I'm putting the M7 16% pulley on my '03 MCS and need to know
if there is a consensus regarding the proper belt to use with a
stock crank pulley.

I have searched and found a lot of conflicting info. Some say
use the stock belt, some say use the JCW belt, and I have
found references to three different NAPA belts (25-060547,
25-060535, 25-060539). So which is best/correct?

 

I have this pulley on my silver car, and I put on a NEW stock belt when I did the install. I have had no problems at all.

 

We've found that the stock belt works fine with the 16% or the 16% + 2% crank. You can use a slightly shorter belt, such as the JCW, with no problems as well. In short, it's a user's choice issue.

 

Will
Nice to meet you I'm the M7 distributor in Hawaii and I'm also using the JCW belt with the 16/2 M7 pulleys.

 

Thanks for the input, guys.

 

I put the 16% on at 5k, and kept the stock belt on. I now have 16,xxx miles w/ no problems at all.

 

Pete,

I've used the NAPA 0535 with no problems. I did have a problem with the JCW belt slitting. Went back to NAPA, no problemo.