3G Alternator Hints

[lanky 44]

Today I started installing a 130amp 3g alternator with the 7" ear spacing. I read everything I could before starting and thought it would be a drop in with some straight forward wiring. 

Here is my $.02 for those with a '69 and with a 351w. These cars have different alternator brackets from all other years I understand.

You WILL need to fabricate an intermediary bracket for the lower mount. The 3g case (specifically the 8mm bolt) interferes with the cylinder head alternator mount bolt, the one on the right side. It interferes to much for an easy fix. This means that the alternator can't swing far enough towards the lower bracket for the bolts to go in (even though the spacing is correct). This also means your old belt won't work either. I'll save you time and let you know that the intermediary bracket should have its holes 3" apart center to center, and it should be thick steel like the factory brackets (~3/8" thick I believe). You will need to either make or find a spacer to take up the extra depth created by the intermediary  bracket to keep the pulley straight.

My last advice: don't bother messing with clocking the alternator case differently for 2 reasons. It's difficult to do (I gave up after doing exactly what I read other people did) AND you can break the aluminum case. It's nearly impossible to do without marring up the aluminum. One more reason not to bother is that if you do need to get a new one for a late model at the regular part store, your wiring would be setup for how you clocked it and not how they are when you buy one. Hope this saves someone some time!

[Mach1 Driver 560]

pictures would help if you've got em

[MN69Grande 203]

This is interesting.  I did the 3G on a 302 and didn't have any of these issues.  I used an Alternator from a 90s Windstar I think.  The only change for me was I had to use a bolt and nut on the lower alternator/bracket connection because the new Alternator didn't have a threaded hole.  Instead it was smooth so I got a longer bolt and a nut and it worked fine.  Which alternator did you get?  I read somewhere DOHC late 90s Taurus alternators work well (I only see the Sable below).  The one I got for a Windstar worked well.  I'll post a part number tomorrow.

 

From a Stangnet forum- https://www.stangnet.com/mustang-forums/threads/3g-swap-these-the-basic-steps.866228/
Here is a list of vehicles that have the 3G alternator, most are 130A, but some might be 110A:

94-96 Mustang 3.8 V-6
94-95 Mustang 5.0
94-96 Thunderbird 3.8 V-6 (non SC)
95-96 Windstar 3.0 V-6 (most are 3.8's)
93-96 E/F series Trucks/Vans 4.9 L6*
96 Sable 3.0 V-6
94-96 Cougar 3.8 V-6

*Probably the best one if you can get it (should be easy to find, too) is off the E/F series...this series uses a threaded top ear like the stocker on the Mustang....E/F series with threaded ear uses metric bolt. ALSO, make sure the E/F series is 130 Amps and NOT 95.""

That last note probably explains the change i needed. 

[1969_Mach1 333]

I think lanky is talking about the alternator case interfering with one of the bolts that attaches that cast iron "T-shape" bracket to the cylinder head on 1969 351W motors.  On the alternator it's one of the three lugs for the long small diameter thru bolts that hold the alternator case halves together that's the problem.  I had that issue on mine.

To work around it I first attached that "T-shape" bracket with small headed bolts.  I had some ARP bolts with smaller than normal head sizes.  Then on the alternator I was able to trim a little off of that lug that caused the issue.  I simply masked off the alternator so no shavings would get inside.  Then used a hack saw and files to trim off some material.  On my 3G alternator the holes for those three small diameter bolts had countersinks.  So all I could do was use an appropriate side drill bit and recreate the countersink as best possible.  If I were to fix it again, to get more clearance, I would start by using button head Torx bolts to attach the "T-shape" bracket to the cylinder head.

[lanky 44]

1969mach: exactly! I wasn't expecting this problem. Today I fabbed up a simple extension bracket to span the space between the lower mounot and the alternator case, so that my alternator is unchanged. 

[lanky 44]

I got the 3g up and running. I used the common diagrams on the Web and it worked out great. Steady 14.30V to 14.35V in all conditions. When more amps are drawn, the voltage dips for just a moment and then gets right back to that range. My blower fan no longer changes speed on the high setting from idle to the car moving like it used to.

Once I have more of it all buttoned up I will take some pics to show how I mounted everything. This really has me wanting to swap the battery to the trunk soon! I love that I can now go to any parts store and buy a replacement easily...or the junkyard on half off day...