Ls1 Easy Swap Fuserelay Box Use Your Ls1 Harness on Any Swap Vehicle

The wiring aspect of any LS swap is undoubtedly the most difficult. Most builders are familiar with fabrication techniques, trouble shooting, and parts swapping to make things work, but electronics rise to a much higher level of complexity. Wiring has carried an aura of mystery that can send a shiver down the spine of even the most seasoned builder, making them wish for a simple carburetor and distributor. If you fall into this group, don't lose hope. This chapter has the answers you seek with easy-to-understand instructions for tackling the wiring of an LS swap.

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Retrofitting the stock harness requires knowledge of electrical circuits, soldering skills, and attention to detail. It is not a simple plug-and-play procedure, so make sure you are up to the task before hacking into the wiring harness.

Gen III/IV engines feature complex computers that control everything from timing and ignition to fuel and air intake. On many LS engines, even the throttle is computer controlled; the pedal is connected to a sensor box that tells the throttle how much to open. These systems can be overwhelming, but the key is to tackle one circuit at a time. Although the factory systems are certainly adequate, the aftermarket has fully embraced the LS platform and there is definitely more than one way to do it right.

Wiring Harness Basics

If you picked up an engine from a salvage yard or other used vehicle, you need all the electrical components to go with it. Let me repeat: it is imperative to get everything. This includes the computer, wiring harness, mass airflow sensor (MAF), oxygen sensors, and if the engine is drive-by-wire, the gas pedal and throttle actuator control (TAC) module. Each engine requires the use of its own specific computer and harness, and keep in mind that there were changes made to each system year by year. In order to reuse as many of the factory components as possible, you need to get all of them with the engine. Matching key components such as a TAC module with the ECM can be tricky without all vehicle/engine-specific details such as year, make, and model.

A stock harness can be used asisin the swap, or can be given the "wire diet" by cutting off the loom and removing the wires that are not needed. This is a great way to get to know the engine's wiring in detail. Keeping track of each wire can be a bit of a headache, though.

Whether using a stock or an aftermarket harness, the cleaner the install, the better. This Painless Performance PowerBraid protects the wires from abrasions and heat while keeping a stock look.

Friction tape at the ends secures the braid. Regular electrical tape works, but make sure it is good-quality stuff such as 3M Super 33. The cheap stuff falls off.

Each Painless Performance kit comes with all the basics: terminal pack, relays, and zip ties. You often need more terminals than what is included, so be sure to have plenty of assorted terminals on hand. Bulk terminals can be ordered directly from Painless.

Here is the completed wire-diet LS1 harness install with the full loom. This takes some time to complete, but the results are worth it.

Retrofitting a stock wiring harnessis seemingly complex and perhaps overwhelming. In fact, it is really not that difficult. With the proper diagrams and instructions, it can be modified to greatly simplify the process of wiring the engine. The majority of the wires in the stock harness are not needed in a retrofit application. Seriously, what 1969 Camaro needs an evaporative canister purge solenoid control? There are differing opinions on what to remove from the stock wiring harness, however.

Wiring a Classic Corvette

Rat's 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 rewiring a muscle car, most gearheads just don't enjoy wiring. It doesn't have to be this way, though, as there are tricks and tips that can turn a nightmare into a job well done. And it doesn't require a degree in electrical engineering either.

There are two main types of wiring projects: fixing an existing system or replacing it. With 40-plus-year-old wires, often the best solution is total replacement, especially if the car is apart already.

The crew at Red Dirt Rodz handled all of the wiring details for this 1967 Corvette roadster. This car came into the shop as many do, fully disassembled, as one person's failed build sold off to another. Although the original harness was still there, most of the terminals were broken, the wires were cracked and corroded, and it simply was not worth trying to fix, especially considering the car was being fully rebuilt. Starting with a clean slate is always nice. One call to Painless Performance and the harness was on its way.

They could have ordered a factory replacement harness, which is already terminated and bundled, just like the factory harness, and every-thing is where it should be for the stock components. But that wouldn't work for this project as the roadster has an LS1, electronic transmission, aftermarket gauges, and all the new-fangled goodies found on a new car. This situation called for a new plan with new routing for this complicated wiring system.

The tools for wiring are critical. Using junky terminal crimps and dull cutters don't make it any easier. The most important tool 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 no good; throw them away. They are only good for emergency repairs. You need a set of good crimpers designed for insulated terminals. Klein Tools and KD Tools make excellent crimpers.

The first step is to break down the harness and split up the groups of wires.

Plan the layout of the harness before getting to the car.

It's very important to properly install wire terminals. A speed stripper really speeds up the process and is a worthwhile investment.

The key to a good crimp is quality crimpers. This pair works great for insulated terminals, the kind used on this car. They also work for non-insulated terminals.

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).

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

Next, locate where the engine side of the harness goes through the firewall. On the Corvette, we used the stock location. Be careful, as sometimes the chosen hole has another function.

The fuse box mounts to the firewall with two bolts. It can be a real pain to install the fuse box; having a helper alleviates a lot of frustration here.

The metal backup plate was trimmed to match up with the firewall.

Inside the car, the bundles of wire were split into groups and routed to their locations. Don't cut any wire until the entire harness has been routed.

This is the Painless 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, which were mounted under the center console in the Corvette.

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 easier.

All the main ignition wires are 12-gauge wire. These feed the majority of the electrical system. The key to safe wiring is using the proper-gauge wire for the amperage. The longer the wire, the larger the gauge needs to be.

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

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. Use a ground harness for the rear taillights; use ring terminals and 14-gauge primary wire to provide grounds for each light.

The key to a good ground is a solid connection. The paint should be removed from the metal surface of the ground location. If you can't remove the paint, a star washer is an alter-native, as it cuts into the metal as the bolt/screw is tightened.

Next, bolt the ground feed to the frame using the fuel pump mounting point as the ground point. By using the same bolt, the number of holes in the chassis is limited and it keeps everything neat and clean.

Then route the ground harness to each light. The taillights ground on the mounting stud. When using speed-nuts, you have to be careful not to over-tighten them or they strip.

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

As each wire group is positioned on the engine, the harness starts to come together. Keeping each circuit group together can be tricky, so be patient. The hardest part of wiring is the planning.

Selecting the correct wire size for the terminal is critical. Using a terminal that's too large results in a weak connection. Most terminals are color coded for size. Red is the smallest, fitting 22- to 18-gauge wire; blue is for 16- to 14-gauge wire, and yellow is for 12- to 10-gauge wire. Anything bigger is sold by the size, not color.

Primary wire is typically an 18-gauge wire and is the most common wire found in wiring harnesses. The larger wires that feed heavy-draw circuits are typically 14- to 12-gauge.

The wire in Painless Performance kits runs a little larger than the standard; the primary wires are 16-gauge, with 12-gauge for heavy-draw items such as the headlights.

Opening the box and seeing several thousand feet of wire 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. Painless kits come pre-bundled in all the major groups: engine, dash, and tail. From there, they are divided into sub-categories.

Another component used in Gen III/IV wiring is the Weather Pack and Metri-Pack terminal. These are small pins that require special tools to crimp. They are used in every connector on a late-model engine. Most builders don't have to deal with disassembling and reassembling terminals but if you are retrofitting a stock harness, you do.

The components of MetriPack or Weather Pack terminals are a Molex or nylon housing, a silicone wire seal, and the terminals. The housings are shape-specific; you must make sure that you have the correct male and female components. The terminals can sometimes be specific to the housing as well.

These are the crimpers used for the terminals. They are available in many configurations, and most have ratcheting locks for a completed crimp.

The terminals must be crimped twice, once on the bare wire and once on the silicone insulation. Make sure you slide the wire through the silicone boot before crimping.

Each terminal style has different pin types. All styles lock into the plug housing with spring locks built into the terminal itself. Unlocking these can be a pain; the trick is to use a small pick or unfolded paper clip to unlock it. Every terminal uses a different lock location.

The DLC or OBDII port is a must-have for any LS swap, and it is often overlooked when retrofitting a stock harness. Make sure you grab the wiring harness from the donor car. If you don't, you have to head back to the salvage yard or take your chances on eBay. (Photo Courtesy Street & Performance)

These are good for the typical project, but there may be a few wires that need to be moved to a different section. Now is the time to reroute any wires. Once inside 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, you need to alter that wire's routing as it is normally found in the tail section.

All Painless wiring kits provide only the power side of the circuit. Except for a couple of situations, you must provide all ground connections. Although this is typically a simple thing, Corvettes require some additional forethought, as fiberglass does not make a good ground. Pain-less Performance thought ahead on this one, and 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. A novice builder should be able to complete a basic wire harness replacement in three to four days. The more circuits and the more complications, such as EFI, audio systems, etc., the longer it takes. But if you take your time and plan out the locations of all the wires before cutting anything, your wiring project will look and function great.

Aftermarket Harnesses

All of the connector and relay data (pages 87–91) represent what can be done with an LS1 wiring harness. The pin-outs for the later models are included on pages 81–82, but each computer and engine has different requirements to make it operational. Drive-by-wire and displacement-on-demand engines make this more complicated.

A pre-made retrofit wiring harness is generally the best solution for any Gen III/IV swap. This puts all of the responsibility in the hands of technicians who have tested each harness and guarantee it is correct. A simple crossed wire can fry the stock computer, rendering it useless. In addition, purchasing an aftermarket wiring harness also affords the luxury of having access to trouble-shooting tech assistance. If you get into trouble with an aftermarket harness, simply call the tech line to get it going and save valuable time and money and potentially a dead computer.

Everything in modern drivetrains is electronic, so proper grounds to the transmission are important. A simple braided ground strap to the frame will do. This also helps reduce electrolysis in the cooling system. (Photo Courtesy Street & Performance)

The body needs to be grounded as well. Scrape the paint away from the metal at the grounding point or use a star washer for solid contact. (Photo Courtesy Street & Performance)

Some LS wiring harnesses include the underhood fuse box. Bolt this down in a convenient location. If you are using an aftermarket harness without a fuse box, make sure that the power wires are properly fused. (Photo Courtesy Street & Performance)

Anytime wiring is run through the body, a grommet is required. This protects the wiring from chaffing on the body, causing grounds and the possibility of fires.

These wires are the stock ignition connectors for most GM cars. The big purple wires connect the relay to the starter. This is the quickest way to connect the vehicle's ignition switch to the LS starter.

The plug-and-play nature of an aftermarket harness combined with its relative affordability makes it the best option, plus it generally looks better than a hacked-up stock harness. Another thing to consider is that many factory harnesses are fairly old. With age, wiring becomes brittle and corroded. An aftermarket harness is all new, so the swap gets more life out of the wires. It's also impossible to know if the computer and harness were removed with care or yanked out, which can damage the wires and connectors.

Ordering a Harness

Most aftermarket harnesses are similar in their connections; it is the finer points of the finish and overall look that separates them. Many after-market harnesses are left in loose form, that is, without any loom or wrap on the wires. Certain wires are grouped together for their placement on the engine, such as the fuel injector harnesses, but that is as far as it goes. This leaves it up to you to cover the harness for the final finish.

Some aftermarket harnesses group each set of wires together as they are on an engine, and complete the job with wire loom or tape, making it a clean, out-of-the-box installation. If any of the stock components have been changed or moved to another location, the harness may have to be altered, so that is some-thing to think about before ordering.

To make sure you get the correct aftermarket harness, there are a few things to consider before placing an order. First, identify the engine and computer, whether it's an automatic or a manual transmission, and if the particular transmission is electronically controlled.

Old-style automatics, such as the TH350, and manuals such as the Muncie M22, are not electronically controlled, but the 4L60E automatic is electronically controlled. That is important because it must be connected to the computer. The MAF sensor is either a three- or five-pin (make sure to get this information from the donor vehicle).

Determining if the throttle body is drive-by-cable or drive-by-wire is also essential.

The type of fuel injector is the last piece of component information you need. There are three types: the old-style STD injector (which has a large metal bale clip), the T-style injector (which uses a Delphi 45 plug), and the Flex Fuel injector (which is also known as the Z-style). LS engines are plug-and-play, so installing the harness is quite simple.

Gauges

Once the engine is wired up there are still those pesky little accessories, such as gauges, that need to be connected. Since the original vehicles were so heavily dependent on the computer system, all the gauges were routed through the computer. Although this is fine for a 1999 Corvette, most older muscle cars require significant modification in order to retrofit late-model computer-controlled gauges.

Each drive-by-wire engine requires its own specific pedal, throttle body, and possibly TAC module. This is an LS2 kit for a GTO. The small box on the lower right is the transmission control module (TCM). (Photo Courtesy Street & Performance)

Most aftermarket harnesses are purely plug-and-play: just plug it in, make four wiring connections, and, theoretically, fire up the engine. Know the specifics of your engine and transmission before ordering, however, as there are a lot of options. An un-loomed harness allows rerouting of any wires to components that may have been moved.

There are three types of fuel injectors. Shown from the left: flex-fuel Z-style, old-style STD, and Delphi 45 T-style. Flex-fuel engines have the Z-style, and the other two were used across years, makes, and models. (Photo Courtesy Street & Performance)

Even throttle-by-cable throttle bodies have wires. The throttle position sensor and MAF sensor must be plugged in. The MAF sensor mounts directly in front of the throttle body. It can be moved with elbows and other induction piping components. There are three types of MAF sensors: three-pin, five-pin, and LS7-style. They are not interchangeable without ECM changes. (Photo Courtesy Street & Performance)

Throttle-by-cable is the most compatible with older transmissions because the brackets are already there for the kickdown or TV cables. (Photo Courtesy Street & Performance)

A cable-driven speedometer does not do much good with a VSS wire attached to it; neither does a stock 1965 tachometer. Special considerations that must be made in order to get the information from the engine to the driver.

Tachometer

Tachometers are simple gauges that measure the revolutions per minute of the engine. Although not absolutely necessary they are particularly useful, especially in manual transmission cars. If you're driving a car aggressively, you need to know how hard the engine is being worked.

The coil packs for Gen III/IV engines are very good from the factory, so there is no need to replace them at all. Their failure rate is very low. You would be hard pressed to find a dealer that has seen any failed coils. (Photo Courtesy Street & Performance)

Getting the tach signal to an old stock tach requires an adapter. The signal is modulated at a different rate from that of a typical V-8 tach. The LS signal must be converted to a standard signal with a module. These modules are available from Dakota Digital. Their SGI-8 module converts the tach signal to different settings, such as 4- or 6-cylinder. The tach signal coming from the LS1 is representative of a 4-cylinder signal. Therefore, a factory 6- or 8-cylinder tach must use this module to read the correct signal and display the proper reading.

Programmable tachometers such as an AutoMeter or VDO do not need this module, as they can be set to read a 4-cylinder tach signal.

Speedometer

With an electronically controlled transmission, an electronic speedometer can receive the signal from the VSS system via the computer, or an aftermarket speedometer can receive a direct signal from the VSS system. If the stock cable-driven speedometer is being used with a late-model transmission, the transmission must be adapted to drive the cable.

From left to right: K&N air filter, three- pin MAF, 90-degree elbow with three-pin MAF, and five-pin MAF. (Photo Courtesy Street & Performance)

If you're running a carbureted LS engine and a late-model electronic transmission, you need a transmission controller. This 4L60E/4L80E controller from TCI provides precise control and solid shifting of electronic automatic transmissions.

 For 4L60E and T56 OEM trans-missions, this is not a huge problem. Street & Performance offers replacement cable-driven tailshafts. Most aftermarket transmissions already have a cable-drive provision.

Oil-Sending Unit

The oil-sending unit also requires adapting. The oil cooler bypass fitting on the oil pan just above the oil filter is an ideal place to install an oil-pressure fitting for the sending unit. Depending on the specific engine, select one of three bypass fitting options: a drilled and tapped fitting; a blank boss fitting, which can be drilled and tapped; or a dome top fitting.

Although not strictly a part of the wiring, you need sensor adapters such as these if you plan to have any kind of engine monitoring that is not wired to the ECM. From left to right: adapters for coolant temperature, oil pressure at the block, and oil bypass. (Photo Courtesy Street & Performance)

The 1997–2004 Corvette engines have a drilled and tapped 1/4-inch pipe thread from the factory, and the 1998–2002 F-Body pans have a boss, but it is not drilled or tapped. The 2005-up engines have a domed cap with no boss. Any of these can be used. If you need to drill and tap the fitting, simply drill it and tap it to the thread size that the oil-sender fitting requires. You can also use the 16-mm threaded hole behind the intake manifold with an adapter that converts to 1/8-, 1/4-, 3/8-, or 1/2-inch NPT threads for the oil-pressure sending unit.

Drive-by-Wire

The drive-by-wire system is a potentially confusing portion of the wiring conversion. Each engine that uses the drive-by-wire system requires a specific pedal, throttle body, and, in some cases, a TAC module. In most cases, the drive-by-wire components are not interchangeable. The pedal, TAC module, and throttle body must remain with the engine in order for it to work properly. The only interchangeable components are the Vortec truck modules, but the programming in the computer must be changed as well. There are several different component packages, which vary by vehicle.

The 1997–2004 Corvette uses a pedal and separate TAC module to operate the specific throttle body. In 2005, General Motors went to a drive-by-wire pedal that incorporated the TAC sensor in the pedal, so only the pedal and throttle body are needed for a swap. The same goes for the 2005–2006 GTO, which uses a specific GTO-pedal-only configuration. Chevy SSR trucks use a dedicated drive-by-wire pedal with a TAC module. The Cadillac CTS-V uses a pedal and TAC module up to 2004, when it switched to a pedal only in 2005-up. The 2007 Trailblazer uses a pedal only and is different from the rest of the trucks.

Vortec-powered trucks with the adjustable pedal system are not suitable and must be adapted for use with  conversion engines. These trucks use a drive-by-wire pedal mounted on a moving platform that adjusts to the height of the driver. Of course, you could simply swap to a cable-driven throttle body or a carbureted setup for one of these engines.

The trucks' pedals and TAC modules are very confusing; General Motors seemed to do a lot of different things with the trucks over the years. Drive-by-wire was first avail-able in the trucks in 1999, and there have been many different pedals with and without TAC modules. This is why it is so important to get all of the components from the donor vehicle beforehand. If you didn't grab the pedal (not everybody thinks to grab the gas pedal when doing an engine swap), you can purchase one from any GM dealer, salvage yard, or even a few aftermarket shops, but you need all the details for your particular engine and ECM.

Feature Vehicle: Volvette – A Corvette-Engined Volvo

Photos courtesy Doug Strickler

This Volvette started out as a daily driver for Douglas Strickler's dad, Dale Strickler. He spent many years as an avid Volvo enthusiast. When Dale passed away in 1999, the rest of the Strickler family decided to give the 1989 Volvo 740 Turbo Wagon to Doug. Having been around Volvos for years, Doug started playing with the wagon, modifying the stock turbo 4-cylinder.

Eventually, Doug couldn't extract much more performance without sinking a lot of additional money into it, so he decided to change power plants and installed an LS1. The reliability, ease of use, and the obviously larger aftermarket were all a part of his decision. Of course the wagon still had "turbo" badges on it, and Doug figured there was no reason to give them up. The build was on, and Doug certainly had his hands full.

Mounting the LS1 in the Volvo chassis was the most difficult part of the entire swap. The motor mounts were hand fabricated, along with a completely custom crossmember built from 1/8-inch plate steel.

The trick to fabricating custom motor mounts is to suspend the engine over the frame where you want it to be. This can be done with the engine on a hoist and setting blocks under the engine to secure it. The hoist supports the bulk of the weight.

Another option is to use a plastic engine block from Pay-R. These lightweight plastic engines are dimensionally accurate and are a great way to safely lay out motor mounts for custom installs.

The engine needed to sit back as far as possible toward the firewall to allow room for the turbos to clear. The transmission crossmember was built in a similar manner, using 1/8-inch plate steel.

As a turbo enthusiast, Doug figured if one is good, two is better, so he opted for a pair of 60-trim Garret T4 turbos to straddle the LS1. Doug built everything on the Volvo, and Carolina Auto Masters tuned it.

Currently, Doug drives the car daily and enjoys 30 mpg on the highway. The Volvo makes 544 hp at the rear wheels and has no drivability issues. To support the turbos, an Aeromotive A1000 fuel pump feeds the 42-pound fuel injectors.

To eliminate accessory drive issues, Doug built his own system. Part of the turbo brackets double as the accessory drive mounting. This swap is about as custom as they get; very few aftermarket pieces were used and everything was custom made.

The T56 is coupled to a performance-built Ford 8.8 rear end with 9-inch 32-spline Strange axles, bearing girdles, and 4.10:1 gears. Doug says he likes the deep gears because the power output is big enough to move the car as fast as he wants to go, and it lets him shift a little less. The Volvette has traveled the quarter-mile to the 11-second mark. Not bad for the ol'grocery-getter.

Written by Jefferson Bryant and Posted with Permission of CarTechBooks

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