Article by: Shawn Henderson, retrolsx.com

In the world of drag racing, LS engines have been making a big splash since they first showed up in the burnout boxes in 1997. They offer a great platform to build engines whether you are running 8s, or 12s. We decided to come up with the basics on what it takes to swap an LS engine into an older vehicle not originally designed to accept it. Most of these have to be done for those running higher end classes, but we wanted to make sure we covered it all.

The Engine: Where To Begin

The first question to ask yourself is where can I find the drivetrain? You have a few options here, all with their own pros and cons. Let’s take a look at those options to determine which one best suits your needs.

Option #1: Factory Crate Engine

A quick call to any local or online GM dealer such as SDparts can offer any factory crate engine delivered to your door at the click of a button. GM Performance Parts also offers a number of engines available in short, long, or complete engines.

Also available is the new GM Performance Parts E-Rod Package. These factory crate engines mirror the engines they are centered around, but they also include everything you need to operate the engine including the computer, wiring harness, and emission devices. Now before you laugh at the last item on that list, remember that this kit is the only engine package that is CARB certified to be installed into any emissions controlled vehicle, even if you live in the Golden State.


Options like this LS3 can be ordered right from your favorite GMPP dealer.

Option #2: High Performance Crate Engine

If a hand built crate engine with options from 400 HP to over 800 HP that uses pump gas is more your style, then the gurus at Mast Motorsports have got you covered. Mast has developed the only VVT (variable valve timing) retrofit harness and can even custom tailor any crate engine for retrofit application using OEM or aftermarket components. Seriously, these guys are no joke when it comes to making ready-to-run monster LS power.


Mast line of VVT engines are the the first to run GMs new VVT in performance application.

Option #3: Used OE Engine

The third and most popular option is an engine from a totaled car. When a brand new engine is out of the budget, a low mile donor motor can be sourced locally from Car-Part, salvage yards, or even eBay! These pullouts offer complete engines, transmissions, front accessories, and OEM wiring harnesses with ECU at a fraction of the cost of new.

The pullouts from the ’99+ GM trucks offer the best bang for the buck which can be bought for around $1,000 for a low mile 2wd 5.3L/4L60 combo. With this set up, don’t think for a second that these low cost engines can’t shred a tire. My own personal 5.3L laid down an impressive 330 RWHP and 326RWTQ!

The Engine: Making It All Fit

So let’s say that you now have the engine. The question now becomes how to go about fitting the engine into a vehicle that wasn’t originally designed to accept it. The solution is easy, but not as easy as just buying some new motor mounts. Let’s start from the engine and work our way out to determine what other components are necessary in our swap.

Drive Systems

Currently, there are three different versions of front accessories drives from GM: the F-Body and GTO system, the Corvette and CTS-V system, and the truck, SUV, and SSR system. The car and Corvette systems are both tucked up close to the block and will fit in most conversions. Unfortunately, the truck’s bulkier design limits its fitment in applications.

Any GM accessories can be modified to fit using GM or aftermarket components. On the truck accessories, a compact ’98-’02 Camaro alternator offers extra hood clearance. The aftermarket offers a high output alternator from PowerMaster. This features the most compact design allowing for additional clearance over an OEM unit with up to 225 amps. These guys also offer a stronger starter that helps crank up those big cube LSX engines.


The compact alternators can help fit the truck accessories, while the starter can turn over any engine even the monster LSX.

A large power steering gear box can contact the truck power steering pulley, therefore a smaller pulley from a mid ’90s S10 4.3 can be an easy press on fix. The low mount A/C compressor can contact the frame on all GM accessories in a few swaps. This can be a quick bolt on fix with the top mount A/C kit from Kwik Performance. This bracket kit for under $200 mounts the Sanden 508 A/C compressors that are tucked up in front of the passenger’s side head.


These KWIK brackets can help adapt any LS car or truck engine accessories to a more compact design.

A Sanden 508 compressor is the standard unit for most aftermarket A/C kits including Vintage Air. Vintage Air offers numerous A/C kits for just about everything with four wheels. These kits must be ordered specifically for LS platforms due to belt design.


Vintage air offers one of the most complete line of retrofit A/C components.

In addition to the A/C kits, a complete front accessory drive system with A/C called the Front Runner kit is available from Vintage Air. The Front Runner was developed to give maximum clearance in the engine bay making installation easier while pairing it with a show finish.


Billet Specialties also offers a great front drive system called the Tru-Track System. It uses the top mount A/C Condenser as well.


Here the LH8 oil pan also know as the Muscle Car oil pan from GMPP. It’s a low cost pan but its 7.5IN depth can make it a ground scraper in certain swaps.

Oil Pan

These are definitely required for the swap. Each vehicle platform requires a specific oil pan depending on the vehicle’s unique frame design. Currently, several aftermarket oil pan options exist from Milodon, Canton, and GMPP. The aftermarket options include increased oil capacity and better ground clearance over most OEM units. The Milodon unit holds 7 quarts of oil with a tucked up 6in low spot that allows for excellent ground clearance with a remote oil filter.


Milodon answer for LS swaps, offers a compact rear sump for most vehicles.

The Canton units are available in aluminum or steel versions with a screw on or remote style oil filter adapter.

Don’t count out GM’s cast units ether. GM has a wide range of production options that are designed to add block rigiditydue to thick 3/8 flanges. But what I suggest looking for is the GMPP Muscle Car Oil Pan. This pan is designed to make LS swaps easy with plenty of ground and subframe clearance.



Engine Mounting – The DIY Way

Now that we have our engine and other necessary components for our swap, how the heck do I make this engine fit into my car? To start off, the LS series engines share no mounting characteristic of older small block Chevys. All LS engines feature a new bolt pattern for the motor mount and require adapter kits to retrofit these in older applications.

There are really two ways to go about installing your new LS engine to the vehicle of your choosing. You can source all the necessary parts yourself or buy a kit that includes everything you need to make the swap happen.

The aftermarket has several choices that range from adapter plates to complete conversion kits that are specially engineered for each application. Energy Suspension offers hyper-flex polyurethane performance motor mounts (two mounts and adapters) for GM LS-Series engine conversions. These mounts are drilled plates that allow for a polyurethane SBC motor mount to be bolted to the LS engine.


Energy Suspension now offers plated that include their high quality polyurethane bushing.

These plates differ in the offset between manufacturers. It is highly recommended that all parts be bought with their corresponding parts in order to prevent mixing and matching headaches. Be sure to check the requirements of each kit. Different versions can require aftermarket oil pans, certain front engine accessories, and custom crossmemebers to clear with headers. To ease the installation process, it is recommended that you purchase your conversion kit and headers from the same retailer.

If you go with a kit that does not include headers, then you are going to need to purchase some. Kooks Custom Headers offers their retrofit header kits in a 304 stainless steel with a flow spike for added performance. Kooks conveniently offers a 1 7/8 header with LS adapter plate for two early GM applications and even the Fox Body Mustang!


This photo is of early pre-production Kooks headers, production will be in the Kooks standard 304 stainless steel.

Engine Mounting – Swap Kits

Edlebrock is expanding their LS swap product line with header kits that are offered in a 1 ¾ stepped to 1 7/8 for the 64-72 A-Body that includes recommended LS swap plates. Currently, the Edelbrock system is the only full exhaust system available for any LS conversion.


Edelbrock offers one of the most complete kits for the A-Body with full exhaust kits.

Another option is BRP Hot Rods LSX swap kits that include all the necessary components to mount the LSX engine and modern transmissions using the GM accessories and oil pans. BRP offers these conversion kits for 1955-1998 GM cars and trucks. Most feature bolt in polyurethane frame mounts for simple installation with a matching crossmember designed to clear up to a 3 ½ inch exhaust.


These are 1 ¾ headers and a 1967-1969 Camaro kit.

For each conversion kit, BRP offers seven corresponding versions of Muscle Rod hedders by Husler from Hedman. (Any header manufactured the by the Hedman group is consider a “hedder”.) These hedders range from a 1 ¾ inch mid length to a massive 2 inch long tube hedder with up to a 3 ½ inch collector.


1964-1967 A-Body and a mid length hedder.

When purchasing a conversion kit, be sure to get the corresponding parts such as an oil pan, headers, and front accessories. Also, more and more companies are adding LS Swap kits everyday, so keep an open mind as to who you use.

Fuel System & Intake

After the LS engine is in the car the next big question is whether to go EFI or Carb. EFI takes a little more effort, but the payoff is huge! Overall, the cost is about the same either route you take. However, the fuel mileage, reliability, and peace of mind that comes with EFI is well worth the extra work and time involved. The horror stories of tangled wires and abandoned EFI conversions that once scared away most enthusiasts are a thing of the past, so don’t let that fear stop you.

The first harness needed would be for the LS engine that’s being installed. This harness is a standalone Electronic Computer Unit (ECU) and wiring harness. It’s this harness that will control and monitor the new drivetrain in any older vehicle.

The first option is a new wiring harness from a company such as Painless Performance. Painless offers several harnesses for nearly any application from the early cable driven units to flex fuel harness that are currently under development. This out of the box harness offers direct hook up with the OEM connectors. Painless recently started offering a complete body harness with LS provisions and body harness.


These are some complete harness options from painless that make for a straightforward install.

Your local GM dealer also offers an over the counter drive-by-wire ECU harness for GEN IV engines from GMPP called the LS Controller. This harness is everything you need from the wires and sensor to the computer and pedal necessary for the drive-by-wire system to operate.

When using donor motors, you can contact a company such as Current Performance and send off the OEM harness. Current Performance will rewire and reprogram the OEM harness and ECU as a low cost high quality alternative.

The second option available is the body harness. This controls the other functions of the vehicle such as the lighting, gauges, windows, radio, accessories, etc. If the original vehicle harness is beyond saving, American Autowire can help. American Autowire kits work with almost any modified OEM, stand alone, or aftermarket fuel injection harness. They manufacture complete vehicle-specific Classic Update kits for a wide range of classic GM car and truck applications.

The next step is upgrading the fuel system to handle the higher line pressure and baffling the tank for EFI engines. An EFI fuel tank is highly recommended to control fuel slosh and engine starvation under hard cornering or low fuel. EFI fuel tanks can be bought from Rock Auto, and they are shipped with the tank and GM fuel pump for under $500. Since Rock Auto does not carry every type of fuel tank, Rock Valley can modify the existing or replacement fuel tank for any car for around $500 including labor and parts. Rock Valley also offers complete stainless steel units with fuel pumps options for a show quality set up.


Rock Valley offers custom built or modified tank for any swap.

After the EFI fuel tank is installed, a fuel regulator is required to get the 58 pounds of line pressure that’s required for the EFI system to function properly. As far as regulators go, there are endless options available from nearly every performance catalog on earth. The GM option is to order a 1999 C5 Corvette fuel filter regulator (GM PN 10299146) from any local auto parts retailer. This regulator hooks the supply and the return line to the rear and runs only the single supply line to the car intake.

A regulator is only required on the car style intakes. The truck style intakes have a fuel regulator built into the intake. The truck style only requires a generic fuel filter on the supply line, but it requires both the supply and return line to be directly connected to the truck intake.

If you prefer the classic look of a carb, simply bolt on a traditional intake on the LS engine and crank it up in a weekend. Several versions exist from both GMPP and Edlebrock for all performance needs. Both intake manufacturers recommend the MSD style controller box to run the coil packs.


This is the GMPP Intake we used on our 454 LS for Project All Air.


Edelbrock has every style of fuel delivery option covered. You can even throw a pair of dual quads on a LS1 now!

The third option is to dump the coil packs all together. This is possible with all of the off the shelf GM parts using the front drive distributor kit that runs a traditional distributor on the front of the block for an old school look. (PN 88958679 requires a Ford distributor and a mechanical or low pressure electric fuel pump PN 6472657).

Transmission Side Notes

Regardless of how the spark is controlled, a control module is required for a modern electric overdrive transmission (GM PN 12497316.) One side note when running a T-56 or 4L80+, some trans tunnel stretching may be required and a drive shaft needs to be modified to fit with the new location of the tail shaft.


Here the two most common automatic tail shafts can be compared. Note the different transmission bushing mounting points.

Muscle Car Overdrive can custom make any driveshaft from steel, aluminum, or even carbon fiber depending on your budget! Muscle Car Overdrive also has a full line of performance transmissions in all horsepower ranges in just about every model imaginable.


With Muscle Car Overdrive any transmission combo is offered with steel, aluminum and even carbon driveshafts.

When running a carb, a manual or a non electronic transmission is recommended for easy install due to the limited electronics. When adapting an older transmission, a crankshaft spacer (PN 12563532) is required as well as longer bolts (PN 12553332) in order to attach the flywheel. It’s a direct bolt on for hard mounting the transmission onto any LS engine. Another great product is the McLeod hydraulic line kit for older transmissions. This feature can be a life saver for LS swap headers that were developed using modern hydraulic T-56 units over the Z-bar.

The Vehicle: Cooling System

The cooling system flows in a traditional way on the LS engine, unlike the LT1 Gen II engines. Any older heavy duty radiator or aftermarket LS specific swap radiator can be installed with recommended high performance electric fans. The common trick is to install OEM units from newer cars. Some great options are the ’98-’02 F-Body twin electric fans or even the mid ’90s Taurus 3.8 electric fan if you’re on a budget. All versions can be bought second hand and are easy to install in most applications. Flex-A-Lite offers aftermarket electric fans in countless variations for every vehicle on the road.

Another unique feature on the LS engine is a steam vent which purges air from the engine and feeds the throttle body with coolant which must be connected into the cooling system. Be Cool designed a plug for this requirement into their LS radiators. Be Cool’s line of LS radiators also offer interchangeable hose outlets on the radiator for the various waterpump outlets for trucks, Corvettes, or cars. This exclusive design makes running the hoses a breeze.


Be Cool offers some of the best radiators in the industry and have LS specific option with cross flow cooling for maximum performance.

Keep in mind that another option is to drill and tap into a water pump for the steam vent. You could also use couplers in between the radiator hoses for an easy hook up. When it comes to finding radiator hoses, a clever suggestion is to bend a coat hanger into the shape needed then head to the local auto parts store to find the perfect fit.

The Vehicle: Gauges and Other Electronics

After the engine is in the car and the cooling system is installed, the next step is to hook up the gauges. The easiest way to achieve this is to run a Dakota Digital or Classic Dash Gauge cluster. Classic Dash offers twenty-two different styles of gauges for every gauge cluster with carbon fiber, brushed aluminum, or classic black dash finishes.


Classic Dash offers complete dash replacements with several gauge designs packages.


The Dakota Digital units use a digital read out and replace the whole cluster with an easy to program dash that will also record data on the vehicle’s performance.


If digital units aren’t in the budget, the OEM gauges can be modified to work with a couple of adapter parts.

The first gauge to consider is the speedometer. Modern GM transmissions use an electron signal (VSS) to determine the speed. Option one is to run a SW Fabrications modified tail shaft with a gear drive built in. The SW fabrication kit includes an adapter bracket to bolt on a traditional four bolt 4L60 tail shaft. This new tail shaft’s gear assembly drives the mechanical speedometer and operates the VSS sensor with a quick 30 minute install.


The tail shafts adapter mounts a older mechanical 4 bolt 4L60 housing for a tradition speedometer cable.

A second option is to connect an Abbott Tach Cable-X Box that converts the electronic signal to a gear driven cable. The Cable-X Box is easy to install and hooks up with only a few wires. One nice feature of the Cable-X Box is that it’s tunable, so if the tire and rear gear ratio changes the box can simply be reprogrammed.


The Abbots is simple solution for the VVS speedometer outfit. This box will convert the electric readout into a gear driven output.

The next gauge to consider is the tachometer. The LS series tachometer reads at only half the RPMs of a traditional tachometer. The readout is easily converted by setting the tachometer for a 4 cylinder readout (2 PPR). This bit of advice may seem strange given that the LS engine is a V8, however, the factory tachometer signal output is only a true 4 cylinder signal (2 PPR). Abbots, the makers of the Cable-X Box, also offer adapters for mechanical linkage tachometers as well. The temp gauge is connected by removing the bolt on the rear of the passenger’s side head and installing a mechanical sending unit in its place.


The hole size, once removed, is 12mm x 1.5. There are three types of gauges to keep in mind. First, there is the short sweep electric which uses a 1-wire sender. Secondly, there is the full sweep electric which uses a 2-wire sender. Finally, there is the mechanical which has a permanent capillary tube.


The passenger side heads is the most common area tapped for a coolant sensor. Shown is the adapter fitting used need to convert it to 12mm.

The oil pressure line is tapped into the oil bypass plate above the oil filter by drilling and taping it for a mechanical oil pressure sending unit. This is the small two bolt plate that is above the filter. These differ between production models, but all will require similar modifications.

Mark the location that is optimal for your sender or fittings. All Auto Meter oil pressure senders and electric oil temperature senders are 1/8”NPT, including mechanical oil pressure fittings. Remove the cover plate, and be sure to save the bolts & gasket as you will re-use those later on. Use a center punch in your marked location, then drill with a 5/16” drill bit. Next, follow through with a 1/8”NPT pipe tap. Blow the shavings out, and re-install using the same gasket and bolts. You now have a hole for oil pressure or oil temperature.


This little guy is the oil pressure sensor on a modified LS1 oil bypass plug.

Once the gauges are hooked up the swaps pretty much wrapped up and the car should be ready for on road testing. While this covers only the general parts needed for a swap, this is only a basic swap article to familiarize the enthusiast with some of the necessary upgrade’s needed to enter the modern performance era. Look for more follow up articles along with the LSX Conversion Handbook that will be released by HP books in their 2010 product line.

Making BIG Power

In addition to getting these engines into a classic car, it is possible to make extreme power with simple bolt ons. Once the LS engine is in you can chose to make engine upgrades to get that healthy rumble.

The pros over at Comp Cams can definitely help with these upgrades. LS performance has gotten to the point that the SBC is no longer Comp’s best selling engine cam for the first time since the SBC was developed! The LS engine line now accounts for more cam sales than any other engine and would explain the 27 cam options that Comp’s now has under their ever expanding LSR product line. To build off the numerous cam packages, Comp released the Fast EFI LS intake manifolds, fuel injectors with matching Big Mouth throttle body.


FAST’s new LSXR Intake is just one of the many popular upgrades from the COMP Performance Group for LS engines.

This tremendous support from GM and the aftermarket has created an ever expanding aftermarket for LS based conversions that will only continue to grow with increased options for every enthusiast’s budget! With all of these options available, there’s no reason that you can’t have the best of both with your vehicle – classic looks with modern day reliability.