As I approached the summit of Stevens Pass on US 2 in Washington State, my '59 Corvette started a popping noise from the engine. If I let off, it diminished, power on and it was back. The cam was a 12/18 Duntov solid lifter cam that was common in that motor. Of course it was late at night, but there were no services there anyway, so day or night didn't matter except for the lack of light.
I've had a habit of traveling with at least a basic tool kit for most of my life, so, I removed the valve cover from what I guessed to be the offending side expecting to see a rocker arm that had gone way out of adjustment. What I found was the ball end of the push rod was missing making the push rod too short to open the valve. Of course I didn't have a spare push rod, why on earth would a carry a spare of that?
I began trying to fit a round head machine screw into the shaft of the push rod and after a few the were too big and one that was way too small, I found one that would just slide in and still let oil get passed. I had to add a nut or two to get close to the length of a full size push rod, then put things back together, adjusted the lash, put the valve cover back on and gently drove home.
The next day I bought several pushrods, replaced the broken one and put the rest in my tool box. Never had that problem again.