So I bought the WAI 24-83100 double alt pulley that's off of the chrysler mini vans.

http://foxed.ca/RX-7/WAI%20PART%20DESCRIPTION.pdf

When I got it I noticed that it will put the belts closer together than the water pump and crank do do to the smaller space between the grooves. I stuck it on anyways and got two new belts of the same brand. The inside belt runs true but the outside one was at a slight angle. Fast fwd 800miles and it's screwed up the outside belt and is (till I took it off just now) running on an / inside that outside groove on the alt. with rubber grindings all over the front of the engine.

So? I know more people have had this issue. Has anyone NOT had this issue with both belt backs almost touching on the alt pulley? Is there a brand where the belt backs are not so close?

I'll have to go the 3L220, L322, NBH257215 belt option if I can't figure this out.

For eg:
Here is my setup before it started to show wear:

 

I don't know about that pulley, but I have an aluminum one bought from a vendor that used to be on the forum. I finally found some some belts at Napa that were matched, and narrow enough to sit further down in the grooves so there wasn't so much rubber grinding off.
Being for a Chrysler van may be your problem, though I've seen posts on here stating you can use pulleys from other vehicles.
The one I bought was for a 2nd Gen, but seemed to work fine on my 85 12a.
If I remember, or you remind me, I'll dig it out and measure it with calipers if you like.

 

It wasn't the top grinding off really, more the inner side of the outside belt, never the less I'd like to find out if yours has a different spacing.

You'll see the drawing and specs on this one here

http://foxed.ca/RX-7/WAI%20PART%20DESCRIPTION.pdf

 

You can get the correct double-pulley for your application for like 16 bucks from www.re-speed.com

Not sure if you want to buy yet another part, but if you want to be sure this mod is done correctly it may be worth the extra money for the peace of mind it will bring.

Good luck.

 

I haven't had that problem with the mitusbishi dual pulley, the grooves on the pulley are spaced a little more tightly than on the main pulley but not enough to make a difference in my experience.

Here's some photos of my set up, which has been doing fine since I put it on about two years ago, no belt wear, no problems:





And here's friend Mike's more recent set up with prettier belts, he hasn't reported any issues either

 

I ordered one and got an email today saying they are out of pulleys until the end of the month. However, a new pully for 17 bucks instead of junkyard hunting...worth the wait.

 

I have been using the same WAI pulley for two years with the dayco top-cog belts. No issues.

 

Anyhoo, here are the measurements I came up with.

 

Thanks for the replies guys, I'm out of town for a bit so it is harder to keep up on things. Well it's great to know that that pulley has proven it works without belt problems. I guess my belts were just a little different sizes and that would make one spin faster and then chew off the one on the slight angle. I'll try it again with another set of belts.

 

Thanks for doing that for me, that one would be straighter all right, but being that I'd have to deal with the cross border shipping wait and extra cost I'll give my setup another go.

Do you guys think that you'll get waterpump slip with a single belt and an e-fan? 2 is safer and that's what I'm going to keep trying for but who has one belt and an e-fan with no problems?

 

You don't need two belts when running an e-fan. Heck I've run one belt and a clutch fan with no problems.

 

I'm running 1 belt and a clutch fan. No squeal.

 

Isint the point of having a dual seath pulley on your alt supposed to reduce engine rpms protecting the alternator from burning out? I burned out my 1st gen alt and now having a tough time getting the pulley off my replacement because It wont come off. Tried vise grips and a wrench today with no luck, now its soaking with deep creep overnight wish me luck tomorrow.

 

I've got an FD Double Pulley on my Isuzu Alternator and it works great. I just spaced it out properly to line up in the belt lines. Spacing on the pulley was already done for me.

AKA, Mazda setup the pulley width already. Dodge aparanetly had a different width in mind.

Do as above, get the right pulley. Cheap!

 

Why not upgrade?

Switch over to the 100AMP FD alternator and my pulley?

Link: https://www.rx7club.com/1st-generation-rx-7-1979-1985-parts-101/brand-new-dual-belt-pulley-fd3s-100amp-alternator-upgrade-860871/

Upgrade all around..

 

^That's how I solved my problem. The pulley's from Japan2LA are perfectly sized. I haven't had a problem with the belts since I put it on several months ago.

 

+1. His pulley is the best. Lightweight aluminum too, the minivan one is steel.

Also it's the correct diameter for an FD alt. The minivan one is larger which slows the alt down.

 

I figured it out.

24-83100 is for metric belts and the RX7 takes standard automotive belts and even though they don't look different in groove angle they are.