I know that the gurus above have a lot of experience with 216 motors. I don't. I do know about motors in general. But answers can't begin without asking some questions.
1. What do you mean? You want to "improve warm starting", what does it do or not do?
2. Does it barely turn over/too slow to start a motor? Does it turn over quite a bit slower when hot or about the same? If it's way slower it's not a fuel problem.
3. Does it puff and die?
4. Does it run down the battery?
5. Does it do it after 10 minutes or an hours drive?
6. How long does it take to "cool" and act normal? What is normal?
7. How fast does it start in the morning?
8. How long does it crank before starting when "hot".
9. Do you know how hot it gets? Gauge? Would a better radiator help?
10. How many rebuilds in 46 years and who did them? Any rewiring? Starter swap outs? Carb rebuilds?
There are a bunch of reasons for this problem.
Here are some:
1. Electrical cable size as said. Maybe some folks buy a 12V size cable for a 6V system or a aftermarket harness may not be sized for 6V. Not sure. Anyway the heat creates a voltage drop in wires/cables/switches/coils/ignition parts/THE STARTER. Too much resistance, so proper wires and components are required. Shielding the starter may help A LOT. Don't know that grounds break down with heat. I don't think a tight mechanical ground will cause problems when hot.
2. Heat soak in carb or lines.
3. Some moving parts can get tighter inside motor.
4. The battery can get hot and evap fluid and break down. I assume you have had this issue with old and new batteries.
5. The issue can be fuel, electrical, mechanical or all. This takes testing. Like: voltage drop testing hot vs cold. Battery testing hot vs cold.
6. I would have gone to 12V a long time ago. Like 46 years ago. It strikes me that if it really has done this for 46 years it will take another motor of a different era to correct. Don't know if this is a truck or a car but it was designed to start when "hot", even in freezing cold Canada. If all the wires and cables are at least original size, and they are not adequate, then all 1946 trucks have this problem? Especially in boiling hot Arizona?
7. It would be beneficial to know the actions of the motor and answers to the above questions...... and any other info/clues you can think of.
8. CarbKing speaks of modern fuel volatility but you say done this for 46 years.
"HARD STARTING, HOT
Difficult starting of a hot vehicle from 5 minutes to an hour after the engine has been operated, can be caused by the volatility of modern fuel. If you have this problem; try using the following method to start the engine: DON�T touch the footfeed (VERY important). Crank the engine over from three to 5 seconds (different vehicles will respond to different times); and then GENTLY (so as not to activate the accelerator pump) press the footfeed approximately 1/3 of its travel. The engine should start, and may run rough. Run the engine at a high idle for about 10 seconds. This issue is caused by volatility of modern fuel. Once the engine has been shut off, the gasoline is heated by the latent heat of the engine, and percolates the fuel from the bowl into the throttle area, forming a mixture that is too rich to fire. If you push the footfeed to the floor (as has been the traditional method of �unloading� a flooded engine) the gasoline continues to flow into the engine (again due to the volatility). By not touching the footfeed, you do not open the throttle plates, and the engine will pump the overrich mixture out of the tailpipe. Once the overrich mixture has been alleviated, gently opening the throttle will allow the engine to start" (CarbKing)
Many motors will start after hot with pedal gently put to floor and held there until it starts. I suppose you have tried all this in 46 years.
Papas52 has also given a third thing to try.
There are lots of other "no start" issues like build up of vacuum in tank but those don't apply to "doing it for 46 years" because parts have been changed many times usually....... and also don't apply to cold good/hot bad.
