'66 390 A/C PS

[Loren L.]

Page C4 of the C60 (A/C)AIM (probably outdated) shows a water pump pulley that is THREE grooved; the JG that I have (again probably outdated)NEVER mentions this pulley.
Anybody's advice is welcomed - a friend has such a car - responses that it is the ONLY ONE are not welcomed.

[Joe L.]

Re: '66 390 A/C PS

Loren-----

It's no mystery. Such a pulley existed and was used for 1966-67 L-36 applications with C-60. It was also used for most 1968-70 big block applications. It was GM #3889372. It was replaced for SERVICE in June, 1971 by GM #3995644. That pulley has been discontinued for quite awhile.

Most folks don't think that any C1 or C2 Corvettes ever used a 3 groove pulley for anything. Their almost right, too. The exception is 66-67 L-36 with C-60.

[Loren L.]

Well, I guess it was a mystery to those

on my version of the JG - admittedly, I think, outdated.

[Joe L.]

Re: '66 390 A/C PS

Loren------

So, why was this pulley used for 66-67 L-36 with C-60 applications? My guess is (1) because the extra pulley groove was required for the A/C compressor and (2) because its smaller OD (5-1/2") increased the fan speed and provided for increased cooling airflow. I think that's also why its use was expanded to most big blocks, with or without C-60, for the 68-70 period (68-69 used the third groove for the AIR pump).