I have an alta supercharger pulley installed but it doesn’t say what percent it is. It is of the older version. I looked online and the same design, colored pulley I have come in both 15 and 17. I’ll upload a pic of how the pulley I have installed looks like. I don’t want to have to remove the pulley to figure it out. How can I figure it out?? Thanks!

 

Perhaps you can try to measure the pulley size in mm with a flat ruler . I think the stock s pulley was 65 mm , so a 15 % would probably be around the 57 mm mark and so on .

Also If the previous owner used the proper belt size , the belt number may be a good indicator also.

Not 100 percent on these numbers , but just an idea .....

 

Use measuring calipers (you can borrow a set from some of the auto parts stores, )
and measure from 'tooth to tooth' or peak to peak of the groove teeth. 65mm = stock S 58mm = 11% JCW 55.25 = 15% etc. Ignore the flange diameter.

Some ancient discourse on the subject:
https://www.mini2.com/threads/jcw-tu...y-size.167370/

 

^^^ Good suggestion, however requires removing the belt for sufficient measurement clearance as shown with my oddball 8-bolt pulley. I measured prox 60mm outer flange diameter which I think equates to 15% reduction...

 

Thanks for that link to the ancient discourse!
I really enjoy reading the contemporaneous discussions with these cars, and also as a byproduct often get prompted to go rabbit holes --- that thread was no exception and I wound up on a blog ( love blogs too as they tend to be quite comprehensive, and thankfully many of the older ones are still up, but sadly their peak of popularity is past, it required a good bit of work to maintain a good blog!) oh on a ramble ironically the blog I found was Robert's Random Ramblings!

http://robert-apon.blogspot.com/

He is an American who imported and fitted up a JCM 225 kit, so it's really cool to see, gotta go back to the archives of 2007.

Some pics from his blog-

the red JCM pulley:



JCM headers:



JCM flywheel:



:

Someone asked him hey! where can I get these parts?



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Apologies for the slightly off topic diversion!

 

What belt-size are you running?

 

The flywheel photo looks like it was taken by M.C. Escher. I can't see the perspective the right way.