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

546 Views 12 Replies 8 Participants Last post by  PSIG
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. https://www.summitracing.com/parts/TFF-7771

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Yes, just fits. I did reclock it for better wire access.
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This is very timely info for me as well. I'm getting ready to do final assembly on my 390 build and this has been one of the nagging questions.

Thanks guys!
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Has anyone put a 3G alternator on a 390 in the high mount position?
Yes, I have. Yes, it fits. Yes, there are multiple 390/FE brackets, and I have not tried them all, but should position the alternator at the same position with any of them, in order to align with pulleys.

Important - I use the short-ear 3G alternator for most things, as it has the same mounting bolt locations as the 1G and 2G it replaces. Other versions (Taurus, F-150, etc) have different spacing, and not recommended. An easy lookup for the parts counter or online shopping is 1995 Ford Mustang - any engine. There are others, but that one always gets the 130A short-ear version.

Any short-ear will do, and the difference then is the clocking of the rear case for wire access. Changing this is simple and there are many online references to do so. They also come in various flavors of voltage regulators, but none with concern, such as "soft-start". Shopping today will find them new from under $100 to the moon, or at the wreckers from about $20 with warranty, and a free test at any auto parts store. I suggest using stock (not 1-wire) for best operation and regulation. Wiring is simple, and if you can do one wire, you can do two, for better results. :cool:

At the bottom is a PDF article I wrote about it... OMG gaining on 20 years ago. :oops: It includes multiple 'fixes' for stuff you may run across (or not), and I'm adding the basic for-anything wiring image as well. I also have the earlier generator conversion wiring diagrams if anyone needs that. Hope that helps!

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as a side note, my brackets were original as well, the long arm one has been extended a bit though, but not to clear w this alternator. I also tapped and installed a helicoil on the top hole of the alternator housing as its not threaded, but a nut on a longer bolt will work as well. .02
This thread sent me down a rabbit hole. Now I’m considering of swapping to a 3g on everything.
I've done this conversion, works very well. Especially if you are using electric fans or similar.
Higher AMP alternator needed for that. Also, if one goes bad, can easily replace at most parts stores.
I found these links to be very helpful:

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Great information in this thread—thanks! I’ve been hesitant to do this swap because some folks complain about an annoying belt whine during startup. Is that not an issue for you all?
No belt whine on my setup. The tensioning is vitually the same as a 1G alternator, especially if you re-clock the alternator to move the connectors for easier access.
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me either. was basically a drop in mechanically (yes i also clocked mine) i wonder if the 'whine' issue is on refurbed ones that may be kinda crappy or pull a part ones? just speculating.
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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.
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