Roadster engine spins GM alternators too fast?

[ppeters914]

This is part of a response to my "fuses and fusible links" post:

I replaced the alternator with a GM part years ago, mainly to keep up with the stereo, .....

I'm on my fourth GM alternator, a good choice buying an Autozone lifetime warranty, because the engine spins them too fast. The small fan blades fracture and fly off. One fan blade disappeared, another one "found" the radiator hose. This most recent one I retrofitted with the Datsun pulley to slow it down. So far ............

I cannot believe this is normal, i.e. replacing the alt every year or so, otherwise no one would do this swap.

How about some comments from others with GM alternators?

Thanks.

[Dave]

One word...Autozone....

[itsa68]

Some alternators that are re-built, might have a pulley fan which has been blasted and cad plated. If the pully fan (or a part ) is not baked properly at an elevated temperature after cad plating , hydrogen embrittlement will occur in the metal.
The metal will fracture after a short period of use from the vibrations.

Ray B.

[spyder]

Two comments regarding my gm alternator exploits. #1, Yes ?autozone and #2 I spend a lot of time in the high rpm's. This car is not near stock but LOTS! of fun!!! It lets go when I,m close to my 8k redline. I think people who drive NORMAL should not have any problems. Lastly, I changed the pulley using the larger datsun pulley and I believe this issue is resolved.

DO IT!

[S Allen]

I have been running the same GM alternator for three years now. No problems. I drive with a spirited nature as well so no putt-putting for me. Any thing rebuilt had a higher than normal failure rate-not just alternators. I have run the GM alternator on all of my roadsters and never had one fail. Maybe it is just luck but so far so good.

Steve

[ppeters914]

8k rpm?? Oh, so you're one of THOSE people. Just kidding!

Thanks for the extra info. Not worried anymore.

Next step is to take a hacksaw to the alternator bracket. Checked at two local machine shops, but they want $30+. Ridiculous!

[spyder]

Yes I am and it scares the hell out ot the coffee can cars who pick on me! What hacksaw? IIRC, mine bolted straight on. The adjuster arm is a beeet close but it stops grinding real quick!

[ppeters914]

For the early (pre-1968) cars w/ the alternator on the passenger side of the engine, the lower alternator mounting bracket needs 1-1/4 inches cut off. See the instructions and pics at:

http://www.311s.org/tech/electrical/singlewire.html

The later engines need an additional plate, but no bracket cutting:

http://www.311s.org/tech/electrical/gmalthigh.html