6 volt ignition switch question

[c10 custom]

Hi guys i have a 1947 gmc truck second series looks like a 48
anyways i was wondering can i leave the original ignition switch when
changing to 12 volt system i am going to install a distributor from a 1981 chev truck with HEI 6 cylinder engine any advice would be great thank you everybody

[OrrieG]

I think the ing switch will be ok, but go over to the stovebolts.com tech section and look at the electrical 12v conversion thread. It tells in detail what will and will not be affected.

[_Ogre]

like orrieg mention the switch will work, you have less amperage on 12v vs 6v for a given load
you will need to add a push button for the starter if you choose to keep your old switch
not sure if your switch has an acc position either.

[mr48chev]

As Ogre said you will need to add a push button for the starter but the switch will handle the ignition ok if it is in good shape.

If you are worried about the switch handling the draw from the HEI install a relay for the HEI that is activated by the ignition switch. That would solve the load problem and be a real easy hookup.

[c10 custom]

how is the relay wiring supposed to look hooked up do you have a wiring diagram for this

[OrrieG]

On a boush type relay 12v power goes to pin 30. pin 86 grounds. pin 87 goes to HEI power. pin 85 come from ignition "on" wire that would normally go to the coil or resistor. So when you turn the key to ON it closed the relay connection allowing full power to flow from pin 30 thru the relay out pin 87 to the HEI. Mount the relay as close to the HEI as possible on the firewall side.

HEIs need full 12v power not shared with anything else. If it comes directly from the battery or alt connection use a 12 GA wire with 16GA fusible link. The ing switch to relay wire can be 16 GA.

[Zach B]

Actually on my grandfathers 55 first he converted it to a 12 volt system and changed the switch. However he left the starter as a 6 volt. The truck actually starts a little faster this way. You have to be carful though because it's easy to burn up a starter.