I recently bought an 03 MCS with 57,XXX miles on it. The original owner changed the SC pulley, but it doesn't have any identifying marks. Can anyone identify this pulley? I want to make sure I can order the right belt when Inspection II rolls around.

 

Look for a stamp for a reduction amount....
A typical 535 length, 6 rib belt from the local autoparts store will fit a 15% or a 17% fine....cost you $25 or so....maybe less.... At that price you could get a 532 belt too....fits a 17% better...see what fits better.....

 

I can tell you that its not like my Alta.

But it should use a regular belt, just the size smaller, that is correct for the 15% pulley.

 

I'm not seeing any stamping whatsoever. Where might it be? Is there any other way to tell what size it is?

 

looks like my helix pulley no markings on mine either. Just get the belt for the JCW or a 535 or 532 should work

 

He is correct that is a Helix pulley, looks to be a 15% pulley.

 

Thanks for the responses!

 

I am finishing up my tensioner & ATI install, and I've gotten to the point of installing my new belt. I got a 535, and despite every four-letter word I can come up with, I haven't been able to get it on. It turns out my old belt was a 539. Is the 535 too short, or am I being a wuss?

 

If your crank pulley is a +2%...the 539 might be right...
A 535 is doable (with a 15%, stock crank damper size)with somebody pulling back on the tensioner with the tool...simply locked In place the belt will be too tight...so have a helper pull back on it...should be able to thread it on fine.
A 539 should be fine though...might slip at higher rpms when it is a bit older...

 

I fought this thing for a long time yesterday. I had the tensioner tool in the second hole, and the belt was just too short. I ended up putting the old 539 back on so I could drive the car today. The ATI is standard size. Does this suggest the SC pulley could be something other than a 15% reduction?

 

Read my above post....
To get s 535 on...it usually requires a 2nd person to pull back on the tensioner...you can't do it when it is pinned....

 

try leaving the idle pulley last. you should be able to get it on even with the tensioner pinned in the second hole. a lot of people say you need help but i got my 532 belt on by my self by leaving the idle pulley last and walking it on. it took a little time but got it on.

just 17% pulley and stock crank pulley

 

You were correct, which seems to be awfully common. Thanks for the advice!