Looking at the wiring diagram on my 68's it shows a #14 wire going from the battery to the junction block and a #10 wire going from the junction block to the alternator. Why the different sizes? What happens if I run a #10 wire all the from the alternator to the battery? I just don't see a need for the junction block other than to link together two different size wires. Does the #14 wire going to the battery cutdown the amount of amps/volts returning to charge the battery?

Looking at the wiring diagram on my 68's it shows a #14 wire going from the battery to the junction block and a #10 wire going from the junction block to the alternator. Why the different sizes? What happens if I run a #10 wire all the from the alternator to the battery? I just don't see a need for the junction block other than to link together two different size wires. Does the #14 wire going to the battery cutdown the amount of amps/volts returning to charge the battery?

The #14 wire is designed to protect the rest of the wiring from an overcurrent condition by being the first piece of wire to burn. During normal operation it has very little effect since #14 wire has a resistance of .00258 Ω/ft. If you were conducting 50 amps through it the voltage drop across it would be .128 v/ft, a measurable but not real significant drop.

Looking at the wiring diagram on my 68's it shows a #14 wire going from the battery to the junction block and a #10 wire going from the junction block to the alternator. Why the different sizes? What happens if I run a #10 wire all the from the alternator to the battery? I just don't see a need for the junction block other than to link together two different size wires. Does the #14 wire going to the battery cutdown the amount of amps/volts returning to charge the battery?
The 14g wire is a fusible link and should be fusible link wire, not just regular wire. Like onovakind67 said it protects the rest of the cars wiring from the battery incase of a major short, it would burn in two first before damaging the rest of the wiring. When the car is running, the alternator powers all accessories and charges the battery. With a fully charged battery only a amp or two flows through this wire.

http://www.chevelles.com/showroom/data/500/medium/Original_Chevy_system.jpg

I am the original owner of the car. It and my other four 68 Chevelles don't and never did have a fusible link. The 1968 wiring diagram does not show a fusible link. However, I think it should probably have one. Still looking for more input. I trully appreciate anyone who chimes in with your thoughts.

Still looking for more input.

What kind of input are you looking for?

When I say "input" I mean reasoning of why the wire size is different. I should say I was born in Missouri (the show me state), so I need more proof of the ideas that are being submitted. Just not totally convinced. It things like that make me go hmmm... Really appreciate the input.

There's only one reason for the smaller wire and that's to protect the downstream wiring. When you choose wire to do this, you select a wire that's 4 sizes smaller (numerically larger) than the wire you are protecting. In this case it's the 10 gauge wire that goes from the junction block to the horn relay and the downstream wiring, including the wire back to the alternator. If you happen to short out the horn relay or the alternator it won't burn up all the wiring coming across the front of your car, just the short piece of 14 gauge wire that goes to the junction block.

I am the original owner of the car. It and my other four 68 Chevelles don't and never did have a fusible link. The 1968 wiring diagram does not show a fusible link. However, I think it should probably have one. Still looking for more input. I trully appreciate anyone who chimes in with your thoughts.

Directly from the Chassis Service Manual, page12-2, 12-3--
"Engine compartment wiring harnesses incorporate several fusible links. The same size wire with special hypalon insulation must be used when replacing a fusible link.
The links are:
1. The pigtail lead at the battery positive cable (except Corvette) is a 14 gauge, brown fusible link protecting the 10 gauge battery charging circuit. This wire is an integral part of the battery cable assembly and servicing requires replacing the complete battery cable assembly."

The manual goes on to tell about the 16 ga black link at the horn relay, a 20 ga orange link on the battery feed to voltage regulator #3 terminal, and 2 20 ga orange wires protecting the ammeter circuit.

Hope that "showed" you enough there.:)

BillL

As Greg mentioned earlier it's not just a standard 14g wire, it may look like one but it is not. Go to the auto parts store and ask for fusible links. Looks just like standard wire, 12 to 18 inch long usually. The insulation is designed not to melt and burn when the wire inside melts. A fusible link is always 2 sizes smaller than the wire it's designed to protect. In this case 14g to protect 10g.