This one is from before the Ferguson merger - a 1952 Massey-Harris 30 - but it is Massey family so I figured it belongs here.

I finished converting it from the original 6V positive ground system to 12V negative ground. The alternator is a GM Delco 10SI 63A from a Chevy Squarebody, single wire and self-exciting, so the electrical side is straightforward once it is mounted.

Mounting was the actual project. Fabricating the bracket and getting everything aligned was by far the most work, and the alternator had to move about 3/4" forward toward the crank pulley before the belt ran right.

Charging results:

- Stock generator pulley, 600 engine RPM: just over 13V. It charges, but I was not comfortable leaving it there.
- Stock generator pulley, idle raised to roughly 650 RPM: 14.4V. That is where it sits now.
- A 2" pulley with a 17mm bore on the 10SI should hit 14.4V at 600 RPM by my calculations, if you can find one.

I chose a voltmeter over the period-correct 60A ammeter that is available. I would rather have the information about battery and wiring condition than the matching look, though I do still want to find a voltmeter that suits the tractor better than the Amazon one in there now. The water temperature and oil pressure gauges got replaced at the same time.

If I did another one I would use the internally resisted ABC6158 coil and drop the external ballast resistor. The 55,000V hot coil has been great regardless - it barely cranks before it lights.

Full writeup with the wiring diagram and the pulley math:

https://forum.fullsizechevy.com/t/1952-massey-harris-30-6v-to-12v-negative-ground-conversion-delco-10si-wiring-diagram-pulley-math/632

This is my own tractor and my own conversion work.

Pre-Ferguson Massey-Harris 30: completed my 6V-to-12V conversion