Recently put a 302 in a 56 f100 , want to use the original gauges , when we hook up the amp gauge and start the truck it sends the needle right to full charge . I believe it has a 40 amp alt. Is the gauge not rated to handle the higher amperage ?? I Water temp gauge also doesn't want to work either it is an electrical gauge . I suspect it has a non comparable sender in the 302 ??
Use a temp sender for the truck, not the motor. It doesn't care what motor it is in, just what gauge it sends its resistance to. Was the truck 6 volt and is now 12? Was positive ground now negative? The ameter was rated for a lower amp generator, not an alternator. I know... amps is amps, but I am betting the alternator output is quite a bit higher than the generator would have been. Measure the amps.... that will tell the tale.
Graybeard is correct. When I put the 460 in my 56 I used the stock temp sender from the Y block. Worked great. Same with the amp gauge, I think it’s only rated to 30 amps. We ended up not hooking up the amp gauge. My father came up with idiot lights from some other Ford that bolted in the stock gauge holes and we used those for the amp and oil. I can’t remember what they came off of but the font of the lettering was exactly like the F100 and looked like it was factory.
On later 60’s Ford pickups they are not a true amp gauge, if you google you’ll find the proper wiring schematic, I expect 56 may be the same way.
The 1956 Ford Pick up is a 12 volt, negative ground . It has been years since I looked behind the dash of one. Is it possible you could show us a picture of the back of your 1956 Ford pick up amp gauge and associated wiring? . Or at least describe it? Bones
If it was a V8 then I think they had 2 sending units like a Flathead (please correct me if I'm wrong). If so you need to use the single wire sending unit and fine tune with resistors or a shunt as needed.
If you have the magnetic amp gauge where the wire passes through a loop on the back of the gauge, you can run 2 wires, one through the loop and one outside the loop. It will cut the current in half that the gauge sees, but it will still tell you if the alternator is charging.