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2/21/2021 11:12 AM  #1

250 I6 in 66 Mustang - Accessory Belts

The accessory belts were yet another saga.  I found that it would be best to have 2 belts.  A single belt would work but there was only a small amount of wrap around the AC compressor and the alternator, suggesting that these accessories might not work well when they were under load.  So I decided to use 2 belts.
The next step was measuring the belt lengths to take to the local auto parts store.  It turns out I need a 3/8” wide belt for both the AC and the alternator.  The AC belt is a Gates 7470 (47-3/4” long).  The alternator belt is a Gates 7420, 42-5/8 inches long.

 There was a side issue I encountered as well - the water pump pulley I had was a single sheave and I really needed one with 2 sheaves to make the two belts work correctly.  I searched for a pulley but was not successful in finding one. 

On a whim I pulled the water pump pulley from the 351 that was in the car previously (this same pulley was on the 289 that came in the car) and found out that it would work if there was a small spacer between the water pump flange and the inside of the pulley and if I enlarged the center hole in the nose of the V8 pulley. 

I made the spacer out of aluminum stock I had laying around and drilled out the hole using a stepped bit in the drill press.  It bolted up perfectly.

Happily, I have since found the correct pulley for the 250 I-6 and have installed that.


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