Wiring for Alternator, HEI, Lights, Fuel Pump

[bhap]

I'm trying to keep this simple, but sometimes I think I think too much. I have a 62 C10 that has an L31 crate engine going in with HEI and an electric choke Quadrajet. The alternator is a CS130 100 amp. Using a GM HEI, Carter P4070 fuel pump and also installing a Saginaw 3 speed overdrive. My plan is to only upgrade the wiring under the hood and keep most of the new relays and fuses where the voltage regulator used to be. I'll attach a rough sketch of what I think will work, but would appreciate any suggestions for improvement or safety. I'm thinking of using a Bussmann 37702 power relay module to get a switched 12v source and large fuse protection coming off the alternator. One side of the Bussmann is switched and the other is constant 12v, both have a fuse - each side is max 70 amp. I'd like to use the input stud on the Bussmann as a junction block to supply the battery and also the original fuse box (with the supply wire upgraded to 10 gauge with a 14 ga fusible link). Battery charge wire would be 8 gauge with 12 gauge fusible link. The two outputs from the power relay module would feed two small fuse blocks that would supply headlight relays, horn relay, fuel pump, electric choke, HEI relay and overdrive relay. I think I'm ok going direct to fuel pump without a relay (but through an oil pressure switch) and also direct to the electric choke. Can I combine the fuel pump and electric choke wires on one circuit and run both through the oil pressure switch? I've seen where people say yes, but also that if choke fails and blows a fuse, it kills the fuel pump too. The setup with the overdrive kickdown switch requires an HEI relay or I'd wire that direct to the switched 12v too. Thanks for reading and for any help laying this out.

Bob

[dmjlambert]

I have a couple thoughts on this:

• A fusible link protects the smallest gauge wire in your circuit by fusible link burning up first if you have a short. If the 10 gauge wire that goes through the firewall to the fuse box also connects with non-fused wiring such as 12 gauge wires to the ignition switch, headlight switch and stuff like that you may want to use a 16 gauge fusible link on that 10 gauge wire.
• It looks like you've thought of making sure your fuel pump doesn't continue to pump after a collision and spew gas, using an oil pressure switch sounds good. I have also seen in catalogs fuel pump control modules that work using the tach signal from the distributor. I recommend all metal hard fuel line on the pressure side of the fuel pump going to the carburetor.
• I have heard of using an oil pressure switch to power the electric choke so the warm up of the electric choke coil only starts when then engine actually starts. It seems like a good idea to me and I don't think it is likely an electric choke would blow a fuse. They don't draw much current.

[lutronjim]

I had an overdrive that I put in my 70 C10. In my points type dizzy there was a wire from the dizzy side of the coil that stopped the engine momentarily for the overdrive to shift.

When I upgraded to a HEI a mechanic friend help me wire it up. He simply put the wire on the tach terminal and it worked fine. I don't know why but I ran that way for several years. I didn't have a tach so I don't know how that would work. As I remember he said it just stops the engine for a partial revolution.

[cwcarpenter98]

I'm running an HEI in my 63 with a Muncie 3 speed overdrive.
For the HEI, I removed the cloth covered resistor wire that goes from the firewall down to the starter and then back up to the coil. In its place, I ran a regular wire straight to the power plug on the HEI. That way I didn't have to add an extra relay or anything to power the HEI.

For the overdrive wiring, I used an additional relay to make the overdrive turn off the HEI ignition module just like turning the key off rather than grounding out the module like how the normal wiring grounded out the coil. That wiring is described in the link in my signature.

I'm no help on the alternator though because I still have the factory one in there

[bhap]

On the HEI, I think the idea is to use a relay to interrupt the Positive feed to the HEI instead of grounding the tachometer. On points ignitions, it's ok to ground the coil to kill engine momentarily so overdrive can disengage for the "kick-down".

Christian, do you know if the resistor wire is only on the engine side of the firewall connector? I'm thinking of installing a regular wire on the engine side to trigger my HEI relay.

On the fusible link, that is a good idea to use a 16 gauge since the wires on the inside of the connector are most likely 12 gauge.

Thanks for the help, I'm going to get started wiring this up.

[cwcarpenter98]

Originally Posted by bhap

On the HEI, I think the idea is to use a relay to interrupt the Positive feed to the HEI instead of grounding the tachometer. On points ignitions, it's ok to ground the coil to kill engine momentarily so overdrive can disengage for the "kick-down". That's a much simpler way of saying what I was trying to say above. Yes, that is the idea.

Christian, do you know if the resistor wire is only on the engine side of the firewall connector? I'm thinking of installing a regular wire on the engine side to trigger my HEI relay. On my truck, yes, that was the case. I pried the connector off the resistor wire and reattached the connector to a new wire that I ran directly to the power terminal of the HEI. I did the HEI before I found the overdrive. I didn't have a proper HEI power and tach plug, so I just used an insulated crimp terminal. It worked well to swap over to the HEI relay when I added that in.

My responses in green