850 lurching at high rpm/ and gear

It sputters and lurches at high rpm and in highest gears at almost full throttle.

Low idle and low gear it runs great.

I ran her hot for about an hour. Shut her off and let her sit for 40 minutes. Went outside to restart her and she wouldn't cath fire. Plumes of grey exhaust sputtering out of the exhaust, but would not fire up.

Let her sit til cool another half hour, cranked on her and she fired up after some sputters and weak false starts, then finally she started...turned distributor cap about 1/8" to get her to really even out and purr.

WHat's the problem you think given that she sputteres at high RPMs in high gear and I then have to monkey with the choke to keep her from sputtering and stalling out...and won't start when hot (now)?

Hel;p please my chores are stacking up and I would really like to get through this problem before my woman starts on my case.
bob

1) It takes more spark voltage to fire the plugs at higher pressure (more throttle) than low pressure. A weak coil would have trouble running the engine at high load and might also be temperture sensitive. Bad insulation on the coil secondary wire could also do this, but probably wouldn't be temp sensitive. Plug wires would all have to have the same problem or you'd be able to tell that it's not running on all cylinders, so I doubt that's it.
The reason this doesn't fit completely is because it sounds like at low RPM and high load, things are OK.

Just some general thoughts.

1) I'm assuming the governor keeps cycling from part / low throttle to full throttle when it's lurching?
2) If so, it sounds like it's running lean at high RPM and requiring the extra fuel from the accelerator pump to run (I assume your carb has one?). That would also explain the need for some choke.
In this case, I'd assume it's a partial clog somewhere in your carb main metering system. I'd open it up and clean it if you haven't already.

3) All that assumes the timing is correct, of course. So I'd also check check the timing advance mechanism (you'll need a timing light and timing specs at other than idle). Could be sticking centrifugal weights in the distributor or maybe a sticking vaccuum advance (If you have that).

4) I'd rule out a vaccuum leak for now, that would cause more trouble at low throttle.

5) There's always the chance that a valve is misbehaving, but you'd probably hear abnormal ticking in that case.