Busy, busy day in the old garage one summer day--we were always slammed just before school started. It'd been like that all week, and we were seeing the light at the end of the tunnel (or is that the beer light in the bar window?). One of our long-time, good customers called and got the chief mechanic on the line. I walked up just as Tony, all sweaty and dirty, said to her "Tell you what, Nadine, I'll listen to the funny noise [your car is making]--put your car on the phone!"
Which, in a way, kindof highlights the difficulty of diagnosing a car on the internet (or on the phone!), and the frustration of the owner trying to follow this, that, and every other suggestion. We feel your pain, Phil. You may end up doing something that I was never all that good at, which is using a volt-ohm meter (in case the primary (power to the coil) and/or the secondary wire (coil wire) is breaking down under load/heat--this is also where the scope check comes in that I talked about.
A really good scope guy (or gal--seen one of two of 'em in my time) can look at the patterns and tell you a lot of stuff, including whether or not you have a potential fuel problem, though probably not a mechanical issue with the fuel system.
Having said all that (again), I'll reiterate this: I'm not very confident that there are that many people out in the repair world who can read a scope that well. Therefore, it gets down to, as some have said here, the basics. It needs fuel, it needs spark, and it needs compression. You have all three, initially, at least, and since only two of the three are going to go away with any immediacy, and then come back, we can safely rule out compression. When compression goes, it goes.
You need a couple of things on hand to begin diagnosing the problem: a continuity light, and a spray can of starter fluid. And maybe a flashlight, if you do this at night. A remote starter switch would be nice, but a helper will do, unless you're fast on your feet.
You need to remove the air cleaner (is it an oil bath, by the way), and go through your normal warm up of the engine.
As soon as it quits running, run around, throw up the hood, and check the following: the choke butterfly. I'm assuming it's a manual choke, but that doesn't mean it doesn't work its way closed, choking the life out of your engine.
If the choke isn't slammed shut, shake your starter fluid a couple times, and squirt a couple of quick squirts into the venturi of the carb. Try to start the beast. If it doesn't fire until the normal cool-down period has passed, the problem is almost certainly electrical. If it does try to go varoom! you're looking at a fuel delivery probem.
If it's electrical, never my strong suit, and you have at least a strong, orange, but optimally blue spark, and the spark goes away, the problem could be a broken power wire on either side of the coil. Remember, you need at least 9.6 volts for the thing to work (it is 12 volt system, right?). Some cars and trucks got their coil primary power from the starter; grease, oil, small furry animals, ham-handed mechanics, debris, could break a wire to where it works, but then doesn't work (heat, vibration, stuff).
It could be the primary wire from the distributor to the coil...the one that the points interrupt to induce the coil to spark. It's possible that the coil secondary (the thick one that goes to the center of the distributor cap) is broken, and heat causes a gap too great to bridge. This is where the ohm meter comes in.
Other possibilities include the distributor cap itself (cracks), the rotor bug (holes burned), though you usually see these with HEI more than with points. The coil itself is a major suspect, especially if the spark is less than optimal (blue). The points themselves, and the ground wire in the distributor should not be ruled out.
None of this stuff is long-haired thinking type stuff--just takes time and patience. That's enough for now. We can get to the fuel delivery stuff (most of which has been covered already) if the problem seems to you to be fuel-related.
