20% od belt size

well i tried the search feature but i guess it is temporarily down. on that note, i am looking for the size/width of a supercharger to jackshaft belt for my car. i have both the 10% jackshaft and 10% s/c pulleys, can i order it from charles or perhaps somewhere else cheaper? any info helpful, thank you

anyone? bump

Depends what pulley's you are using because some 10% JS pulleys are different sizes. You should be able to use a stock belts (make sure they are new). Is the stock belt too short or too long?

like a quarter inch to a half inch too long. i need the 10 rib belt or the 12 rib belt that you just cut the 2 ribs off of. the belt actually cut 2 ribs off of itself b/c of a loose fit, and yes i do have a new tensioner.

What pulleys are you using? I can't make a belt recommendation without knowing what pulleys you have. What belt do you have now that is too long? I have belts in stock but I need to know what one you need.

i have the magnum powers 20% OD kit, which includes the 10% od aluminum jackshaft pulley and 10% steel supercharger pulley. the original belt i had used came with the 15% OD kit from magnum powers. i recently upgraded to the 10% superhcarger pulley because my old supercharger bored out the keyway on my original 5% pulley. both pulleys are from magnum powers.

Sounds like you need the 39" belt. They are kind of expensive - around $40. No one is likely to stock one, so you'll have to order it. How much are they from MP?

The other option is to use the 40" belt and raise the supercharger up but they aren't much cheaper although I do have them in stock. There aren't any belts in between those sizes so you'll have to make one or the other work.

Have you seen this thread? It discusses various belt lengths that people have used. It also has info on how belts are sized so you can figure out which one you need.

http://www.sccoa.com/forums/showthread.php?t=92077&highlight=belt+length

I guess I will ask Charles if I cannot find the correct belt online. thanks for the help from both of you!

also for anyone also looking for these belts, i found on the link mike provided, another link to the list of belt sizes that good year carries. 4120390 is the part number for a 12 rib 39 inch belt. the 39 only comes in 12 ribs but if you have a steady hand you can shave off the last 2 ribs. thanks again guys

Gates also makes that belt in that size Gates K120390. But do not cut the ribs you might have to end up returning it Ask me how I know.

It will be too much of a tight fit with the 20% MP OD kit. If you have a stock tensioner pulley you might have better luck. You must be able to move the tensinoner freely by removing the tabs on the back part. The only belt that you can turn into a 10 rib belt is a 39" and the 40" After you try it out you will see that only the 40" will work but it will be too loose and even if you clock the tensioner it will not work. The only thing that will work is removing the SC and shiming it up with washer under the mounting points, and/or removing the AC compressor accesory bracket and enlarging the mounting holes in a way that you can move it all to the left/down away from the SC to give it enought tension.

I have the Super Duty tensioner pulley so with it the 39" belt does not work. Good luck with yours, you will likely have to return it and go back to the 40" belt and do as I said.

that's strange, how come shaving the ribs off does not work with the 39 inch belt? with the original mpx kit charles gives you a 12 rib i guess 40 inch belt, and you pretty much only have the option of cutting off the last 2 ribs?

johnrada said:

that's strange, how come shaving the ribs off does not work with the 39 inch belt? with the original mpx kit charles gives you a 12 rib i guess 40 inch belt, and you pretty much only have the option of cutting off the last 2 ribs?

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Because it's too short. I wasn't aware that it was too short for the 20% pulley set.

I just did not want you to waste your money by cutting it up and not being able to return it. Thats all.

It will depend on the tensioner pulley, if its smaller then stock you might have a chance. Just try it on before cutting it up so you are able to return it if it does not work.

ok. besides that you would recommend the 40 inch belt on the 20% pulley set?

That would be your only other option. But you must do what I mentioned above.

I think the MP spring is stretching my belt. I noticed my Gates K120400 belt was touching itself under the SC pulley where the tensioner pulley makes contact. It has about 3,000 miles on it. So, I put on a new K120400 belt and saw a nice 1" gap. I reclocked the tensioner to ensure travel to maintain tension. After an 80 mile trip I noticed the 1" gap had been reduced to about 3/16" . The tensioner had not moved from its mounted position on the accessory bracket either. All I can attribute this to is belt stretch. I ran the engine for a minute after initial install to make sure alignment was correct before the trip. I might look for a smaller diameter tensioner pulley (currently running AC Delco/Napa #38023) to help alleviate this issue. The belt edge running from the JS to the SC covers a long run and is probably allowing it to touch the top belt edge when under high RPMs.