Alternators... 140mm v 150mm... 78a v 108a

[efialtis]

I have an '84 K10 6.2L and am having issues with the Alternator. I had it tested by Checker Auto, and they claim it is OK, but my guage says that I am getting less than 13 v during operation.

I figure I could just replace it, and see what that does, but I found that there are 3 different alternators for this machine (2 actually, but read on...)

There is the 140mm that produces 78 amp.
There is the 150mm that produces 108 amp.
There is another one (unknown size) that produces 94 amp.

What I would like to know is WHY?
My Diesel has 2 batteries, so why do I currently have the 140mm installed?
Wouldn't the 150mm be better as it produces so much more power?

Would it be easy enough to install the 150mm? What kind of modification would I need to make, just the upper bracket?

Has anyone done this?
Are there other issues to worry about?

[DmaxMaverick]

The 140mm 60/78 alternator is fine, if you aren't running a bunch of accessories (like a plow, winch, BIG audio, etc). It charges the batteries just fine. If you want to install the 150mm, all you'll need is the upper bracket. You may need to upsize the belt, if there isn't enough adjustment. The adjustment slot bolt may be different, but no biggie (hardware store item).

If you want a high output, you can get ultra high outputs from suppliers (I'll look them up, if you're interested), in the range of 200+, in the 140mm housing. Very nice, and not much more $, if any, than a good parts house reman, and less than a GM dealer. Very nice!

[HammerWerf]

Don't forget to upsize the wire from the Batt post on the alternator to either the starter Batt lug ( stock wiring) or an additional jumper to the Pos on the nearest batt. Increasing the output of the alternator (increased amps) generally overwhelms the stock wire, causing the fuseable link to melt down. And use a wire of some stoutness. My 83 CC has a 94A SI 12 installed, and went though a couple of stock wires before a larger wire was put in its place.

HammerWerf