Model 7127 GM-Style Alternator
- 10 SI series, 63 Amp, 12 Volt, Internal Regulator type
- External Switch Required
- Sold outright. No core charge!
- Remanufactured with new brushes and bearings, right here in Eugene, Oregon
If you plan to run your system near capacity for extended periods of time, we recommend replacing the standard pulley on the alternator with one of our Special Industrial "A" belt alternator pulleys (see details below).
Be aware, you must have a battery hooked up to an alternator or you will damage the voltage regulator if you try to rotate it at normal RPMs.
This alternator can be used with any of our generator projects:
- Direct Drive Coupler Generator Project
- Horizontal Shaft Belt Drive Generator Project
- Vertical Shaft Belt Drive Generator Project
Optional Accessories
Wiring Plug (New Style)
This molded wire connector is a replacement part for hooking into the two terminals (R and F) on the alternator. Switch for Alternator not included.
Alternator Pulleys and Belts
The normal 2.5-inch pulley on a GM 10SI or 12SI alternator is a 3/8-inch automotive pitch belt. You will not be able to find a 3/8-inch 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 and require Industrial "A" style belts.
The 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.
There is a better solution! The 2.5-inch Industrial "A" Belt Pulley for the GM 10SI or 12SI alternator.
We are now offering a special 2.5-inch Industrial "A" style pulley that fits the GM 10SI and 12SI alternator. This pulley will fit any of the alternators we sell, and we will install it for you at no cost by request. Shown at the left is the same belt as it would fit our new 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 ours.
If you already have your own alternator, or did not buy an alternator from us, we cannot guarantee this pulley will fit your alternator. Please look very closely at the diagram to the right 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 than the cost of the pulley.
Alternator Direction and Fans
The photo at left shows stock fans for 10SI (on the left) and 12SI alternators (on the right).
Most Asked Questions
Q: Doesn’t the alternator run backwards?
A: Yes, in several of these projects the alternator turns in the opposite direction. An alternator will function in either direction.
Q: Is cooling an issue when the fan runs in the wrong direction?
A: In most situations, no. The fan still functions but at reduced efficiency. The alternators in our projects are bolted to a metal mounting plate which acts as a large heat sink. We do offer a special bi-directional fan that can be used in place of the stock fan. This fan is as efficient when rotated in either direction.
Q: Where can I find a reverse fan?
A: A bi-directional fan is available from us! For a true reverse direction fan, you will find them used on '65-'69 Corvairs. But the Corvair fans have an integral pulley which cannot be removed and is not the ideal diameter.
Bi-directional fans (back face on left, front face on right) for use with our 10SI and 12SI GM alternators are available here at TheEpicenter.com. If you already have an alternator, we cannot guarantee these will fit. They will only fit if the existing fan has a dish in the center, and the dish points toward the alternator (see the picture to the right).