I removed the original alt. today, and replaced the regulator. Someone once mentioned that the more copper is wound inside "the cage" of the rotor, the higher the amps. If this is so, what would I specify at the Auto-Zone. The clerk showed me a 78A, but it sure looked like the less than full windings on my 66A unit. I tried to install an antique 100A monster from a late 70's Full Size wagon. The heater hose housing/outlet is in the way of the upper bracket. It did fit on my 305 though. I need the higher output as I plow snow. About as hard as one could tax a charging system. :help2: Any advise?

You could try finding an alternator and bracket off a Military Truck. They are the Large frame 100 amp, but in my opinion they are alot different than the higher amp small frames. I think they are setup to run 100amp continuous and not care one bit. Only difference you will notice, is you will have to connect a ground wire to a stud on the back, as they have an isolated ground to work in the mil 24v system. Each alt is only 12v.

Any junker have one to donate? I'll be off to the local starter shop this AM, we'll see what he has... ;)

check with brian at www.brtruckparts.com explain what you are after, and he might be able to help. Tell him I sent ya (bought my blazer from him)

Autozone talked me into installing a 94Amp alt. when my 78Amp one failed on my 86. Big mistake at least if you have a V-belt. A serpentine belt may work fine, but not the V-belt. I had to continually tighten my belt due to the higher amperage load stretching the belt. I was on my third belt by the time I got home from a 14K trip. One broke in Nova Scotia and one broke in Virginia. I replaced the 94 unit with a 78 one after I got back home and I have not had any problems with squealing, stretching, and breaking!!!!!!

I agree to an extent, keep in mind, the setup I am talking about was used by the military for a long time...... I would think that there wouldnt be much trouble with it. I have put over 3k miles on mine without any trouble on the belts.

Autozone talked me into installing a 94Amp alt. when my 78Amp one failed on my 86. Big mistake at least if you have a V-belt. A serpentine belt may work fine, but not the V-belt. I had to continually tighten my belt due to the higher amperage load stretching the belt. I was on my third belt by the time I got home from a 14K trip. One broke in Nova Scotia and one broke in Virginia. I replaced the 94 unit with a 78 one after I got back home and I have not had any problems with squealing, stretching, and breaking!!!!!!
cougarjohn, where you using the skinny v belt or the better wide belt? had same trouble with mine, squealing, stretching, no charge. then i found out there was a wider belt available. no more squealing.

alternator still dont want to charge at times though, but not as bad. its not that old..so i have no idea....

I use the standard V belt that is made for it. I just checked my spare new belt in the truck and it is a Kelly-Springfield 15480. The package states it is 15/32 in. wide. If there is a different one then I would be glad to know. I have 31K miles on the current belt since I changed back to the 78Amp unit and it is still good. I can understand how a serpentine pulley could hold up to the higher amps, but my V-belts sure didn't. The Gates belt that I installed in Nova Scotia failed after about 2,000 miles which isn't much!!!

cougarjohn, try this. A GM line mechanic filled me in after i tried to get a hmmwv 4 grove water and crank pulley to fix my slipping alternator belt. blew up an alternator before I knew...and have been using the new belt on the truck about 5 months now, its a big difference. its a tad shorter so its a bit tight at first(to get on the pullies)..but once broken in..its golden.
15/32 looks like 3/8 to me, so looks like you might have the standard belt. there was the standard, then a preferred belt which is 7/16. you have to ask them for the preferred, they wont give it to you usually without mention. i got mine at napa. yes I know there isnt much between 3/8 and 7/16, and the gm mechanic admitted it. but there is a major difference on my truck.
these are napa part numbers but its a gates brand they gave me:
standard belt 3/8 :NBH257480
preferred belt 7/16:NBH5725

once its been broken in and retightened, no more slippage. seems like much more of a beefer belt to tighten as well. with the old one, I was retightening it so many time i stripped the threads on the alternator. had to put a bolt and locknut through so now takes 2 people to tighten, or someone with 3 hands...
if it didnt cost so much, Id still go dual belt alt with the hmmwv 4 groove crank and water pullies.
hope it helps.

I think I must have the larger belt since 7/16ths is only 14/32nds versus my 15/32nds. Mine is hard to get on when new and I put the top bolt in after I get the belt on. Usually the last three numbers of a belt indicate the length of the belt, i.e., my 15480 belt is 48 inches long.

I think I must have the larger belt since 7/16ths is only 14/32nds versus my 15/32nds. Mine is hard to get on when new and I put the top bolt in after I get the belt on. Usually the last three numbers of a belt indicate the length of the belt, i.e., my 15480 belt is 48 inches long.
both belts I mentioned are over 48" long. sounds like your belt is actually a little wider then the one Im using. even now, my alt doesnt charge at a rate it should at times and i doubt anything is wrong with it. but it doesnt squeek anymore. its a 78 amp by the way.

if you really are using the widest belt possible, and want that higher output alternator maybe you should look into 2 groove alt pulley or going serpertine conversion. the 2 groove alt pulleys are readily available. Ive even seen 3 groove. its the other 2 pullies thats a pain to find, but not impossible.

I think if I really rquired the 94 Amp alternator then I would change everything to the serpentine pulleys It would be expensive since I would need a new crankshaft damper plus new pulleys on everything. I used the 78 Amp unit for 16 years without a problem so I was happy to go back to it and get rid of the the problems.

Yeah forget all that. im sticking to the 78 as well after hearing your story. i just have to figure out if my belt is still stretching, or take the meter to the alternator to see if it really is putting out correctly on high load.

double belt alternator would be cool though....