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Will 3G alternator fit in stock position of 68 galaxie with FE 390?

948 Views 14 Replies 8 Participants Last post by  808Mark
Has anyone put a 3G alternator on a 390 in the high mount position? I'm really tired of my fitment issues i'm having with my GM10SI case. The bump on the back hits the head of the motor. I'm not interested in going to the low mount style as i'd like to use the original brackets as much as possible. I measured from my bracket to the block and its extremely close to if not slightly more than 4.5 inches. The dimensions off of summit say from the mounting surface to the back is 4.5 inches.


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I do. it fits, way better than the tuff stuff 1-wire i had, zero issues. yes in the same high mount passenger side position. this one, with a single groove v pulley.

View attachment 176063
Thank you guys for the advice! I was able to reclock it and wire it. Wiring wasn't too bad really, and I like that there's a wire for the electric choke. Plus I was able to remove my diode as the 3G doesn't have the run on problems like the GM 10SI. I'm really happy that I did it and could use my original brackets!

The only thing that worried me a bit was the back of the alternator is touching the block. I'm thinking it could overheat?


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No single v-belt squeal on mine either, but I tension mine properly, and the pulleys are good alignment, no wear or visible surface waves, etc. If your belt squeals, you are glazing the belt, and it will continue to squeal after that. The belt is done. The condition of the pulleys is critical, along with a fresh belt, and don't try to start it loaded with a jump or low battery as it may overpower the belt trying to quickly recharge a dead battery.

Belt break-in is 10-20 minutes on a new belt, and must be re-tensioned again after that. Even the factory had single-sheave pulleys on certain early V-belt 3G models, so it should be fine normally, and when set-up properly.
Do you have the displacement specifications for the belts at 10 pounds? I'd like to check mine as well, but gave up when I read into how many variables go into calculating it ><
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