Purchased a 1969 C10 Short Bed - Pleasanton, CA

[Luke87gt]

Tonight I put the kids to sleep, grabbed a beer, and replaced the valve cover gasket on the 250. I also gave the valve cover a degreasing before I bolted it back up.

The rockers look sludgy, let’s see if this 250 will come back to life.

[Luke87gt]

Also, I haven’t had a chance to trace these wires yet but wondering if you guys may know where each is going…

To clarify, there is a wire coming from the battery’s + lead into the pictured bank. Then there’s 3 additional wires coming off of that hot bank. Thanks

By the way, one thing I am not used to at all is how difficult it is to reach the back of the motor on these C10 trucks lol. For example, getting to those back valve cover bolts should qualify me for the next Olympic gymnastics trials

[SRU1436]

Originally Posted by Luke87gt

Also, I haven’t had a chance to trace these wires yet but wondering if you guys may know where each is going…

To clarify, there is a wire coming from the battery’s + lead into the pictured bank. Then there’s 3 additional wires coming off of that hot bank. Thanks

By the way, one thing I am not used to at all is how difficult it is to reach the back of the motor on these C10 trucks lol. For example, getting to those back valve cover bolts should qualify me for the next Olympic gymnastics trials

Attached is the wiring diagram for the truck. You’re talking about the junction block. I am not sure if the straight 6 has an additional wire. This will help you get started. If you trace them it will help you figure where they go.

The engine bays on these trucks are large, sometimes I use a small step ladder to reach the back.

[Luke87gt]

Thank you for that!

It looks like one of the wires runs to the fuse box. The other is labeled “Engine Ham” … what is that?

And then I need to trace the 3rd mystery wire on my 6cyl

[MikeB]

It's quite common to see other stuff wired to the junction block. But from the factory the junction block has a 12 gauge wire coming from the battery, and a second wire going through a 16 gauge fusible link, and then on to the "splice" on the drivers side of the radiator support. At the soldered splice, the battery wire is connected to the alternator output wire and the fuse panel feed wire.

It's been a while, but the mechanical regulator may also be connected to the splice.

If your truck has an ammeter instead of a warning lamp, the wire that runs from the battery junction block to the splice will actually be a resistance wire with tiny fuses on each end. The ammeter is actually just a voltmeter with "zero" in the center, and it responds to current flow and direction (charge/discharge) across the resistance wire. Kind of a strange way to do it, but I guess GM didn't want to run 30-40 amps into the cabin and use an actual ammeter.

[Steeveedee]

^ GM was smart to use a shunt, in my book. I've been under the dash of many a Mopar with scorched wires at the ammeter. Thermal expansion and contraction eventually created a weak connection.

[MikeB]

Speaking of resistance wire: On some GM cars, instead of a ballast resistor on the firewall, the wire from ignition switch to coil is a resistance wire, and it was bundled in with other wires under the dash.

I worked on a 64 GTO that was hard to start, and wouldn't rev like it should. Turns out someone had added an HEI but left the resistance wire in place, so the distributor was getting only around 9 volts. That resistance wire was melted into an under-dash wire bundle, so I replaced it with a 12ga wire. After that, the engine started easy and revved well. But I had aches and pains from lying on my back!