I think Ralph recommended one to me but I was doing oither stuff now I can't find that thread and the "new" one I put on last year is squeaking again after I changed the tensioner.

 

Goodyear Gatorback Poly-V belts.

Pricier than some, but well worth it IME.

RwP

 

Well the name has changed to Continental Elite Poly-V belts and they are as rare as hens teeth. At least I got Amazon to tell me the part number. 4070972 I also found some good data looking. Apparently these belts get glazed and then they glaze the pulleys. the suggested fix is to sand the pulleys then clean them with brake cleaner before installing the new belt. got away with belt dressing for a while then yesterday I tried some paraffin wax and it seemed to work. Today it screams nonstop lmao at myself. So I'll order the new belt I found it on eBay. While I wait I will clean the pulleys and try a wire brush and some belt dressing on the belt. It is also possible that there is a power steering leak or coolant leak wetting the belt and causing this problem..

 

Updating:
I took off the belt and cleaned the pulleys. I used sand paper in each groove, hard on the hand. Then I went over it with wire brushes and brake cleaner. I wiped them off with a cloth and let them dry out.
The Crank pulley was hard to get all round and I could only use my big wire brush on it. A lift would be handy in this case.
The grooves were very dirty especially on the power steering pump which also looked wet. I shined up each one.
I reversed the belt and sprayed it with belt dressing and bushed it with a small soft wire brush all the way round and let it dry completely. Once I replaced it no sound at all on starting. So I guess I'll have an extra belt once the Continental Poly-v gets in.

The Takeaway:
In future maybe clean the pulleys of all the built up rubber gunk before buying a new belt