner pulleys are running off the belt it seems to me that you have other issues like a worn tensioner or something. Are the Cobra pulleys actually wider?
 
I guess I don't see the point to doing this. If your F250 SD tensioner pulleys are running off the belt it seems to me that you have other issues like a worn tensioner or something. Are the Cobra pulleys actually wider?

It is mostly for looks.
The F250 tensioner is about 1.25" wide, where as the Cobra pulley is 1.5" wide. It seems to me in order to prevent the supercharger belt from over hanging the pulley in the back, you would need to slightly mill down the tensioner mount spot on jackshaft.
 
It is mostly for looks.
The F250 tensioner is about 1.25" wide, where as the Cobra pulley is 1.5" wide. It seems to me in order to prevent the supercharger belt from over hanging the pulley in the back, you would need to slightly mill down the tensioner mount spot on jackshaft.

I would say for me that is mostly looks and I will be doing away with the soft alum pulleys I have that generate dust. I am not looking for a better way to prevent slip if anything I am wondering if I need the bigger tensioner springs on a whipple. The original whipple pulley is only a 6 rib anyway.

Ken
 
I would say for me that is mostly looks and I will be doing away with the soft alum pulleys I have that generate dust. I am not looking for a better way to prevent slip if anything I am wondering if I need the bigger tensioner springs on a whipple. The original whipple pulley is only a 6 rib anyway.

Ken

For the speed you likely turn your twin screw, you would be unlikely to see belt slip with a 6 rib. Generally the twin screws when within their RPM range don't take as much effort to turn as the roots style.
 
I have a A/C tensioner pully and arm setup from a staight 6 mercaides semi diesel. The center mount bolt is the next metric size up so I'll have to drill and tap for the bigger one. diameter of the pulley seems about the same just about 1/2 inch wider!! Happens that the truck had the A/C recently removed and never put back on. Due to the transmission being toasted theres not much incentive to work on it. Getting a 96 v6 tbird, putting the sc engine n random parts in that one. Also wife ran over a curb, ripped and tore the rear bumber in several places:(, just one blow after another
 
For the speed you likely turn your twin screw, you would be unlikely to see belt slip with a 6 rib. Generally the twin screws when within their RPM range don't take as much effort to turn as the roots style.


I will be running a 1 to 1 jackshaft pulley and a 3.75 SC pulley so I will be turning the blower considerably slower than a stock M90

Ken
 
I have the Diesel pulley and no overhang issues thanks to zimmer for hooking me up at the Dayton meet.
 
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