[kleen56]

I'm running a 10SI alternator on my vehicle which is running hot during the hot weather days. Does anyone know if the larger cooling fan on the 12SI model alternator is interchangable with the 10SI for additional cooling?

[302 Z28]

How do you know your alternator is running hot?

Vince

[kleen56]

Vince, we've been having 100+ temps here in CA. Whenever I go out to a show or cruise in the high temps, after a while of driving, the alternator will shut down and stop charging until it cools. I spoke to a few buddies who have the same problem with the 10SI type alternators. I guess they are notorious for overheating and thats why the improvement with cooling fans came about with the 12SI model. I also have the alternator mounted near the passenger side head and exhaust headers which doesn't help with overheating the alternator either. I should probably mount the alternator higher up above the intake, I just don't like the looks of it there. Since the 12SI alternators have little or no overheating problems, I was wondering if the fan which provides cooling would be interchangable. It would easy to do, or go with a 12SI alternator altogether. (mine is chrome and looks purdy). I also heard that overheating an alternator will kill it quickly. Trying to avoid it. I've opened my alternator several times, and everything appears to be and checks out OK. Only acts funny in really hot temps, otherwise, no problems.
Ed

[302 Z28]

I have a 10SI on my 34 and I live in North Texas we have also been having temps in the 100+ range. I have not noticed my alternator shutting down due to over heating. Of course mine is mounted above the intake manifold. Mayby you need to decrease the pulley size in order to speed the alternator up for better fan draw.

Vince

[ericnova72]

Kleen, we ran into this with the CS-140 alternator we used as an upgrade on a '67 Elky street/strip car. The alt was mounted just slightly lower (1-1/2") than the factory position in front of the pass side head. As the alt pulls air through the case from back to front(dumb idea, should be the other way around IMO), it was sucking up the hot air off the head and header tubes and dropping out until it cooled off. Our fix was to fab up a polished aluminum shield bolted to the head behind the alternator that extended out and partially back and over the front header tube at the valve cover rails height. Problem was solved.

[kleen56]

Originally Posted by ericnova72

Kleen, we ran into this with the CS-140 alternator we used as an upgrade on a '67 Elky street/strip car. The alt was mounted just slightly lower (1-1/2") than the factory position in front of the pass side head. As the alt pulls air through the case from back to front(dumb idea, should be the other way around IMO), it was sucking up the hot air off the head and header tubes and dropping out until it cooled off. Our fix was to fab up a polished aluminum shield bolted to the head behind the alternator that extended out and partially back and over the front header tube at the valve cover rails height. Problem was solved.

Great info Eric. I suspected my overheating was from the engine and headers as my alternator is mounted right in that position with the back of the alternator no more than 1 inch from the engine. Anyways, just to update and maybe have some helpful info for Vince.(302 Z28). I went to a alternator rebuild place and they sold me a fan blade from a 12SI alternator for $5, it's definitely bigger and draws more air to the alternator. The fan fits right on the shaft and is inter-changeble with the 10SI alternator. I put it on, and so far so good. I hope it solve the problem with this fan blade on and it's a easy change to do, I'm opting for the plate on the heads or moving the alternator higher up and away from the heads. Thanks guys for the great info.
Ed