My alternator recently gave out in my 73 Z, so I ordered the MSA 60 amp upgrade kit.  I decided to give their alternator a try instead of sourcing one locally.  Of course they warned me it's made for 70-72 Z's, and additional work is needed for a 73, have a pro install it, no warranty, etc.

There are a  handful of threads here for a 73, but some with broken links, and some with unanswered questions.  Maybe this thread can be used to consolidate 73's.

From what I gather, for a 73:

• Install new alternator and connect per instructions.
• The regulator plug (Dave's) is the same for 73 as 70-72.
• Extra wiring is required if you are running an electric fuel pump. I am not, just the mechanical one.  Thread here for electric fuel pump wiring, with safety wiring.
• If the car has had the "vapor lock fix" or "electric fuel pump modification" or "V-3 modification" done to it, which added some wiring to a fuel pump relay.  I'm not sure if cutting off the "yellow wire" is needed only if the fuel pump relay exists.  I couldn't find a fuel pump relay on mine.  Is this step needed only for cars with the modification?
• Add an 8 gauge wire between the alternator BAT connector to the starter solenoid where the positive battery cable connects to.  

So here's the old and new internally regulated alternator, Dave's plug, and instructions, from MSA.

Here's the installed setup.  Seems to work fine.  My starter connection is getting a bit crowded with all the relay connections.  The Pertronix seems to be work better, but maybe it's my imagination.  Amp gauge moves a tiny bit at idle, and little more with hazards on.  

Anyway, I just want to make sure I'm good and won't burn my car down!  😏

Thanks!  

Ken

Okay, your car probably has the fuel pump relay modification. It looks like you have two wires at the starter solenoid.

There is no need to cut any wires! Just unplug Relay A.

The relay is located on the passenger kick panel. If the relay is plugged in and you have that alternator mod, you will run your battery down.

 

Okay, took some time to cleanup the relay bracket, some were screwed in the wrong location, and labeled them.   It looks like relay A is missing, but B is there.

This must be part of the fuel pump harness fix, goes out to the starter solenoid and fuse box/ignition.  The relay A connector looks a bit hacked.  Maybe I'll remove it altogether some day.  Battery seemed fine this morning, engine cranked over as usual.

Thanks for the help!

Ken

Based on your photos, I concur with your assessment. With Relay A gone, you have no problem with the alternator upgrade.

I also have a '73 with the 60 amp alternator upgrade as described above (with the electric fuel pump and wiring modification removed). It seems to work fine with the car actually charging at idle with the lights  on. My question is whether the 8 gauge wire between the alternator BAT terminal and the starter solenoid is necessary as it creates a parallel circuit to that running through the ammeter, essentially rendering it not useful.  I understand the rationale about minimizing current flow through the stock wiring if running large electrical loads such as radiator fans or a big stereo but with an unmodified car is there a benefit?Note that even with a 60 amp alternator the ammeter rarely indicates a charging rate of more than 10 or 20 amps even just after starting the engine, so I doubt that the stock wiring is operating beyond its design conditions.