Doug: That's the most wise method of discovery. The fuse that blew was the blinkers, brake lights, fuel gauge, and temp gauge.

Recently I was messing with my clutch. I removed the arm to fix the spring tab on the top. When I put it back in I couldn't get the clevis in from the back, so I pushed it front to back and put the cotter pin in blind from the back. I drove the car for days like this. Eventually, that cotter pin (longer than necessary and not fully bent over) rotated. It stopped rotating when it hit the brake switch on the subframe then would rock back when the clutch was released. It was barely noticeable until I was desperate for a reason.

I was embarrassed to post this problem because I knew I was missing something simple. Once I found it I hoped you guys would get a kick out of it. Chalk this up to the list of oddities that happen with a 50 year old car. Had I not put the clevis in that direction, had I folded the cotter pin just a bit farther, had I just put the hot wire on the other side of the switch, had I turned the switch in the brake line block 90 degrees more, and on and on.

Pretty sure it starts with a butterfly changing the course of a balloon, but from there I’m lost.

Mark, which fuse blew?  What else was on the circuit?

It was a bad throwout bearing. The frequency of the squeal when the clutch was pushed caused the vent valve on the Lucas smoke canister to release.

I'm thinking that it may be when you depress the clutch pedal and the arm in the engine bay moves and grounds out on something. 

The only thing i know of that is close to the clutch actuating mechanism is the accelerator cable.  Long shot maybe a bad ground that transmitted through the accelerator cable until the clutch was depressed then lost contact and its ground.

Because when you push in the clutch, you also push the brake pedal to stop it rolling and the short is in the brake electircals and not clutch?

Nope. Funny to think about though.

Pantleg catching on a wire?

REALLY big feet?

Recently I was driving home and noticed I blew another fuse. It's been a while, but I also rewired a set of external gauges. I put a new fuse in place and started the car. No problems. Then I pushed the clutch and the fuse blew. That's strange, so I replaced the fuse with a slightly heavier amperage. Maybe the new gauges and lights draw a little more power. New fuse, started the car, pushed the clutch, POP another fuse. Now I'm thinking it isn't coincidence. I know what you are thinking, I just crossed something or wasn't careful. Nope, everything was rewired with new wire, soldered connections and heat shrink over the connections. I checked and rechecked.

I looked under the dash for something interfering with the pedal. One wire was near, but I moved it and it didn't solve the problem.

So here's your mystery challenge: There are no wires even NEAR the clutch pedal or even the slave cylinder. When you start the car and let it run for over a minute, the moment you hit mid clutch stroke the fuse blows. How can a hydraulic system blow a fuse?

I solved it with photos of the problem but I'll let you guess.

No cheating Paul, I texted you in desperation! (and told him how I solved it)