Mark Houlahan
Tech Editor, Mustang Monthly
April 21, 2014

When building a dedicated race car for competition use—one that will always be trailered and never be used on the street—it’s imperative that the wiring system not only be kept simple but be easy to access for quick servicing. Using the factory wiring—while an option—is often discouraged due to many factors, including age, weight, routing, and excess circuits that are not needed in a dedicated race car. You can save several pounds by removing the old wiring harness and replacing it with a dedicated race car harness. Not to mention for the Fords we mess with many use ancient glass fuses with not enough circuits to properly control a typical race car’s electronic diet of electric pumps, fans, ignition systems, and more.

Besides the obvious weight savings and modern circuit protection, dedicated race car wiring also allows easier servicing with longer wire lengths to allow the fuse box to be mounted in an easy to access location versus the stock fuse box, which is often buried up under the dash somewhere. Having the fuse box mounted on the trans tunnel, dash, or rollbar means quick access to fuses and relays, which could mean the difference between making the next round and being stuck in the pits while your class makes its runs. Race car wiring systems also feature easy access switch panels for all of the race car’s critical systems, including fuel and water pumps, ignition, lights, and more.

Painless Performance Products is a household name when it comes to automotive wiring. From street rods and kit cars to replacement muscle car harnesses for classic Mustangs and other Fords, Painless has a wiring solution. So it’s no surprise that when it comes to wiring your dedicated race car project that Painless has you covered here as well. Painless offers builders quality race car wiring harnesses and accessories like trunk-mount battery cable kits and more to ensure your race car is wired properly and with the minimum of effort.

The 1967 Fairlane you see here is owned by Rusty Gillis, a former Super Stock racer who at one time held the NHRA SS/GA mph and e.t. records in his ’69 Mustang (featured in Modified Mustangs & Fords way back in our Dec. ’07 issue, you can read the feature story HERE. Rusty’s ’69 Mustang has been restored and the car is too valuable to take down the track anymore, so he decided to build this Fairlane to help him scratch his 1,320 itch. The Fairlane will be FE powered, just like his Mustang. The chassis setup work is complete, the paint is immaculate, and now Rusty is ready to wire the car and install the drivetrain. We’ll be installing the Painless PN 50005 10-circuit race car chassis harness with switch panel for rollbar or in-dash mounting. Check out the captions to see just how easy it is to wire a dedicated race car harness in your project.

1 The Painless 50005 chassis harness features a compact fuse/relay panel that is fully labeled with all circuit information and generous wire lengths. The included switch panel can either be dash mounted or rollbar mounted with the included mounting box (hose clamps not included). Painless provides plenty of tie-wraps, terminals, and a 70-amp main fuse.

2 When you trunk-mount a battery you need some serious cables to carry the electrical load. Painless Performance’s battery cable kit (PN 40100) and ground strap kit (PN 40140) will ensure the starter gets all the power it needs and the battery is properly charged.

3 Besides the main chassis wiring Painless can also provide any electrical or wiring hardware for your wiring project. We ordered some bulk wire lengths for future gauge wiring, a grommet kit (PN 71901), a weatherproof extreme terminal kit (PN 40065), and a Painless Performance’s brand-new roll over wire crimpers for crimping non-insulated terminals (PN 70900).

4 Another new product Painless has just released that we felt would be a perfect complement to the Fairlane’s wiring project is its new Classic Braid Wire Wrap. The “cloth” appearing covering has a nice nostalgic/vintage flair that works well with the car and Painless offers it in a complete chassis kit (PN 70970) with plenty of wire wrap for different harness diameters and even includes shrink wrap and self-vulcanizing tape.

5 We determined one of the best locations for quick and easy fuse/relay access would be the glovebox area. Using a section of stainless sheet from another project we used our Eastwood sheetmetal brake to fabricate a U-shaped bracket to sit behind the glovebox door.

6 The stainless sheet mocked up behind the glovebox door shows roughly how we plan to mount the fuse/relay block. The glovebox catch interferes with fitment however, but we have a plan.

7 A quick pass with our Miller plasma cutter makes the necessary clearance for the glovebox latch.

8 Once the necessary clearance was made for the glovebox latch the panel was bead blasted for a nice satin finish and secured using some existing holes in the dash structure.

9 The fuse/relay panel is then installed to the fabricated mount via the two attaching screws used for the panel’s metal backing (which was removed for the mounting shown here).

10 Using a loaner aluminum racing seat similar to what will be in the car Rusty positioned himself in his normal driving position so that the rollbar mounted switch panel’s position could be determined.

11 A quick indexing mark with a silver Sharpie was made while Rusty held the mounting box in his preferred location.

12 The rollbar mounting box includes several hose clamp slots to allow the box to be mounted to various diameter tubing. The box is also outfitted with wire pass-through openings on each surface. All holes were plugged with the included plastic plugs except for the right side opening, which we installed the included grommet into, as can be seen here.

13 As noted earlier, hose clamps are not included. However, the mounting box does not utilize any special clamp requirements, so your traditional worm drive hose clamps that are found at any parts store (and you probably have several in the drawer of your toolbox) can be used. Note the lip on the mounting face of the box that the switch panel hooks into should be at the top.

14 The switch panel comes pre-wired from Painless Performance, finishing a good portion of the wiring job for you. Simply pass the unterminated harness end through the grommet and feed the wiring through until the switch panel can be seated and secured with the included mounting screws.

15 Using some of the wiring kit’s tie wraps the harness from the switch panel is secured to the rollbar top hoop and then down the vertical bar toward the glovebox. These are “sacrificial” tie-wraps that are simply used for rough-in, as we will be covering all wiring with wire wrap.

16 The loose fuse/relay panel wiring is roughed in next. Here we’ve sorted the wiring as to its routing in the chassis. The wiring over the door jamb will route forward to the engine bay, the wiring lying over the door bar will go to the trunk area, and the wiring in the middle is extra accessory circuits we’re not wiring at this time.

17 Working with the rear harness first the wires are routed through the cowl side area into the door sill trough and to the rear quarter panel area. A body plug was removed and one of the Painless wire grommets fitted to pass the wiring through the inner structure and on to the trunk.

18 At the rear of the car the wiring is cut to length for its intended circuit (taillights, fuel pump, ground, and hot lead from the battery). Here the hot lead is cut to length, a ring terminal fitted, and shrink wrap sealing the end. This will go to the battery cut-off switch.

19 After completing the rear circuits it was time to wrap them. The wire wrap installs much easier if you purchase the Painless Performance tools. The plastic tools make the job simple and stress-free. Start by placing the wires to be wrapped in the center of the tool as shown.

20 Rotate the tool’s sleeve to “lock in” the wire bundle. This will allow the tool to be pulled along the length of the harness without popping off of the wiring.

21 Start the wire wrap over the orange “tail” on the tool at one end of the harness and ensure you have the first few inches of harness properly covered. Pull the tool along the harness while keeping your finger loosely over the orange “tail” and the tool will split the wire wrap to allow the harness to drop right into it.

22 Included in the wire wrap kit are shrink wrap and self-vulcanizing tape. The shrink wrap is perfect for wire ends and to keep the wire wrap from fraying, but for connectors that are too big for shrink wrap, or to secure wire “tape outs” and to prevent the wire pulling out of the wrap the self-vulcanizing tape is the perfect answer. Give it a nice pull as you wrap it around itself and it will vulcanize to its own surface for a strong seal.

23 The battery cable kit is a must for trunk mount battery setups typical to a race car setup like this. The ground cable comes out of the kit with the battery terminal already in place. Simply route it through your battery box and install the included ring terminal end secure to a solid ground.

24 For the positive cable it too is shipped with the battery terminal end in place, however, if you are using an external battery shut-off, like Rusty is, you’ll have to pick up a few extra 1-gauge terminals to be able to cut the battery cable and wire it to the shut-off switch properly.

25 The terminal ends can be crimped onto the bare wire ends, or if you have a propane or map torch you can heat them and apply solder to the terminal.

26 The battery cable kit includes shrink wrap in red and black to properly seal the terminal ends as well.

27 The completed battery cable routing in the trunk is neat and clean. The positive cable is routed through a factory hole and a pair of Painless Performance wire grommets and then travels forward to the starter solenoid under the car, secured by rubber coated clamps.

28 The harness between the switch panel and fuse/relay panel utilizes a quick-connect setup. The harness, once it is routed, is cut to the proper length and the included non-insulated terminals are crimped into place using the new Painless Performance crimper.

29 Carefully following the included instructions the connector wiring is inserted into the proper location in the backside of the connector until each wire locks into place.

30 Moving on to the front half of the harness, a small hole is drilled in the firewall for the engine compartment wiring to pass through. A grommet was used here as well, although we found it easier to pass the wiring through the bare hole first and then slide the grommet down the wires to the firewall where it was pushed into place with a small pocket screwdriver.

31 Routing the wiring forward the first connection made was to the starter solenoid. Each wire is printed with the wire’s routing information so it is very difficult to connect the wrong wires. Between color coding and the wire printing wiring any car can be a breeze.

32 The blue with yellow striped wire is the chassis harness feed for the headlights. Here the wire is passed through a small grommet in the core support and then looped back through the same hole. This will allow us to wire the passenger side headlight while the looped back wire will be routed over to the driver-side headlight.

33 The loop is cut and a solderless terminal installed with a quality pair of crimpers. The headlight’s low beam circuit is stripped of insulation and then crimped within the solderless terminal as well. The high beam wiring will not be used and ring terminals were crimped onto the headlight’s ground wires and grounded right at each headlight.

34 A length of shrink wrap is used to seal out all crimped connections, like the headlight circuit we just completed.

35 Once the forward portion of the harness was routed the wire wrap was added to the wiring for a clean engine bay appearance. The blue wire looped over the shock tower is for the engine’s electric water pump. As you can see, the engine is not installed yet, so we’ll have to revisit the project down the road once Rusty has the engine in place so we can wire the electric water pump, electric cooling fan, and a few necessary gauges. Stay tuned.