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The Best Wiring Solution for Your Hot Rod or Muscle Car Project

10/18/2022
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Wiring Your Own Car Is Not as Scary as You Think
This old OEM chassis harness might look scary, but rewiring your ride with a new harness can be done with a little patience and planning.

At a glimpse, installing an aftermarket electrical wiring harness may look like an overly complicated task. One reason may be that for most enthusiasts, mechanical work, such as replacing a carb and intake, or bolting on a disc brake conversion, is merely, at its most basic removing fasteners and hard parts and installing the new shiny/better versions.

Sure, there are some things to watch for like proper torque specs or having to know how to bleed brakes, but that is nothing compared to having to do any wiring repairs or upgrades for most. Electrical wiring, for some reason, scares a lot of people and we’re here to tell you it is not that hard with a little forethought and careful execution.

What Does It Cost to Rewire Your Car?
You can save a lot of money installing your own chassis harness. Money you can use for other aspects of your project build.

If you’ve ever tried pricing out the installation of a custom wiring harness from a professional shop, you’ll see that the average labor is anywhere from 20 to 40 hours. That hit to your wallet, with most shops charging well over $100 an hour these days, can shift your spirits around pretty fast. The truth is the wiring harnesses Speedway Motors offers were developed with the do-it-yourselfer in mind, saving you all that installation labor for other aspects of your project.

We’ve designed our harnesses for the average hot rodder to tackle as a weekend project. Every kit is supplied with a detailed set of step-by-step instructions, with each circuit pre-labeled directly on the wire so you don’t get lost. And with a bit of effort, a little patience to follow the instructions carefully, and taking each circuit one step at a time, anyone can do it.

How Many Circuits Do I Need in My Car?
Speedway Motors offers this unique 12 circuit chassis harness with a vintage cloth wrap appearance. It's great for early cars with open engine bays like T-buckets.

There are a few things to consider when you’re ready to purchase a wiring harness. To start, you should consider the number of circuits needed for your application. Typically, a basic 12 circuit harness is the perfect solution for small vehicles with minimal circuits. Vehicles like a T-bucket build, or a Model A hot rod for example. A great option is our cloth covered 12 circuit harness for that ideal period look for 1920s to 1950s cars. These 12 circuit offerings are deal for a wide range of early street rods that may only require the basic needs like the ignition, horn, lights, charging system, etc.

If you’re building something with a lot of accessories like an audio system, power windows, air conditioning, EFI/engine management options you’ll want to consider a wiring harness solution with sufficient circuits in the harness that would be more suitable for such a vehicle. Our 18 circuit and 21 circuit harnesses often have more than enough protected circuits to cover anything you can add to your ride. For those throwing the whole kitchen sink at their ride we even have a few 28 circuit harnesses to cover your electrical needs.

Where Do You Start with Wiring Harness Installation?
Bundling and routing your chassis harness is your first step to a clean and functional installation.

If you haven’t had any experience wiring a whole car before, one of the toughest parts can be getting started. You can start by laying out your harness on the floor. Familiarize yourself with the various wires and circuits. Then bundle them into the main groups of wires for specific areas in the car: dash switches, gauges, engine compartment, headlights, and taillights, and so on. Don’t be afraid to cut the factory tie wraps and reorganize the harness to better suit your car’s needs. Grab a cheap bag of “sacrificial tie wraps” and use them for harness bundling.

Make sure your fuse box is easily accessible for fuse replacement and does not interfere with wiper linkage, gas pedal, brake pedal, etc. under your dash.

Decide where to mount the fuse block, as this is the starting point for every wire in your harness. Typically, you will screw the box to a bracket or the body on a fiberglass car. Usually, the best place to mount the fuse block is under the dash on the firewall or some may mount it under the seats. You’ll want a place easily accessible that will simplify running the wires from the front to back of the car. If you took an existing harness out of your vehicle, hold on to it in case you need to re-use various pigtails or connectors that are specific to your vehicle.

Any time your wiring passes through a bulkhead, such as a firewall, use a press in rubber grommet to protect your wiring.

From the mounted fuse box route your wire bundles to their respective termination points. Most wiring will need to pass through metal at some point (firewall, rear bulkhead, etc.) so be sure to use rubber grommets anywhere your wiring bundle goes through such metal. Some wiring harness kits that are vehicle specific include cutting templates for wire bulkheads, fuse box, and other needs, so be sure to fully read the instructions before picking a location to pass wiring through.

What Tools Are Used for Wiring?
Do yourself a favor and splurge for a ratcheting wire crimping tool. They are much easier to control and prevent under or over crimping a connection.

Having a quality crimping tool is paramount to a solid installation and will make all the difference when you’re using solderless connectors to connect various wires in your harness. You will find both manual and self-adjusting wire strippers available to make stripping the wire ends quicker and cleaner too. Don't forget to add new connectors for a secure, long lasting electrical connection.

Covering your new wiring harness with split loom provides additional protection and great looks. We offer modern split loom as well as braided nylon and cloth overwraps.

For a professional look, you can use heat shrink tubing over terminals to protect and insulate the connections. Adding additional protection and appearance with wire coverings available in braided nylon, braided cloth, plastic split loom, and more, is a great idea too. OEM wire holders can be used to secure the wiring bundles to the firewall or frame, but if your original retainers are broken or missing a simple solution is to use insulated line clamps.

If you've never completely rewired a vehicle before, don’t panic. There are plenty of useful guides out there, like our How to Wire a Street Rod book. It takes you through, step-by-step, with fully illustrated instructions on how to wire-up your car. Also, if you’re working on a ’50s or ’60s era car, you can always refer to the factory repair manual for specific instructions to your vehicle, which are offered in reproduction form in print or digital formats.

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