42 chevrolet truck

hello, fire department has a 42 chevrolet straight 6 parade truck vehicle. this truck will run all day when cold, and start great when cold, but is very hard to start when warm. sometimes it seems like the " Generator" is not charging, this is still 6volts, anyone know where i can find something like this. and any ideas or suggestions?

6 volt systems were notorious for hard starting and slow cranking especially with 6 and 8 cyl's......this is why everyone went to 12 volt back in the mid-50's. Heat only makes the situation worse......the electrical resistance in the starter motor and battery cables goes up when they are warm from engine heat.

A VERY common error is to use 12 volt battery cables on a 6 volt system.
6 volts simply needs THICK battery cables for lower electrical resistance. If you have never seen 6 volt cables, you would be amazed at their size. They have a copper core just about as fat as your thumb. However, this cable has not been available for decades in cars, so 12 volt cables are used intstead.
You can try doubling up the existing cables, or try a farm tractor or welding supply store for the thick 6 volt wires.