Andre, your equal diameter pulley is definitely wrong, I thought you already understood that.
The '64 water pump pulley is definitely consisting of two grooves with two DIFFERENT diameters.
Not only do I know this to be true, but you can confirm it by the illustration.
Look at the middle left and the bottom right illustrations.
They represent the two A/C applications, with or without PS.
The same Water Pump pulley is provided for both, item 13 & 28 respectively, both require p/n 544594.
Compare how this pulley is illustrated with the illustration bottom left for the two groove pulley used for PS without A/C, item 22. This pulley has two equal diameter grooves.
It is illustrated with a single circle.
But the water pump pulley for the A/C application, because it has two different dia. grooves, is illustrated with TWO different dia. circles.
That follows standard engineering graphics convention.
The 1/2" wide belt for the A/C drive is circumstantial evidence to prove the front groove must be wider than the rear groove.
I initially thought that needed evidence to prove. But W.E. correctly points out that a 5/16" deep belt (the depth of the '64 A/C drive belt) would barely drop into a 3/8" groove. I confirmed that by calculation, TAN 18 deg=.3249=.0625/x, x=.1924", just more than 3/16". The belt angle is 36 deg. The calculation is determining the ht. of a trapezoid with parallel bases of 3/8" and 1/2" length. The 1/2" belt will only drop into the 3/8" wide groove to the point where the belt is 3/8" wide. That forms the bottom of the trapezoid. The top is the width of the 1/2" belt.
18 deg is half the belt angle, .0625 means 1/16" overhangs to the right, 1/16" overhangs to the left. The ht. works out to be 0.1924" which is a hair more than 3/16". The total belt ht. is only 5/16", so less than 1/8" is down in the pulley groove.
As I point out, the belt listed in the illustration for the '63 Tempest V8 is 17/32" depth. It would be 11/32" down in a 3/8" groove and this corresponds well with the 5/16" which seems to be the target depth.
That is why I suspect that they may have had a two groove pulley with both grooves 3/8" wide in '63. Putting a 17/32" deep 1/2" wide belt in a 1/2" wide groove likely wouldn't work because the groove isn't typically all that deep. Putting it in a 3/8" wide groove would be okay.
But the '64 specified the 1/2" wide, 5/16" deep belt. It had to run in a 1/2" wide groove, no way would 1/8" down in the groove be acceptable.
If you are running 3/8"wide belts, I'm curious about the balancer assembly you are using, is it the '64 A/C unit or something else? If the '64, a 3/8" wide A/C drive belt will be down in the groove. I don't think that is recommended, but not sure what harm it would do.
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