Bizarre '73 280C Problem
 

Will also post this on the Vintage board.

So the big moment arrives. Senior Management and I are going for a ride in the 280C with its rebuilt engine with about 5 miles on it. The plan is to take Route 50 east to DC, then back to Falls Church via the GW Parkway and some back roads. Some quality miles on the new engine. Nice day for it, but a bit cool.

About 15 minutes out, the engine dies. No noise, nothing unusual, it just stops while cruising at 50 mph. Oil pressure pegged. Water temp a bit cool. Coast to a stop. Engine will not turn, despite lights, horn and a good solid thunk from the starter. Despair builds. Have car trucked home.

No clues. Lots of battery (12.75V), oil OK, coolant OK, no loose wires. Timing chain looks good. But acting like a seized engine. I despair and begin organizing tools for investigation. Out of curiosity, give key a try, and starter turns slowly and engine fires. Try it again, and engine starts and runs. Go around block like nothing ever happened.

Any ideas? TIA.

Fouled ignition points. Those cars used mechanically triggered transistor ignition and had almost no current flowing through the points. They insulate with the slightest smudge.

I have had brand new points out of the box leave me on the side of the road more than once. Drag a dollar bill through them and then grind them together (be sure they are closed first of course).