Originally Posted by CHEVYRODS
The original belts and pulleys were working just fine on the engine when you took it out. This deal about the having to be same size pulleys is just crazy. There is a purpose on a factory application for the reduced size pulleys. . I'm sure you can find a picture on the net of your exact engine and I will bet you it won't have all the matching pulleys. Somebody has been shopping at speedy Bill's and Jegs to much. Large and small pulleys work just like gear size reduction and speed of what it turns.
This is about as crazy as the comment about one belt turning one way and the other one turning the oppisite way. Lets see a picture of how you come up with that one.
If you are only running a alternator and PS pump both the pulleys have to be the same size. The crank pulley drives both of them first. If you use the smaller pulley in back the water pump pulley wants to run at 2 different speeds. It's a fact there is a night and day difference when you have the right size pulley on the water pump.