I just picked up a dual alternator pulley from the RX7world ebay store. I'm having a problem with it squealing slightly above 4000 Rpm or so. I bought brand new OReilley belts. The cheap $4.99 ones. Normally they work ok. I've tried changing tension from soft to tight and no change in squealing.

Could it just be cheap belts? Should I try putting a washer behind the pulley for spacing? Belt dressing?

I had an REspeed pulley on my 79 and had the same problem to a lesser degree.

 

Does the pulley run true? Might bent or crooked, that will make it squeal.

Are both belts the same tension? If not that means they are slightly different lengths. One will
squeal.

You can try belt dressing, if it helps then the belts probably differ in length slightly.

 

We have our Dual Belt pulley with matched belts, we also have an Adjustable Tension Alternator Bracket kit. This allows you to adjust the tension to the proper level. Pulleys & Belts (86-91 RX-7)

 

Dual alt belts should never squeal. If they do, it means your clutch fan is done and needs to be replaced.

 

I kind of figured the fan clutch was going... Makes sense as it would add load to the belts. Know where I can get one for my 80? (Mazdatrix is the only place I remember selling them as new... for like $250)

 

I'm sure someone around here has one for cheap. Most tend to upgrade to electric fans anyway. Not that it's always a good idea though. It depends on your setup.

 

I feel the mechanical fan is more reliable. The electrics could quit working at any time and overheat.

 

This thread has been very in lighting. My 1975 REPU has a dual belt pulley and it has always squealed above 3000 rpm. Now I'll be swapping out the clutch fan.

 

My REPU clutch fan did that so I got a dual sheave pulley. Still squealed. So I tossed it and got an electric fan. I felt a power increase. Yep the old clutch fan was locking up hard and stealing power.

The electric fan didn't cool as well as I would have liked so I eventually installed an new FC waterpump with a matching good used clutch fan so I could use a Camden. The electric fan went into my FB and seems fine there.

 

Always buy the matched set. After oreillys thinking i was stupid and gave me 2 of the same belts thinking that would work (half inch difference between the two) i went to napa and their matched set was perfect. But i also have efan. Main pully waterpump and alt.

 

OK I'm kinda haven the same problem I'm new to this site and new to the rx7 world. I brought a 90 rx7 very off my close boi car ran good until the belt snapped l, looked old to I replaced it with one from autozone drove it for a Lititle a snapped that one to.so it the stock pulley's the alt starts to squeal and then brakes the belt I went throw 4 belts, I order a alt with a dual pulley on it. It starts to squeal also then snapped both belts. But the funny part is the volts seem to be fine, but it get funny when it comes to this, the only way the alts squeal if the battery terminal's are connected but once I take the negative or both off the squealing stops and I can run the car fine but the battery is not connected I been stuck for two weeks please HELP!!! THEY are auto zones belts don't know if it matters

 

First off its hard to understand/read what you just wrote. Sounds like you have a
different issue. Also this is the 1st gen section and the 90 would be a second gen.
You should start a new thread in the 2nd gen section.

 

If i remember correctly... the fan clutch ended up being the problem.