GM ALTERNATOR CONVERSION
  

Now that the stock alternator has bit the dust it is time to consider replacing the alternator with the stock unit sitting on the shelf, or converting to a GM single wire alternator to provide sufficient power for the new sound system also sitting on the shelf and ready to go in.  I chose to install the GM alternator conversion.  After studying the articles on 311s.org I went to the local wrecking yard and picked up a 63 Amp GM alternator, with pigtail, for $20.00.  I am told it is the same physical size as the 60 Amp alternator described in the 311s high windshield article by Erik Smeby.

I plan to connect the output of the alternator to the harness wire originally connected to the high current output of the original alternator and use the "S" Brake light bulb as an idiot light for the charging system.  This installation option will allow me to continue to use the dash ammeter.  When I build the new center console I will include a voltmeter to monitor the charging system.  
 

I purchased a right-side alternator mount a couple of years ago, so that would not be a problem.  The next step was to figure out the distance from the front of the alternator mount to the alternator mounting ear.  Once that distance is determined I will trim the black tube shown in the pictures to the correct length and install a long bolt to secure the alternator to the engine mount.

As luck would have it my right-side alternator mount is nowhere to be found, but I notice that the smog pump mount is still on Mr. Hyde's original engine sitting on an engine stand.  Not only is this a good find, I can engineer this modification on an engine outside of the car where it will be a whole lot easier to get at things to look at them and photograph them.
 

Original Smog Pump Mounting Hardware

The first step in mounting the new alternator was to shorten the alternator mounting adaptor supplied by GM with the alternator.  The final length of the adaptor is 57.8mm, or 2.27".

After trimming the alternator mount adaptor to the correct length (about 57.8mm, or 2.27") to align the belt I found that a 7.5" long, 5/16" diameter bolt will be needed to attach the alternator to the original smog pump lower mount.  Wink's Hardware only had this bolt with a carriage head, which I did not see as a problem for this application.

A rough measurement of the fan belt length indicated either a 38 or a 39 inch belt would be needed.  I tried a 38" belt and found it to be very difficult to install.  It did give me a wide range of tension adjustment.  The 39" belt goes on very easily, but only leaves about 1/4" of additional adjustment after tension adjustment on the setup engine, and no additional adjustment when the alternator was installed in the car.

To deal with the V-belt tension adjustment I turned to an original alternator adjustable brace.  I cut it apart about 1/4" from the round mounting hole that mounts to the engine.  I welded in 3" of additional length and used the slightly longer adjustment range to permit a wide range of adjustment using a 39" V-belt.  Removing or installing the V-belt requires removing the top bolt from the alternator to increase the range of movement.

After aligning the alternator pulley with the two other pulleys I measured the distance from the timing cover to the front smog pump brace plate.  The distance was about 25mm, or 1".  I purchased two new 8x1.5mm thread bolts, 120mm long.  These bolts required cutting an additional 3/4" of thread on the shaft and cutting about 3/4" off of the bolt threads.  For spacers between the front brace and the timing cover I used 3/8" ID aluminum thick-wall tubing.  The final spacer length was about 21mm. 
 

Now that the mechanics are completed I turned to the wiring.  The GM alternator has three connections.  The high current output, sense input, and excitation through the idiot light.  

Since I was choosing to use the ammeter in the dash I wired the high current output lead to an inline fuse holder with a 30 Amp fuse installed.  One side of the moisture resistant fuse holder is connected directly to the high current output of the original alternator, and the other side of the fuse holder is routed along the wiring harness located ahead of the radiator through 10 gauge stranded wire to the original alternator output wire on the left side of the body.  

The sense wire is a large diameter wire on the two wire side plug.  This wire can be connected directly to the high current output terminal on the alternator, or to the positive post on the battery.  I chose to connect the sense lead to the positive post on the battery to make sure the battery was charged at the correct voltage after any voltage losses in the wiring harness.

The excitation wire was connected to a switched battery source and connected in series with a # 53 12 volt lamp.  The next time I remove the dash I will replace the S-Brake lamp with this light.  For now it is tie-wrapped up under the dash.  
 

 
Leece-Neville Alternator Application Guide - About 1960