BOOT77

What is the diameter of an 88-91 water pump pulley? Looking at March performance they have two sizes it looks like, 84-87 & 88-91. Of course NOT the LT cars, just the sbc gen1 cars. I have an 86 and it's in storage so I can measure it later. I am aware of underdrive and overdrive ratios, their effects and know what I want. My car only has PS, WP, alt with the correct rotation pump for my belt routing.

I would like to know why there was two size/diameters used if anyone knows.

WVZR-1

I don't have an early or later to measure for you but I'd think the 'reason' is/was the change in '88 to the 'denso A/C compressor. If someone wanted to accommodate you with a measurement an early should be stamped 14081087 - (CAU) maybe also. The '88+ pulley would be 10105209