View Full Version : anthing more then a 10%

07-29-2004, 01:02 AM
ok, i always thought i had a stock pully, then my buddy comes over with a 10% overdrieve pully, and i measure his then mine, and mines smaller then his? how does that hapen? this explains y when belts are just barely old they start to slip.

07-29-2004, 09:22 AM
Did you measure the belt retaining lip or the belt friction surface of the pulley. Is it aluminum or steel. I am asking because I could turn an aluminum pulley for my car in no time on the lathe but a steel pulley is a bit harder to keep balanced. Someone could have custom manufactured the pulley which puts you in a bit of a quandry. IF you have a bigger exhaust and an intake system that can deliver air for that size pulley you might consider keeping it, if not you should consider going to stock to save your HGs. If it were me I would buy a quality pulley because unless it is marked with a manufacturers stamp you dont know which shade tree mechanic built that pulley and you dont know the workmanship behind it you also dont know the quality of material he used building it. I wouldnt risk the SC and the HGs on a pulley that I wasnt positive was PERFECT.

07-29-2004, 10:21 AM
a 10% pulley measures 2.83" on the ribs. You won't find anything smaller than that because the ID on the back of the pulley will end up rubbing the snout without turning the snout down.

Stock 89-93 pullies measure 3.135"
Stock 94-95 pullies measure 3.275"

5% is about 2.935"


07-29-2004, 03:07 PM
You won't find anything smaller than (10%) because the ID on the back of the pulley will end up rubbing the snout without turning the snout down.
But that doesn't mean that you can't spin the supercharger faster than 10%. What about the Overdrive JackShaft pulley. I forget who sells the pulley, but I think it ups the total OD that the supercharger sees, to 23%


BT Motorsports
07-29-2004, 03:52 PM
A 2.70" pulley can be squeezed on without machining the snout, but that puts you at the absolute limit.


07-29-2004, 03:53 PM
A jackshaft pulley won't make the supercharger pulley smaller. That's not what he asked, he is trying to determine what pulley he has on the supercharger.

You need to use a micrometer or at least a set of dial calipers to measure the diameter of the pulley not a measuring tape. And I don't see what the material has to do with turning a pulley Steel or Aluminum will be balanced if they are turned on a lathe.


07-30-2004, 01:02 AM
well exhaust is open, but this has 2 pully puller holes already driled so it must be custom, i guess in theroy how fast can i actualy spin my m90, its geting a port job very soon and i want to know how fast i can spin it, i will make my own pully one i get some safe specs to work with.

07-30-2004, 07:57 AM
Putting the smalest pulley on there isn't always going to net you a gain, sometimes it can cause a loss in power. What boost level are you at right now? Sounds like it is a custom pulley. If it is bare aluminum you might want to have it hard anodized so as not to wear it out. Also the smaller the pulley you put on there the less wrap you have on the belt and the more likely you are to slip. Adding larger tensioner helps.