As with other LS components, a massive number of computercontrol, harness, and electronic equipment options exist for this popular engine platform. Most swappers adapt the factory electronics to the particular F-Body, but installing aftermarket controllers are certainly an option. If you don’t want to adapt the EFI and drive-by-wire gas pedal technology to your F-Body, then installing a conventional distributor and carburetor on your LS engine is an option. Many wiring harnesses and installation kits are available for LS engines. For my particular project, I adapted the modern LS EFI system.
This tech tip is from the full book, SWAP LS ENGINES INTO CAMAROS & FIREBIRDS: 1967-1981.
For a comprehensive guide on this entire subject you can visit this link: LEARN MORE ABOUT THIS BOOK HERE
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For a first-time engine swapper, buying and installing a complete wiring harness and adapter kit is the best option because creating or modifying a wiring harness and adapting the drive-by-wiring controls is incredibly complex. After all, you want to get the car on the road as soon as possible. Typical kits do not require an incredible amount of electrical acumen; in fact, many can be installed by connecting only four wires.
This is an extra feature on the AAW harness. It allows you to power virtually anything with 12-volt power. Some are key-on-only power and some are full-time power. It really beats having to splice into the main harness as in the old days.
The connector behind the starter tells you what engine you have. The gray one means you have a 58x system; a black connector indicates the older 24x system. Both work equally well to identify which is which for your ECU.
For this complete build, I stripped all the wiring and started over with an American Autowire 18-circuit kit. This kit is specifically made for the first-generation F-Body and it adds blade-style fuses, replacing the old barrel style. It also adds a lot of extra slots for accessories such as a banging stereo or even a power converter.
Although wiring may not be your favorite work, it’s often necessary to complete a project. One option is to pay a professional to do it, and certainly there is no shame in that. The LS engine is pretty straightforward when you can get it with a programmed ECU and matching wiring harness. Beyond that, there are a few common issues when performing this swap.
Gauges
The LS engine is a bit of an oddball when it comes to gauges and locations to put them. But the LS wire bundle is a masterful stroke of genius because you don’t have to wire anything you don’t want to! Since the ECU uses all of the vital parameters that you’d have on the dash to keep the engine running smoothly, you can tap into those systems quite easily using the wiring bundle from the LS harness. Most of these parameters, including RPM, water temperature, oil pressure, voltage, and more, are already coming out of the wiring harness. You need to wire it to the correct corresponding gauge in your gauge cluster. There can be a few exceptions and I cover the ones that you are most likely to need and run into.
The injectors and some of the other connectors have a different way of locking. You need to figure out the type of retention system and clip that needs to be pulled. In this case, the green clip needs to be pulled before the plug can be removed.
I got this Covan’s blank dash from Matt’s Classic Bowties. This allows a platform to custom install the Stack gauge cluster in the stock dash hole without having to custom make a dash panel. The Stack cluster comes with its own template. Make sure you really want this in the place you mark it; you only get one shot at it.
Every great journey starts with one small step and a small hole in the dash panel was mine. I went carefully around the perimeter with a variety of cuttings tools. First I drilled out the corner and then followed the scribe line with a jigsaw. I went slowly so I could precisely follow the scribe line. I also used a pair of shears to get the shape just right.
If everything goes well, this is what you should end up with. You need to install the four buttons near the cluster somewhere. Below the cluster seemed to be as good a place as any for it.
Two straps and a couple of bolts hold the gauge on the back.
Two adapters are an option for most projects. The PN 2277 (top) is the coolant adapter that plugs into the head converting the M12 x 1.5 fitting to allow you to use a 1/8-inch NPT coolant sensor. The oil pressure adapter (P2268, bottom) comes in at M16 x 1.5 and also adapts to the 1/8-inch NPT fitting. (Photo Courtesy Auto Meter)
The American Autowire kit comes with everything you need. It even comes with a new ignition lock cylinder and head light switch. They give you plenty of extra wire so if you take your time, it works out really well.
I know this looks intimidating, but if you go slowly and follow the instructions and wiring diagrams, everything will work.
You need an array of tools and hardware to help you in the wiring process. Some shrink tape, wire cutters, and a wire stripper are required to make the necessary electrical connections and complete your wiring job.
Because I am taking the positive terminal from the trunk I had to bend the terminal to match the bend to the starter.
You need to use heat shrink to end up with a properly wired terminal like this.
My new 18-circuit fuse block bolts right into place without any modifications, so I didn’t have to drill the firewall. The AAW kit is meant to bolt into the stock location, which is a delight. It offers the use of blade-style fuses with larger amperage capabilities and more circuits to work with instead of having to overload the old stock system.
I went through the diagram and located several unused wires, so pulled them from the firewall connector. You need to compress the tabs on the connectors and pull them out of the plug.
This diagram illustrates the correct wiring for a resistor to go inline for your tachometer. The resister needs a 12-volt key-on source to allow it to work properly.
I am pointing at the water plug that can be used for virtually anything to do with the coolant. This hole measures M12 x 1.5. If you’re looking for an adapter, it needs to be this size. Most gauges do not fit this size and need an adapter. Mechanical gauges are usually too big for the adapters, so you have to run an electric gauge or figure something else out. If you’re going this far to put an LS engine in your car, don’t scrimp on the gauges, they are cheap insurance. (Photo Courtesy Auto Meter)
The smaller of the two sending units is the electrical sweep unit. They are solid state, and therefore Auto Meter claims they are less prone to failure from vibrations like its mechanical cousins. The larger unit can be difficult to fit because it takes up more space. In such cases Auto Meter recommends using a piece of braided hose to relocate the unit to a lateral position. This does not have an impact on the reading of the gauge. (Photo Courtesy Auto Meter)
A smaller and shorter water temperature sending unit (PN 2259) is shown. This allows you to save space when mounting on the head. (Photo Courtesy Auto Meter)
Tach Wiring
Tach wiring is fairly straightforward; it is spliced in from the wiring harness and ECU, typically PIN 10 and a white wire (1999 to 2002 have a red connector, 2003 and later have a green connector). In most cases, all that is required beyond the wire hookups is that the tach itself should be set to 4-cylinder or 6-cylinder mode depending on the make and model of your gauge. Sometimes you need to tap the coil wires themselves (usually pink) to run to your tach.
This takes care of most LS tach wiring; however, a few people require a small additional resistor known as a “pull-up” resistor. A wide variance is possible for those who may need to modify the tach signal. You know pretty quickly if you need to do this when you start up the engine and the tach acts erratically or reads inaccurately. Today’s aftermarket tachs require a ground wire as well as a 12-volt source and exciter wire. The exciter wire is the one that can necessitate the “pull-up” resistor.
You need a 5,000-ohm 1/4-watt resistor or a 4,800-ohm 1/4-watt resistor. Often a 680-ohm 1/4-watt resistor works; a best practice is to start with the 5,000-ohm 1/4 version and work your way down. Besides, resistors are cheap and plentiful. You need to run this wire from a fuse-protected keyed (only operates when the key is turned to “on”) 12-volt source and then spliced into the wire from the harness to the tach. Start it up and see if it’s working.
Water Temperature
The LS engine has a variety of ways to measure water temperature. Most notably are the two ports on each cylinder head. On both heads they are at the same location, farthest to the driver’s side of the head. You’ll find a plug that needs an M12 x 1.5 adapter to run an electric gauge. Because the size of the hole, a mechanical gauge doesn’t fit.
Auto Meter has made an adapter for the electric sending unit (PN 2277). This adapter fits right in and has a 1/8-inch NPT port that accepts most sending units. Auto Meter warned me that a smaller sending unit (PN 225) might be needed.
This tech tip is from the full book, SWAP LS ENGINES INTO CAMAROS & FIREBIRDS: 1967-1981.
For a comprehensive guide on this entire subject you can visit this link: LEARN MORE ABOUT THIS BOOK HERE
SHARE THIS ARTICLE: Please feel free to share this article on Facebook, in Forums, or with any Clubs you participate in. You can copy and paste this link to share: https://lsenginediy.com/camaro-firebird-ls-swap-wiring-guide/
The adapter (PN 2277) is installed in the head. I recommend using a thread sealer to prevent leaks and as the aluminum and brass are soft metals. Be careful not to deform the fitting when tightening it. (Photo Courtesy Auto Meter)
The head is already pre-drilled and tapped to accept an electronic sending unit, which is installed in the head. (Photo Courtesy Auto Meter)
I had to use an inline water temperature gauge for the stack unit as the sending units are too large to fit any of the regular places without drilling and tapping a very expensive cylinder head.
The oil filter port is used to adapt the pressure gauge. It is located just above the oil filter on a stock LS engine. (Photo Courtesy Auto Meter)
Just as on the small-block Chevy, the oil pressure port is located at the back of the engine. (Photo Courtesy Auto Meter)
The adapter (PN 2268) was installed on the engine. Be sure to thread the fitting as far in as you can to flatten the washer. Do not over-tighten as these fittings can snap off. (Photo Courtesy Auto Meter)
For my Stack cluster, I wasn’t able to use the larger fitting because the bore was too tight for the sending unit. I thought I could be clever and bore out the fitting, but that ended in failure. I turned to the heater hoses instead. I used an Auto Meter (PN 2280) to help. It’s a 5/8-inch hose adapter that accepts the 1/8-inch port size. I used 5/8 inch because it is the “feed” side of the heater box, meaning that hot engine coolant enters the heater core through this hose and exits out the 3/4-inch hose.
Oil Pressure
The LS engine has an oil pressure plug similar to the small-block in the respect that they are in the same vicinity. That’s about where the similarities stop. This plug requires a special adapter to run 1/8-inch NPT sending units. Auto Meter sells a brass fitting (PN 2268) that allows you to use this pressure port for the cockpit gauge. Auto Meter reports that you can run a short piece of pipe or braided hose from the oil pressure side and it does not diminish any readings you get from the gauge!
Here’s where a few things get tricky. The engine harness needs a port to tell the ECU how much oil pressure is being generated. That typically is the back slot behind the intake in the traditional location. If you use this for your gauge, you have to figure out something else to make the ECU happy,
The solution is a modification to the oil cover plate located right above the oil filter. The oil pan from Mast doesn’t have this option, but I show you how to solve that problem. Drilling and tapping this plate gives you an excellent way to add a gauge without making any unsightly changes. You need to keep everything away from the heat since the headers are directly in front of this piece.
Oil-Pressure Sending Unit Installation
Step 1:
You need to cut off the excess material to make room for the NPT tap, which is tapered. Don’t cut off so much that you have nothing left to thread to. However, you need to remove roughly 1/2 inch to fit the sending unit. (Photo Courtesy Auto Meter)
Step 2:
Use a 5/ 16-inch drill bit to enlarge the center. (Photo Courtesy Auto Meter)
Step 3:
Chase the drilled out section with a 1/8-inch NPT tap. You need to go slow and steady to properly clean metal shards out of the oil filter port. You obviously don’t want metal debris fl owing through your engine. (Photo Courtesy Auto Meter)
Step 4:
You can now screw the oil pressure sending unit into place; snuggly so as not to leak but not too tight to cause a crack.
For my oil pan, I had to be a bit creative. I quickly noticed that the oil pan doesn’t have the typical plate that can be modified. It only has two -10AN ports that are meant for an oil cooler (I mentioned that Mast doesn’t mess around when they build engines, right?). I called Mast and they informed me that the rearward-most port is the “feed” line and provides accurate oil pressure readings. Just as with the stock oil plate, I was able to drill and tap the aluminum -10AN fitting to accept the 1/8-inch NPT sending unit. I added a 90-degree elbow to clear the side of the block to allow the sending unit to clear and not interfere with the hot header. I plan to take the advice from Mast and add an oil cooler.
Oil Temperature
The good news about the oil temperature gauge is that it doesn’t need any pressure; it only needs to be submerged in hot oil to work properly. There are several ways to get the proper oil temperature. You can branch off the oil-pressure sending unit with a T-fitting or you can make its own special slot. Chances are, your wiring harness isn’t using the low-oil-level sending unit. On the passenger’s side of every LS pan is a plug that the stock harness uses for an oil level warning light.
I was able to find the right fitting for my 1/8-inch NPT sending unit. I used a specialty pre-tapped aluminum fitting from Speedway Motors (PN 481201). It allows me to use the sending unit and not make any major modifications. Typical operating temperatures for the LS engine are roughly 195 to 210 degrees F. If you plan to track your car and start seeing temperatures above 275 consistently, you need to add an oil cooler.
I tapped into the right side of the Mast oil pan to access the pressure side to get an oil pressure reading.
After drilling and tapping the appropriate 1/8-inch NPT hole, I reattached the oil pressure–sending unit.
This is a Speedway Engines adapter (PN L-0201). The oil pan temperature replacement plug allows you to have a port for the oil temperature with a 1/8-inch NPT tapped port.
You might have to remove the sensor to get the fitting in. Remember to use a little Teflon tape to seal any air leaks. Thread it into the head by hand until it is snug.
The brown port behind the starter is the oil level sensor. Removing it with a socket or wrench allows the adapter to monitor the oil temperature.
Fuel Pressure
You must maintain the correct fuel pressure of 58 psi at all times in an LS engine to realize maximum performance. I used an -8AN adapter from Earl’s that allows me to run a 1/8-inch NPT solid-state sending unit that matches the stack EFI injection stack unit (PN AT100196ERL).
To check the fuel pressure, insert the key into the ignition and turn it to “on” so the EFI system primes itself. It should turn the fuel pump on for 2 to 5 seconds and shut off if the car is not running. This allows you to check the gauge and fuel system leaks.
Wiring Harnesses
A number of automotive businesses, including Painless Wiring and American Autowire are more than happy to build a wiring harness for you. It will be more costly, but it’s an option if you don’t have a lot of time. You can, of course, build your own wiring harness as I have shown you.
Both companies make great kits to suit any need and in many cases make kits that far supersede anything that came from the factory on the first- or second-generation F-Bodies. I chose the American Autowire kit because I’ve had experience working with their systems and felt comfortable using them again. The best advice I can give you is to go slowly! Take your time and work with the components one at a time. It can be a bit daunting when you see all the wires in one giant bundle, but if you look at each circuit individually the bigger picture tends to take shape.
You need to know a few things up front before you order a harness: the transmission needs, whether you are sending a harness to be reworked or purchasing one, the length of extra harness (crucial if you want extra to mount the PCM under the dash), the oxygen sensor requirements, and the fuse/relay box needs.
You can use a wiring harness from a junkyard or you can have one made out of whole cloth but you should be prepared for some extra cost.
Fabricators usually ask questions about your particular build. You need to determine which computer you are going to use and specify which transmission will be installed. If it’s an automatic, you need to program the ECM’s shift points and transmission functions or you’ll have to use an external stock ECM or aftermarket version. You also need to determine if you are going to be running A/C. In addition, you need to decide whether to use a speed-density system or a mass air system.
The final consideration is the length of your harness. To figure that out, you need to decide on the mounting location of the computer because that dictates the length of the harness. You can mount the ECM in the passenger’s compartment and run the wires through the firewall. If you choose this placement, you need a longer harness than if you mount the ECM in the engine compartment.
Wiring Harness Installation
Step 1:
The Mast wiring harness comes pre-labeled with many of the popular connectors already marked. It’s nice when things are so easy. Since the Mast harness is customized and pre-routed for the particular engine, connecting the wires is a no-brainer. Decisions about the fuse box and ECM are crucial. Those need to be free from heat, free from vibrations, and in an easy-to-access area.
Step 2:
Here’s the Mast wiring harness that came with the engine. Everything is well laid out and fits to the block (doing its best to remain hidden).
Step 3:
The M-90 DBW ECU from Mast is a pretty solid piece. It comes with rubber grommets. It’s up to you to find a good place for it away from vibrations, heat, and excess moisture.
Step 4:
This is the original gas pedal; it has to go. The drive-by-wire pedal will be mounted to the firewall.
Step 5:
This jumble of wires is not as confusing as it looks. Everything has a place and there is a place for everything. Go slowly and it will make sense very quickly. Because each wire has only one way to be routed and only one specific counterpart to be plugged into, routing/connecting the wires is a simple procedure. After it’s clicked into place, tuck the wire behind anything close, such as the injector.
Step 6:
The American Autowire (AAW) kit replaces the old front body harness further along in the build.
Step 7:
Removing the old wiring harness can be difficult but if done carefully I can probably resell it at the swap meet and maybe recoup some of the cost. Many of the wires from the factory are held in with bent tabs or clamps. It pays to follow each wire cluster until you get to a junction then gently remove it.
Step 8:
Here are the original gas pedal (left) and the new DBW gas pedal (right) side by side.
Step 9:
Once all the wiring has been removed, you can start to plan your wiring setup more carefully.
Step 10:
Here’s everything you get in the AAW wiring kit: a new ignition switch, bright beam switch, and headlight switch.
Step 11:
The idle air temperature sensor is an easily missed connection. This one just plugs 10 directly into the K&N air filter.
Step 12:
The Mast harness comes with three connectors under the dash in addition to the main wire bundle. They are: OBD-II port (upper right), drive-by-wire port (right), and ECU interface (left). Determine the location in the foot well to mount it, drill two pilot holes, and then screw the plug down with sheet-metal screws. Your wiring harness most likely only has the OBD-II port and drive-by-wire plug.
Step 13:
To get all these wires in the dash, I had to cut a 3-inch access hole in the firewall. I use a 3-inch rubber grommet to make sure air and gases don’t enter the cab. Placement of the hole depends largely on what you want to do. If you want a hole closest to the gauges for ease of wiring such as I did, this is a good location. Others have put a hole behind the engine to hide the harness. The choice is up to you.
Step 14:
This is the bundle that comes out of the Mast wiring harness. Most of these wires aren’t necessary for the entire wiring. Some go to gauges while others are crucial, such as ignition and key-on cycling. Wires that are not used are capped. It helps to have the wiring diagram handy to make sense of it all because each wiring harness is slightly different. This harness came with a set of instructions. I pulled back a good part of the sheathing to reveal the wire markings to determine which was which.
Step 15:
A ground strap can be found at any local auto parts stores, and you need to be sure your electrical system is properly grounded. Because this frame was powder coated I had to scrape some off to make sure the ground strap had excellent metal-to-metal contact.
This tech tip is from the full book, SWAP LS ENGINES INTO CAMAROS & FIREBIRDS: 1967-1981.
For a comprehensive guide on this entire subject you can visit this link: LEARN MORE ABOUT THIS BOOK HERE
SHARE THIS ARTICLE: Please feel free to share this article on Facebook, in Forums, or with any Clubs you participate in. You can copy and paste this link to share: https://lsenginediy.com/camaro-firebird-ls-swap-wiring-guide/
Wiring Harness Hookup
Don’t let this giant bundle of wires intimidate you. I like to call this type of automotive work a “process of elimination.” Once the engine arrived at my place, I promptly removed the wiring harness and started working on the engine accessories and other pieces. After a while, the harness had to go back on and I couldn’t remember the right way to install it. Thankfully, the weather pack plugs and configuration allowed me to figure it out quickly. It’s pretty hard to mess this up when everything has a specific place and corresponding connector. If you organize them, everything should go smoothly.
Chances are that your wiring harness is original and looks a lot like mine. While it’s entirely possible to put an LS engine in your car and get it working well, installing an updated kit, such as the AAW kit, can make life a lot easier.
To remove the original gas pedal, remove the two bolts holding the pivot arm in place. A simple socket does the job even though it can be a bit of a pain and the plastic holder can easily break. Remove the cable from the pedal and it should fall right out after removing the bolts located on the firewall that hold the pedal lever in place.
Length of Harness
Any wiring harness company worth anything asks you how much “extra” length you want in your harness. The extra length allows you to mount the ECM and the fuse block in a suitable location. The location determines how much extra length you need. I’ve seen extra lengths range from ultra-short (where the components are mounted in the engine bay), to super-long, as in 3 feet or longer (to accommodate mounting inside the passenger compartment). This extra bit determines where you can put your ECM in the vehicle. It might be worth figuring out where you want to put your computer well before you order a harness.
OBD-II Port Location
Any wiring harness should come with an OBD-II port. This is a standard port for all newer vehicles. It allows you to plug in a scan tool or laptop to “talk” with the PCM to program it further or troubleshoot codes that are being thrown.
The wiring harness side is a female 16-pin J1962-type connector with two rows of 8 pins. The government standards mandate that this must be within 2 feet of the driver’s position. This is the best position because it allows you to use the scan tool or laptop while in the driver’s seat to turn the car on or off with the key.
I located it under the dash within easy reach and away from the pedals. Of course you can position it anywhere you like. People who want the clean look put it in the glove box.
Written by Eric McClellan and Posted with Permission of CarTech Books
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