K.J. Jones
May 1, 2007
Trevor Kaplan (left) and Saul "The Surgeon" Gutierrez designed and set up the wire trail by which 12 volts of Optima battery travel around our project car.

Horse Sense: You may have read Hot Rod's cover story on Drag Week 2006 by now and are wondering why there's no mention of our project T-top coupe in the extensive report on the five-day, 1,500-mile, street/strip challenge. Unfortunately, we didn't complete the project with enough time to test the car before embarking on such a major journey, as getting to Drag Week from SoCal is an 1,800-mile trip. The painful decision was made to miss the event and set our sights on being a part of the Drag Week action in 2007.

In our last report on the project car ("Plumb Assignment," April '07, p.148), we gave you some insights on high-performance plumbing and hopefully provided ideas on how to facilitate proper flow for fuel, air, exhaust, cooling system, and so on, in a street/strip 'Stang. This month, we're taking a look at our T-top coupe's electrical system-more specifically, the creation of its electrical system.

Rear-mounting the battery is a standard for street/strip 'Stangs these days. We're using Moroso's sealed battery box (PN 74050), featuring a 10.5x13x9.5-inch polyethylene box, a vent tube, NHRA-approved 3/8-inch hold-down rods, and all the hardware necessary for a clean installation in our coupe's trunk.

Those of you who have been faithfully following the project already know we've been rebuilding our Mustang from the proverbial ground up, as we detailed the actual stripping of the coupe in one of the early installments of this build series. The reconstruction process included adding several different high-performance parts that operate on 12 volts, so it's time to establish a way to power all of these necessities and accessories to make the 'Stang operational.

Wiring any car, be it a stocker, a fairly radical street/stripper such as ours, or a full-on NMRA racer, requires a lot of thought and attention to detail. When talking about voltage, it's critical to focus on doing things right. Cutting corners with materials or the execution of putting an electrical system in the car can have catastrophic consequences, so make sure you have a good plan before you begin laying out the wire. Most of us are guilty of using the wrong gauge wire for a particular application or wiring a 12-volt component to power without adding a fuse or relay to the circuit at some point in our lives.

Our from-scratch, weekends-only wiring job took the better part of a month to complete, but we're pleased with the way it finished.

A Painless Performance Products switch panel and wiring kit is the foundation for our coupe's electrical system. We used Scosche Industries' 0-, 4-, and 8-gauge EFX Powerwire and terminal connectors to channel power to and fro. We installed all of the 'Stang's 12-volt-dependent paraphernalia, including the aforementioned ignition and engine-management stuff. By taking our time, we were able to achieve a factory-clean look and get everything running that requires power-including lights, horn, and wipers, among other things-without any problems.

Something that deserves mentioning with respect to wiring any vehicle is the importance of establishing good grounds. It's often overlooked by enthusiasts who delve into hooking up fuel pumps, nitrous units, and other things themselves; failure to pay attention to the need for proper grounding can bring on major frustration. The high resistance caused by improper grounding can lead to an accessory operating poorly or not at all. In some cases, a bad ground can lead to an electrical fire.

For power, Optima's Yellow Top deep-cycle battery (PN D35 YT) kicks out 650 cold-cranking amps and is perfect for Mustangs like ours, which include several critical components that require full and consistent voltage for optimum performance.

We took great care to make sure our coupe and its electrical components are grounded well and all the wire-to-wire and wire-to-terminal connections are secured with solder and protected with shrink tube.

Wiring a 'Stang is a daunting but doable project. The key is to have a good plan before you begin. If you think its best to have a professional wire your steed, companies such as Wires and Pliers (www.wiresandpliers.com) and Spaghetti Menders (www.spaghettimenders.com) are dialed-in when it comes to Mustangs-especially hard-core, drag-race 'Stangs. Either company can set you up with wiring harnesses tailored to your Pony's specific, electrical needs.

A complete breakdown of everything we had to do on the electrical side to get our '86 Mustang running could take all the pages in this magazine. Since we don't have that kind of space, here's an assortment of photos and a couple of sidebars that highlight how our project's electrical needs were handled, as well as offer a few tips and tricks on how to lay out the electrical plan for your ride.

A quick lesson on alternators: The alternator converts the engine's power, which is transmitted through a belt and pulleys, to electrical energy to maintain a sufficient charge in the battery. PA Performance makes this 130A 3G alternator (PN 1619-6B1). We selected it mainly because of its impressive charging capacity, which is three times greater than that of a stock alternator. Adding a 3G conversion plug (PN 46280B) is mandatory for our 'Stang, since it no longer has any original wiring. Our supercharged application requires a six-rib pulley, but PA units are also available with pulleys for four-, five-, seven-, and eight-rib serpentine applications.

A battery-cutoff switch is required equipment when the battery is mounted in the trunk or hatch area. Since the coupe will be driven on the street, we needed to establish a happy medium between the kill switch-which we planned to mount on the car's rear panel- and the license plate. Using an old plate as a template, we drilled a hole through it and the panel in the location where the switch will reside. The new plate will be altered accordingly when the car is registered. Keep in mind that drilling holes through license tags or modifying them is unlawful in certain states and could result in steep fines. We decided to take that chance for the sake of a clean look.

This Flaming River combination battery/alternator kill switch (PN FR 1013) will completely shut down the battery and charging system with one firm press of the red knob. This piece is neat because its green/red color-coding lets us know when power is hot and when it's not. With its spring-loaded knob, the switch can only be clicked in one direction to turn power on.

After running our 0-gauge battery wire from the trunk to the front of the car, we connected the main power feed to this standard, two-post, starter solenoid mounted in the engine compartment. While this part's primary job is to transfer power to the Powermaster XSTorque starter (PN 9503), it can also serve as an underhood power point for various accessories. Note how our main power (secured to the left post) enters the engine bay from the outer side of the fender. This was done in an effort to make the engine stand out and keep the visible wiring to a minimum.

We thank Dennis Overholser of Painless Performance Products for his help with selecting the right stuff for our project car's electrical control center. Saul "The Surgeon" Gutierrez checks out the rocker switches, universal Ford chassis harness, and various other relays, diodes, and components that comprise our Painless system.

Wiring a 'Stang can be intimidating. Of course, function is everything when it comes to throwing power around, but these days, street- and race-car electrical systems are expected to meet certain appearance standards.

Long gone are the days of hiding a disorderly jumbulation of wires under the dash with zip ties, using butt-connectors for everything, or using same-color wire for an accessory's positive and negative leads.

Today, wiring is about organization. An organized electrical system isn't only going to be a benefit to you and your car from an appearance standpoint, but it will also prove to be an invaluable quality if or when the time comes to troubleshoot electrical-related problems with the car.

Painless Performance Products offers several wiring systems that are tailor-made for Fox 'Stangs and include an easy-to-follow schematic that will have you wiring your Pony like a pro.

Trevor Kaplan of Scosche Industries was our electrical wizard for this portion of the project, and he set up the 'Stang with an electrical system that uses the Painless kit and Scosche EFX Powerwires of various gauges.

Florida 5.0 has developed trick, Fox-Mustang, ready-to-drop-in instrument clusters available for '79-'86, as well as '87-'93. We have the race version that doesn't have openings for vents or HVAC controls. Florida 5.0 also offers several specialty pieces and clusters/gauge panels for '94-'04 Ponies. The company laid out a combination of Auto Meter's Sport-Comp II Series that includes 211/416-inch full-sweep, electric boost (PN 3659), oil/fuel pressure (PN 3653 and 3663), water temp (PN 3655), transmission-fluid temp (PN 3657), volts (PN 3692-short sweep), and fuel-level (PN 3615-short sweep) gauges. A Sport-Comp II 331/48-inch tachometer (PN 3697) and speedometer (PN 3688) keep us informed of the 347's vitals and our highway speed. The cluster also features a shift light, turn-signal indicators, a red beacon to let us know the Roll Control is on, and a blue beacon for the high beams.

The Painless Performance Mustang Power Panel (PN 50210) is designed for mounting in the stereo location of '79-'86 Mustangs. But since the Florida 5.0 cluster doesn't have vent openings or any provision for installing HVAC controls, we decided that our coupe's Sony GIGA Panel stereo unit (PN MEX-1GP) will be installed in the factory-designated spot, and the switches will be mounted in the flat area on the right side of the faceplate. By doing this, all the engine, fan, antiroll, and transmission controls (transbrake, converter lockup) will be within easy reach. Two additional rocker switches for the headlights and wipers will be installed in the flat portion on the far left side of the faceplate.

Saul uses a Dremel to cut an opening in the Florida 5.0 gauge cluster. Our panel was set with a carbon-fiber overlay, so it's important to take extra care when slicing through it.

The instrument cluster's outer beauty is apparent, but the real magic is on the back of the panel. Florida 5.0 lays all the groundwork for an easy installation by adding wire and the appropriate connectors, and basically creating zip-tied harnesses for all the gauges in the cluster. Each wire is labeled to identify where it should be connected, which is a big help-especially when you're doing this for the first time.

Relays similar to these are the most overlooked components of a street/strip 'Stang's electrical system. The collective amp draw from fans, water pumps, solenoids, ignition system, stereo equipment, lights, and other things, will be fairly high in our project car. Even though the Painless and Scosche EFX wires are the proper gauge for what we're doing, a lot of heat will be generated. We're using relays to energize some of the electrical components with shared voltage. For example, via a relay, our FAST XFI engine-management unit will send a triggering voltage to turn on the Aeromotive fuel pump when the ignition is energized. Relays basically replace switches in situations where there is voltage available to activate a device. It takes about 150 milliamps to trigger a relay. We're using 30-amp relays for most of the coupe's electrical makeup, and Scosche's big-dog, 100-amp relays to keep heat out of the switch panel's circuits.

This on-off-on rocker switch controls the radiator- and trans-cooler fans, as well as the Meziere water pump. In one "on" position, the fans and water pump will run at the same time. The other "on" position is dedicated to the water pump only, so we plugged a Painless racing diode (PN 80111) into the switch to make this type of isolation possible. The diode works as a check valve of sorts; it lets power flow only in one direction. We're using another rocker-switch/diode combination to run the coupe's parking lamps separately or together with the headlights.

We took a note from many of the NMRA-race Mustangs we've seen and mounted two Moroso momentary switches (PN 74122) in the left spoke of Grant Products' Evolution GT steering wheel (PN 1434). The buttons are for our burnouts and launch at the dragstrip. The top switch controls the Performance Automatic transbrake, and the button below is for activating the Moroso antiroll solenoid.

We used this simple four-pin plug from a trailer-wiring kit to channel electric signals from the transbrake and antiroll control unit to the Moroso momentary switches mounted in the steering wheel.

The electronic speedometer requires Auto Meter's 16-pulse-per-revolution Hall Effect sending unit (PN 5292). The pass-through drive for cruise control is blocked off (red cap) since our coupe doesn't have that luxury.

Although the coupe's electrical system is tied into several relays, we still use fuses. This ATC Fused Power Distributor by Scosche (PN P48ATCFDI) is a platinum-plated hub for a four-gauge power feed that breaks out into four fused, eight-gauge leads for the fuel pump and other accessories.

As we mentioned earlier, every stitch of factory wire was removed from the coupe at the onset of the project. With that being the case, new harnesses for the front and rear lightworks had to be created, although we saved and reused all the bulb sockets from the OEM wiring. Bobby Lourenco helped us in that department, using Scosche's trick EFX twisted, nine-wire cable. The cable consists of nine color-coded, 18-gauge wires wrapped in a clear jacket, and it's perfect for making this type of harness.

We're using a FAST XFI engine-management system and MSD's 7531 Digital-7 Programmable ignition box to light the fire in our T-top coupe's Paxton-blown Keith Craft 347. These two devices are, without question, the most important 12-volt-initiated components in the car.

While installing these two systems isn't difficult, we've decided to personalize things by not putting the boxes in the coupe's passenger-side footwell-a common location for race 'Stangs. The custom install will maintain a street-car look for our interior and enable a copilot to sit comfortably in the second seat.

FAST makes harnesses for its XFI engine-management systems that can be custom-ordered and made for a 'Stang's specific needs. You can probably make your own harness, but this setup is plug and play, and it fits perfectly in the engine compartment. We began by laying out the harness and finding all of the connector locations on the engine.

The holes in the coupe's firewall were filled and smoothed over during the body-and-paint phase of the project, so a 2 1/4-inch opening had to be bored into the firewall to pass the XFI wiring between the engine bay and the passenger side of the coupe's interior. Once the harness is in place, the large, rubber grommet seals off the firewall.

All of the XFI's connections are made with weather-pack couplers similar to this one. This locking-style coupler guarantees solid communication between sensors and injectors, as well as the XFI processor, and protection against water, dirt, and other matter that could cause the XFI to malfunction.

Since we're not using a glovebox, we mounted the XFI processor on a piece of sheetmetal that was sized to serve as a glovebox-delete panel. With the processor in clear view from the driver seat, we can keep an eye on the 347's firing activity via the LED bulbs running along the face of the XFI unit. The wires that connect to the XFI can only be plugged in one way, so there's minimal chance of messing up. Think square peg, round hole.

Editor Turner was supposed to make the Drag-Week journey with your tech editor, and keeping him comfortable was of the utmost importance. In an effort to keep the project 'Stang passenger friendly, we decided against mounting the MSD Digital-7 Programmable ignition box (PN 7531) in the passenger's footwell. Since the coupe's original center console was beyond restoration, we used it as a stunt console and cut it to mock-fit the MSD in the opening for the e-brake handle.

Our buddy, Jeremy Thompson (aka "V8Only"), whom we know through the popular Web site www.foureyedpride.com, set us up with a '79-'86 center console that's in much better shape than the T-top car's original piece.

Bobby uses Omni-Pak spray-on interior dye ("Tech Inspection," Mar. '07, p.180) to color match the Black replacement with the rest of the Charcoal Gray interior, then Saul uses the template made from the original to open the new console for the ignition box.

The wiring for our 7531 runs below the carpet, similar to the way it's done for most of today's new vehicles. We cut small, pass-through slots in the carpet and the console's mounting plate for the MSD, which helped us complete the ignition's below-console wiring connections and keeps things clean inside the car.

We covered the tech specifics on this bad-boy ignition in our Feb. '06 issue ("Bite in a Box," p.126), so we suggest you reference your 5.0&SF library and check out the details on what the Digital-7 Programmable is and all that it can do for your street/strip 'Stang.