This has me stumped and any help is greatly appreciated. Gas engine 464. It runs great in all ways. Couple months ago it developed this problem of quitting heading uphill. Runs great downhill and level. Have cleaned the entire fuel system, to the extent possible. Fuel flow to the carb is good. Cleaned the carb multiple times. Polished the needle valve, blew everything out. It will start and run fine for a little while and then start quitting again. I raised the float level a bit, inspected everything and can find no issues. The fuel solenoid that prevents dieseling has been removed for years. Suggestions?