Special 2.5-inch Alternator Pulley
We are now offering a special 2.5" Industrial "A" style pulley that fits the GM 10Si alternator. These special pulleys will fit any of the alternators we sell. If you already have your own alternator, or did not buy it from us, we cannot guarantee this pulley will fit your alternator.
The normal 2.5" pulley on a GM 10si alternator is a 3/8" automotive pitch belt. You will not be able to find a 3/8" automotive pitch pulley to go on your engine. The only commonly available pulleys available in standard engine shaft diameters that have key ways are Industrial "A" style models. These require Industrial "A" style belts.
The standard pulleys and belts we sell to go on the engine are industrial "A" style, 1/2 inch wide. Although the combination of automotive and Industrial "A" style belts is not the ideal solution, it works well for most customers and is the least expensive option. The belt rides a little higher in the alternator pulley, and at the correct depth on the engine pulley. Extreme power users may experience some belt wear, especially if the belt is not tight, or if the pulleys are misaligned even to a slight degree because of the reduced contact area between the alternator pulley and belt side.
The Special Industrial "A" Belt Pulley is recommended if you plan to run your system near capacity for extended periods of time.
Shown to the right is the same belt as it would fit the special alternator pulley. So, for people who plan to run their systems near capacity for extended periods of time, we recommend replacing the standard pulley on the alternator with one of these special pulleys.
If you already have your own alternator, or did not buy it from us, we cannot guarantee this pulley will fit your alternator. Please look very closely at the diagram on the left for measurements. You may return it if it doesn't work out, but you will be responsible for shipping costs BOTH ways which may be more then the cost of the pulley.