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Untangled- Wiring a Classic Corvette

Wiring Lead

Rats nest, spaghetti, copper conjunctivitis; call it what you want, but wiring is the single most feared aspect of all automotive projects. Whether you are chasing gremlins through a 50-year old survivor, or re-wiring your muscle car, most gearheads just don’t enjoy wiring. It doesn’t have to be this way, though, there are tricks and tips that can turn a nightmare into a job well done. And you don’t have to have a degree in electrical engineering either.

There are two main types of wiring projects: fixing an existing system, or replacing it. When you are dealing with 40+ year old wires, often the best solution is total replacement, especially if you have the car apart already. That is where we are going to start; a total rewire on a 1967 Corvette. This car came into the shop, as many do, fully disassembled; one man’s failed build sold off to another. While we had the original harness, most of the terminals were broken, the wires cracked and corroded. It simply was not worth trying to fix, especially considering the car was being fully rebuilt. Starting with a clean slate is always nice. We made a call to Painless Performance and they sent us the harness we needed.

We could have ordered a factory replacement harness, which is pre-terminated and bundled just like the factory harness; everything is where it should be for the stock components, but that would not work for our project because we had installed an LS1, electronic transmission, aftermarket gauges, and all the new-fangled goodies you would find on a new car. We needed to plan out new routing for this complicated wiring system. To do that, we ordered a 12-circuit universal harness, LS1 engine harness, and a really cool system called Phantom Key. The Phantom Key is a transponder-based push-to-start module that eliminates the need for a key. Just hit the button to unlock the doors, get in and hit the button to start, just like the newest cars coming out of Detroit. This provides the ultimate in regards to the cool factor.

To get started wiring, you need some tools. It is important that you use quality tools for this, because some cheap versions can cause more problems down the road. The most important tool you will use in a wiring job is the crimpers. Crimp connections often get a bad reputation because of poor installation. A properly made crimp is just as good as a solder joint. The key is correctly sized terminals and quality crimpers. Those cheap combo crimp-n-strip tools are not any good, throw them away. They are only good for emergency repairs. You need a set of good crimpers designed for insulated terminals. Klein and KD tools make excellent crimpers.

Wire size to terminal selection is critical. Using too large of a terminal will result in a weak connection. Most terminals are color coded for size. Red is the smallest, fitting 22-18 gauge wire, blue for 16-14 gauge and yellow for 12-10 gauge wires. Anything bigger is sold by the size, not color. Primary wire, is typically an 18 gauge wire, this is the most common wire you will find in a wiring harness. The larger wires that feed heavy-draw circuits are typically 14-12 gauge wire. The wire in our Painless kit runs a little larger than the standard; the primary wires are 16 gauge, with 12 gauge for heavy draw items such as the headlights.

Once you open the box, and see several thousand feet of wire, it can be scary. Fear not, it is not that bad, just be patient. The first step is to take it all out of the box and lay it out on the bench or floor. Separate all the bundles. The Painless kits come pre-bundled in all the major groups: engine, dash, and tail. From there, they are broken down into subcategories. These are good for the typical project, but you may find a few wires that need to be moved to a different section. Now is the time to reroute any wires. Once you are in the car, this becomes much more difficult. Go over each wire and its location and check the car. For example: if you are installing an electric fuel pump under the hood, then you need to alter that wire’s routing, because it would normally be found in the tail section.

All Painless wiring kits provide only the power side of the circuit, save for a couple of situations, you must provide all of the ground connections. While this is typically a simple thing, Corvettes require some additional forethought, because fiberglass does not a good ground make. Painless Performance thought ahead on this one. They offer a ground kit that comes with wire and several terminal strips to provide multiple ground circuits where you need them.

Wiring an entire car requires planning, time, and lots of patience. If you find yourself getting frustrated with a particular section, get up and walk away for a minute. Without juice, it isn’t going anywhere. A novice builder should be able to complete a basic wire harness replacement in 3-4 days. The more circuits you have and the more complications you add, such as EFI, audio systems, etc, the longer it will take. If you take your time and plan out the locations of all of the wires before you cut anything, your wiring project will look and function great.

1. Each Painless Performance kit comes with all the basics: terminal pack, relays, and zip ties. You will often need more terminals than what is included, so make sure you have plenty of assorted terminals on hand. You can order bulk terminals direct from Painless.

1. Each Painless Performance kit comes with all the basics: terminal pack, relays, and zip ties. You will often need more terminals than what is included, so make sure you have plenty of assorted terminals on hand. You can order bulk terminals direct from Painless.

 

2. The first step is to break down the harness and split up the groups of wires. Plan out the layout of the harness before you get to the car.

2. The first step is to break down the harness and split up the groups of wires. Plan out the layout of the harness before you get to the car.

 

3. You need to know how to properly install wire terminals. We use a speed stripper, which really hurries up the process. This pair is 14 years old, they really work great. A standard wire stripper works just fine too.

3. You need to know how to properly install wire terminals. We use a speed stripper, which really hurries up the process. This pair is 14 years old, they really work great. A standard wire stripper works just fine too.

 

4. The key to a good crimp is quality crimpers. This pair works great for insulated terminals, the kind we are using on this car. They will also work for non-insulated terminals as well.

4. The key to a good crimp is quality crimpers. This pair works great for insulated terminals, the kind we are using on this car. They will also work for non-insulated terminals as well.

 

5. Select the correct size of terminal for the wire and insert it into the corresponding set of jaws in the tool. Using the wrong jaws can result in over-crimping (which breaks the terminal) or under-crimping (which results in a loose connection).

5. Select the correct size of terminal for the wire and insert it into the corresponding set of jaws in the tool. Using the wrong jaws can result in over-crimping (which breaks the terminal) or under-crimping (which results in a loose connection).

 

6. A properly applied crimp should look like this. The insulation is slightly bulged, but not squished. You should always tug on the wire and terminal to ensure it is not loose.

6. A properly applied crimp should look like this. The insulation is slightly bulged, but not squished. You should always tug on the wire and terminal to ensure it is not loose.

 

7. Next, you need to locate where the engine side of the harness will go through the firewall. On the Corvette, we used the stock location. You have to be careful because sometimes the hole you choose has another function.

7. Next, you need to locate where the engine side of the harness will go through the firewall. On the Corvette, we used the stock location. You have to be careful because sometimes the hole you choose has another function.

 

8. The fuse box mounts to the firewall with 2 bolts. It can be a real pain to install the fuse box, having a friend help will alleviate a lot of frustration here.

8. The fuse box mounts to the firewall with 2 bolts. It can be a real pain to install the fuse box, having a friend help will alleviate a lot of frustration here.

 

9. The kit comes with a metal backup plate. We trimmed ours to match up with the firewall.

9. The kit comes with a metal backup plate. We trimmed ours to match up with the firewall.

 

10. Inside the car, we separated the bundles of wire into groups and began routing them to their locations. Don’t cut any wire until you have it fully routed.

10. Inside the car, we separated the bundles of wire into groups and began routing them to their locations. Don’t cut any wire until you have it fully routed.

 

11. The neutral safety switch and backup light wires were routed to the shifter and terminated with spade terminals. This makes removing the shifter a no-cut proposition. You may not need to remove it, but if you do, this makes it better.

11. The neutral safety switch and backup light wires were routed to the shifter and terminated with spade terminals. This makes removing the shifter a no-cut proposition. You may not need to remove it, but if you do, this makes it better.

 

12. We are using Painless’s Phantom Key push-to-start system, which includes keyless entry. This system replaces the ignition key with a push button and includes all the relays. We mounted this under the center console in the Corvette.

12. We are using Painless’s Phantom Key push-to-start system, which includes keyless entry. This system replaces the ignition key with a push button and includes all the relays. We mounted this under the center console in the Corvette.

 

13. The main ignition wires are all 12-gauge wire. These feed the majority of the electrical system.

13. The main ignition wires are all 12-gauge wire. These feed the majority of the electrical system.

 

14. There are two main power feed wires, which are terminated to the large feed wire that connects to the battery. This was terminated with a single large 12-gauge wire terminal. The 2 wires on one side are smaller than the main feed wire.

14. There are two main power feed wires, which are terminated to the large feed wire that connects to the battery. This was terminated with a single large 12-gauge wire terminal. The 2 wires on one side are smaller than the main feed wire.

 

15. Most Painless kits do not come with any ground circuits. Usually this is not an issue, but with Corvettes, locating a good ground can be a bear. We made a ground harness for the rear taillights using ring terminals and 14-gauge primary wire.

15. Most Painless kits do not come with any ground circuits. Usually this is not an issue, but with Corvettes, locating a good ground can be a bear. We made a ground harness for the rear taillights using ring terminals and 14-gauge primary wire.

 

16. The key to a good ground is a solid connection. The paint should be removed from the metal surface of the ground location.

16. The key to a good ground is a solid connection. The paint should be removed from the metal surface of the ground location.

 

17. Then the ground feed was bolted to the frame. We killed two birds with one bolt, using the fuel pump mounting point as the ground point.

17. Then the ground feed was bolted to the frame. We killed two birds with one bolt, using the fuel pump mounting point as the ground point.

 

18. Then the ground harness was routed to each light. The taillights ground on the mounting stud.

18. Then the ground harness was routed to each light. The taillights ground on the mounting stud.

 

19. Under the hood, we separated each wire group just as we did inside the car. There are a lot of small groupings of wire here, so it is important to take each one separate.

19. Under the hood, we separated each wire group just as we did inside the car. There are a lot of small groupings of wire here, so it is important to take each one separate.

 

20. As we laid each wire group out on the engine, the harness started coming together.

20. As we laid each wire group out on the engine, the harness started coming together.

 

21. To keep things neat and tidy, we used electrical tape to bundle groups and mark separation points from the larger bundle.

21. To keep things neat and tidy, we used electrical tape to bundle groups and mark separation points from the larger bundle.

 

22. Using Painless Performance’s PoweBraid wire loom, the entire harness was wrapped up. Where wires needed to break out of the harness, we cut a slit in the loom. This eliminates bulges in the harness.

22. Using Painless Performance’s PoweBraid wire loom, the entire harness was wrapped up. Where wires needed to break out of the harness, we cut a slit in the loom. This eliminates bulges in the harness.

 

23. We also used the special rubber tape from Painless to wrap up the ends of each loom section for a factory finish.

23. We also used the special rubber tape from Painless to wrap up the ends of each loom section for a factory finish.

 

24. The engine harness looks like it could be straight from the factory, although we think this looks even better than the way they come from Detroit. With patience and perseverance, your wiring job can look just as good.

24. The engine harness looks like it could be straight from the factory, although we think this looks even better than the way they come from Detroit. With patience and perseverance, your wiring job can look just as good.

 

25. The last step in any wiring job is connecting the battery. We went with an Optima Yellow Top, which is a deep-cycle battery. Becasue the Vette will likely sit in the garage for long periods, the deep cycle will last longer than a typical battery. We also wired it with the quick-connect for the new Optima Digital 1200 battery charger/conditioner.

25. The last step in any wiring job is connecting the battery. We went with an Optima Yellow Top, which is a deep-cycle battery. Becasue the Vette will likely sit in the garage for long periods, the deep cycle will last longer than a typical battery. We also wired it with the quick-connect for the new Optima Digital 1200 battery charger/conditioner.

 

Sources:

Painless Performance

 

About Jefferson Bryant (221 Articles)
A life-long gearhead, Street Tech Magazine founder and editor Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 5 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced. You can follow Jefferson on Facebook (Jefferson Bryant), Twitter (71Buickfreak), and YouTube (RedDirtRodz).

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