Belt Size

[BeckSVT]

I recently just purchased a Gen 4 2.9 Whipple and was trying to figure out what size belt I need? I have the 3.5 upper with Metco 4 piece idler kit 3 100mm idlers and 1 90mm. I have the stock lower with the stock alternator pulley as well.
Please let me know and if you have part numbers put them in your comment.
Thanks in advanced.

 

[TerminatoRS]

There's a belt length chart posted on here somewhere. I think your setup uses fairly common pulley sizes so I'd bet what you need will be listed on that chart. But if I had to guess, I'd say something like a 77-77.5".

 

[olympic]

03-04 Cobra Supercharger Belt Chart - LMR.com

According to the chart you add 1" for the snub idler and 1/2" for each 100mm idler. So add 2.5" for a total of 78".

FWIW I ran a Gates RPM K080797 79.7" belt with a 3.5" upper but I also have a Metco lower (stock diameter) and a Mechman alternator so I'm not sure if those things affect belt length. The 79.7" belt was a little on the loose side though. When I swapped to a 3.25" upper I was able to squeeze on a 78" belt.

I'd say start with a 78" belt.