Is the short battery-to-relay cable getting hot, or is it the relay-to-starter cable? OR both?
A hot cable is being overworked at some level. The reasons can be multiple.
1. Cable too small for the job.
2. Related to that, a cable with broken or corroded strands or rusted ends can't pass the current efficiently and heats up. Same as the cable being too small.
3. The load is too large for the cable (same result as being too small, but not the cable's fault this time) from the starter getting old and tired, OR the engine being hard to turn over.
4. Related to all of the above, insufficient connections at either end of the cables.
5. And I suppose related to the above as well, if a cable is too long. Same as being too small a gauge, but coming at the problem from a different angle.
6. Excess heat getting into the cable from an external source. More heat equals more resistance, which equals more heat. Literally a downward spiral, sometimes to the death of the wire.

If it was the short battery cable that was heating up, it's likely that the load is just too large from the starter or engine being locked up. They are usually so short that you can almost get away with 8ga, but they never go that small because it's just not worth the gamble it might be called upon to do extra work someday.
The 6ga that typically came from the factory was just enough when everything was new and working well. I consider 4ga to be the bare minimum, and personally always go to 2ga or larger (some of my trucks use 1/0 and 2/0 welding cable) when I can. And as a general practice I always keep them as short as possible while still routing them out of the way of heat.

So if yours are of sufficient gauge for the normal job and are getting hot, there is too much load from somewhere, or a bad connection.

Good luck. Check all cables and connections, but I'm curious how the testing goes to see how hard it is to turn over the engine by hand. I wonder if something in the transmission got jammed up.

Paul

 

the hot wire is the battery to solenoid. It is currently 4ga.

I was able to turn the motor a little using a ratchet. But then it got very hard. My FIL said that I reached compression and now I can’t move it any further.

I won’t be able to touch it again until December. I’m going to try to remove the spark plugs to see if I can get it to move some.

im suspecting this has something to do with the misaligned NSS and it started in reverse.

 

When you get the plugs out, put a few ounces of marvel mystery oil in each cylinder, let sit 30 min. or so. You'd be surprised at how much easier it'll turn.

 

The neutral safety switch just interrupts the wire that goes to the i terminal on your solenoid. If you bypass the solenoid (like you did with the channel locks and it didn't make noise, then you are missing a ground. Starting it in reverse shouldn't damage it as it wont even turn the transmission until the rpm gets up enough to get the torque convertor to engage. Your battery should be grounded to your engine block. Check that. It could also be a really bad battery cable that gets corroded inside the wire casing. I've seen that in boats. Use jumper cables to run from the negative to the engine block or a starter bolt.

 

Definitely take the plugs out and try it, but I've never run into a normal engine that you could not turn over by hand even on the compression strokes. You can feel it tighten up of course, but you can always turn right through it. At this speed (or lack thereof) there is always leakage past the rings at the very least.

Paul