MGB: smoke in Cabin

Today while driving home from work, I was a block away from home and smoke, bitter smelling, started floating into the cabin,
Off with the engine, I coasted into my driveway and popped the hood, no smoke, no smell.
I cranked her up again and put her in first and on up into the driveway, and it started again.
It was streaming in from under the dash, but I couldn't figure out from where exactly.
Five minutes later I cranked her up and no smoke.

Is it possible that its coming from the radio, It wasn't on the third time. But just ran her a little more in gear and no smoke returned. Should I take everything apart and try to dig out the culprit or just drive her until it comes back? I don't think I have any oil leaks and it's not in the engine bay? thoughts?

did it smell like wiring insulation

better look for the fried wire ,, it might be important or result in a true enough cabin fire..
not good

Sounds like an electrical short to me. It probably shorted out, burned up a wire and only stopped smoking when the wire melted apart. Personally, I would try to figure it out before I drove it again.

Yes, do be careful John. I too would suspect a shorted wire. Take a systematic approach to tracking it down. Do a visual inspection first. Look under and behind the dash with a mirror and flashlight. Look behind the radio console as well. If everything is in order, take another step. With the battery ready to disconnect, carefully test systems and see if something is not working. If you discover an inoperative system, disconnect the battery and inspect further.

Pete

Check the fuses. If one blew, that would narrow down what group of circuits may contain the short. (and would explain the end of the smoke)

You obviously need this:

Often you can feel one or more hot wires when there is a short. I'm not going to recommend starting the car again, but if you do then feel all the wires for excessive heat.

Thanks David...I'm glad Lucas still carries that stuff, I'm not used to needing fresh smoke.

I think it may have been heater related. I'll find out for sure when I have some time tomorrow. But I've got a plan of attack now. I'm thinking it might also be radio related, I moved a lot of the wiring around back there and probably cracked two wires against each other for the smoke to get out.

Declared an emergency in a jet once with that. We found a runway and quick! Prefer to be on the ground when that happens.

You might check the wires under the dash that are near the two heater control knobs. The knob rack is a usual suspect for chewing up a wire that just happens to droop or dangle too close to the racks that the knobs turn to move the control cables. Don't ask how I know this.

Just because the smoke stopped, don't think the problem is gone because all the magic smoke leaked out. It just means the insulation on the circuit that was hot is melted off - the last thing you need is an auxillary heater - the problem is still there. There is high resistence (or short to ground) somewhere. Find the crispy wire and trace it to the source.

Turns out PO had wanted to replace the wiring harness to the ignition switch, but instead spliced the old one to the new and an connected it to the system. Seems the guilty wire was to small for the juice and just melted. the original wire is 10 gauge but the new harness had only 16. I just replaced it with some proper 10 gauge and she works great. Pretty easy fix really and it shouldn't melt again with 10 gauge instead of 16.