The LS engine as we currently know it was introduced more than twenty years ago. Let that sink in. When they first came out in the new-at-the-time C5-generation Corvette, they were a totally new design, and not many folks outside of Chevrolet knew what to make of it. Sure, it had 345 horsepower – more than its predecessors – but being drawn from a clean sheet of paper, there was little besides its bore centers and the term “small-block” that linked it to previous powerplants.


The power and fuel efficiency of the LS-based engines is a result of EFI and other techniques. Your vintage car can also benefit from their design.

History seems to be repeating itself with the new “small-block Chevy” becoming the go-to engine for those wanting more, and for good reason. Horsepower has increased to 650 ponies in factory trim, and the sky is the limit if you’re looking to build your own. Plus, one of the major hurdles in bringing one of these newer-gen small-blocks to life has been addressed, and enthusiasts have options from both the aftermarket and the General himself.

Interfacing with your LS engine can be done via a small, hand-held display or through a laptop.

Whereas the lack of a distributor and an Octuplet of coils mounted on the valve covers originally made many enthusiasts scratch their heads, time has shown that the early adopters were right, and there are benefits to be had in this new engine configuration.

Many of the early swaps were powered by the OEM computer. This made perfect sense, since those ECUs were already designed to make use of new technologies used on the Gen III engines. Items like drive-by-wire throttle, Active Fuel Management (displacement-on-demand), and cam phasing on later offerings were all factory tricks to get the most power for the least amount of fuel and emissions.


Your LS will need a harness, even if you choose to use a carburetor. Make sure your harness has all the capability that you’re wanting from your engine. It’s easier to purchase the right harness than to remove it and update it.

While many of the aftermarket ECUs have adopted drive-by-wire capability, if you’re looking to utilize any of the cam-phasing or AFM benefits, or are using any of the Gen V (direct-injected) LT-based engines, then you’ll want to stay pretty close to the OEM when choosing an ECU. If you’re looking at modifying an earlier version (Gen III or Gen IV), then the aftermarket is lining up, waiting to speak with you. There are two things that you need to ask yourself, and finding the right ECU for your application hinges upon answering these two questions properly.

Knowing What You Have
While that sounds like a simple question, it’s actually pretty important. You see, while the Gen  III, Gen IV, and even the Gen V engines may look similar when torn down to their base materials, there are some differences that you’ll need to know before you can make any computer work properly with them.

Here is a three-bolt camshaft gear from a 1997-2004 LS1, LS6, or other Gen III V8. (Note no reluctor teeth since the camshaft position sensor is at the back of the block). Next is a three-bolt 1X camshaft gear from a 2005 LS2 Corvette or 2005-2006 LS2 GTO/SSR/Trailblazer. GM then went to a three-bolt 4X camshaft gear in the 2006 LS2 Corvette and 2006-2009 LS7 Corvette, and then back to a single-bolt 4X camshaft gear from the 2007-2009 LS2 and LS3 (third photo). Images:

One of the benefits that both the Gen III and Gen IV engines offer is a fuel-sipping sequential fueling strategy, which injects fuel to only the individual cylinder and at just the instant that requires it, according to the firing order. Since the piston has two TDC events – but only one firing event per cycle – the ECU needs to know where the engine is in this cycle. Since the position of the camshaft dictates this timing, a camshaft position sensor is used to share this information with the ECU.

The preferable approach is to use a custom, aftermarket harness that eliminates needlessly long wire runs. This eliminates the problems that are often associated with an OE harness that may not have been “gently” removed from the host vehicle. – Dave Emanuel, Digital EFI

The confusion arises because the Gen III and Gen IV used gears with different numbers of teeth to help the ECU determine the proper timing. Gen III engines have a 24x wheel for the crankshaft sensor and have the camshaft sensor located in the block at the rear of the intake manifold.

The Gen IV engines have the sensor in the front cover, reading the front of the camshaft gear. The Gen IV engines use a 58-tooth wheel for the crankshaft position sensor. Besides sensor location, the number of bolts that hold the cam gear in place changed over the years. Knowing the configuration you have, is key to getting your engine up and running properly, no matter what computer you use.

Know What You Want

Knowing what you want from the beginning could make the difference between satisfaction, or re-doing parts of the project as your search for horsepower continues. Changes are rampant throughout the Gen III and Gen IV production runs. Some are beneficial and make upgrading your ride with LS power simpler, but they could require a change if you dare to push the envelope further.

The LS platform does not have provision for a mechanical fuel pump, so you’ll need a way to control the amount of fuel your engine receives from the tank. OEM and aftermarket ECUs both have provisions for driving electric fuel pumps. Since the LS engines came with both “return” (pre-’99) and “returnless” (’99-present) fuel systems, and depending on what type you are using, you’ll need to have a means of properly controlling the pump for each system, whether constant powered or Pulse-Width-Modulated (PWM).


Whether aftermarket or OEM, make sure that your harness supports whatever features you’re wanting (DBW, nitrous, and/or boost controllers). Many aftermarket harnesses come with relays and fuse boxes. Even the leads on this unit from EFI Source come labeled where they should go.

Likewise, if you’re planning on including any power adders down the road, you will want to consider this when shopping for an ECU. Many aftermarket units have provisions for boost and nitrous control, as well as fuel and timing requirements for each. The OEM computer can be made to work within reason for each, but you’ll be buying a tuner, paying someone to configure the tune or looking at some external aftermarket solutions.

Another benefit of some ECUs is data logging. This feature can be highly beneficial when chasing down an issue or doing some fine tuning. If you are looking for plug-and-play, this feature may not be of value to you, but knowing that going in could save you some frustration.

From The Factory

Let’s face it, the factory ECU is quite capable of controlling a bunch of horsepower and providing great fuel mileage while doing it. It has a lot to offer! Even if everything swaps over from the take-out vehicle to your vintage ride, you will still need to make some changes. That will require a program like EFILive, even if you’re not tuning for more power.


Image: MRK

Computers are constantly evolving, and the computer in your car is no different. Dave Emanuel helped us understand some of the differences between various production years and what to look for if shopping for an OEM computer for your LS swap.

The ECM (or PCM) of choice depends on the original equipment configuration. With Gen III engines, which have a 24-tooth reluctor on the crankshaft, a “411” PCM is the standard for 2000 and later-year models. The caveat here is that through 2002, both cable and electronic throttle control was available, so the PCM has to be properly configured to match the throttle type. The 1997-98 engines use an entirely different PCM, and although the 1999 PCM is of the same type as the 2000 and later, some pin-outs are different.

With Gen IV engines, which have 58-tooth reluctors, it’s best to stick with the same type of controller as used originally, either E40, E38, E67, E78 or E92. You can find specifics as to year and model for each controller on the EFILive website by clicking here.

Changing controller type shouldn’t be a major problem, provided the sensors and controllers on the engine are compatible. E38 and E67 controllers are similar, although the E38 has two harness connectors and the E67 has three. Also note that the E38, E67, E78, and E92 were also used on engine platforms other than V8.

We asked Dave Emanuel, president of Digital EFI, a U.S. distributor of New Zealand-based EFILive’s products, about successfully swapping LS engines into a vintage ride. “All LS-based original equipment engines are designed to operate in conjunction with electronic engine controls. As such, an ECM or PCM (in the case of Gen III engines) is required. So is a harness to connect the control module to the engine sensors and controllers. The preferable approach is to use a custom aftermarket harness. Doing this eliminates needlessly long wire runs, and also eliminates the problems that are often associated with an OE harness that may not have been ‘gently’ removed from the host vehicle. In any case, an OBD2 connector is necessary, not only for programming, but for reading and resetting trouble codes.”

EFILive can program all relevant ECMs through the 2017 model year. Some people like to shut off the Displacement on Demand/Active Fuel Management function, and camshaft phasing can also be altered or shut off. Turning off VATS (Vehicle Anti-Theft System) is basically a requirement with a swap, because the new vehicle probably doesn’t have the matching hardware. Also, you’ll likely need to turn off any rear oxygen sensor and catalyst efficiency codes depending on the vehicle’s configuration.

If that sounds like more than you want to take on, the aftermarket is ripe with offerings to put an LS under your hood. While the various offerings are great for enthusiasts, knowing which one is best for you requires some research. By having a plan, you can check that a particular unit fits your needs. Running drive-by-wire? Want to run a carburetor? How about nitrous or boost? Speed Density or MAF? There are a lot of options! We did some scouring to find differing ways to make your LS run. Here are a few aftermarket options you’ll want to consider.

High Carb Options

Some folks still want to run a carburetor on an LS-based engine, and the aftermarket has you covered. While you can likely get away with a low-pressure fuel system if you’re using a carburetor, you’ll still need an electric fuel pump somewhere, and a means for operating the ignition.

Transmission controllers like these from EFI Source (Left) and Baumann Electronic Controls (Right) will get you running through the gears.

MSD has a handy LS Ignition Control Module that will handle all aspects of your LS engine’s ignition. It can be installed on both 24x and 58x crankshaft trigger engines, and features several ignition features. There are six preprogrammed timing tables that are changable with a rotary selector switch for easy timing changes. The module has data acquisition, and is nitrous and boost compatible. It also contains max and launch rev limiters.


MSD makes this handy ignition module that allows you to run an LS engine without an ECU.

If you’re using a carburetor with an electronic transmission like a 4L60E or 4L80E, Baumann Electronic Controls offers a throttle position sensor (TPS) that allows your transmission to know your intentions. They are available for Edelbrock and Holley carburetors.

Injected Options

There are various choices for running EFI on your LS engine, ranging from bare bones operation to high-optioned controllers that have numerous input and outputs for the ability to control all aspects of your engine. Some are self-contained, while others require separate modules to make everything work or to expand their capability. Most LS-based engines are drive by wire, but if you are looking to run a throttle cable, Lokar has a handy bracket (PN TCB-40LS1). Early LS1 intakes have the bosses but didn’t have the M6-1.0 threaded inserts necessary to bolt the throttle bracket to the intake. They can be ordered through Grainger (PN 4ZU28) and install easily.

Interacting with the ECU can be done in various ways, depending on the style and brand of computer you are using.

If you’re looking for plug and play, EFI Source has a controller using their MicroSquirt ECU. In their own words, “This is the ultimate “bare bones” Plug-and-Play package for those who only need to control fuel and timing.” They also offer their MS3 LSX Plug-and-Play Gold Box. This brings options such as boost control, camshaft-phasing, traction control, and others to the install, as well as a much broader tuning range.

A "complete" system might mean all of the necessary wiring, ECU and sensors, as in this MS3 "Gold Box" by EFI Or it could be a complete engine/transmission combo with the ECU and all necessary hardware like this Connect & Cruise LS376/480 package available from Chevrolet Performance.

Fuel Air Spark Technology also offers controllers for LS swaps. The user-tunable FAST XFI 2.0 controller carries all of the usual functions for LS operation as well as fuel pump and cooling fan controls. It includes a FAST XFI 2.0 system, an XIM Ignition Module, and all necessary plug-and-play wiring. If you need to control an E-transmission, you can also link the XFI 2.0 to the optional FAST EZ TCU controller. Their plug and play EZ-ECU kit self-tunes once all the pertinent information is installed via the touch-screen.


FAST offers their XFI 2.0 system (user tunable) or their EZ-EFI (self-tuning) system for those who want more plug and play.

Another major player in the LS controller arena, Holley offers several EFI controllers for LS applications. Their Terminator series includes everything you need to control your stock or mild-modified LS engine. It comes precalibrated for no-hassle installation and tuning, and is adjustable via the included 3.5-inch color touchscreen. Their HP series is tunable via laptop, and like their Dominator ECU, carries a broad range of options to suit even the most hardcore power junkie. The Dominator ECU has more input and outputs, and allows control of an E-transmission whereas the HP does not.

Holley offers their plug-and-play "Terminator" ECU, as well as their "Dominator" and "HP" series of computers. The Dominator and HP are both user-tunable.

When it comes to swapping in an LS powerplant, popularity is definitely a plus. With the numbers of engines available as take-outs, and aftermarket options increasing daily, it’s becoming much easier to enjoy all the benefits that a late-model engine brings to the under-hood area of your ride. In fact, you can check out another article that showcases a lot of the actual install parts you’ll need by clicking here. If you’ve already made the switch to LS power, feel free to let us know in the comments below!