The General Motors (GM) Gen III LS1 V-8 is one of the many successful engines to come out of GM Powertrain since it was formed to be the global powertrain provider for GM. As this book goes to print, about 8,000 Gen III small-block V-8 engines are built each day, in multiple cubic inch and power combinations, in multiple plants all over North America. These engines are the production powerplants for everything from Chevrolet Corvette sports cars and Australian Holdens (the Pontiac GTO in the States), to GMC Yukon SUVs and any of the V-8- powered Chevrolet and GMC pickup trucks. They’re also sold as crate engines by GM Performance Parts and marinized versions are sold by GM Powertrain.
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Gen III LS1 V-8 Usages
The Gen III V-8 is built in four displacement sizes, with three initially using a cast iron engine block and one using an aluminum block. The most well known Gen III V-8 is the 5.7-liter all aluminum engine — known by its three-digit alphanumeric regular production order (RPO) engine code: LS1 (all GM engines are denoted by an RPO code). The LS1 was the first version of the Gen III V-8 architecture to hit the streets in the 1997 Chevrolet Corvette and then soon after in the Camaro and Firebird. It made such an impression that the majority of automobile enthusiasts call all the Gen III V-8 engines an LS1, whether it is a Vortec LQ9 in an Escalade or a LS6 in a Z06 Corvette.
The 6.0-liter cast-iron block, aluminum-head, Vortec-branded LQ4 and LQ9 truck engines will also be covered extensively in this book, as automotive enthusiasts usually lean toward engines with bigger displacements. The LS1 and LS6 are the performance engines from GM, and the LQ4 and LQ9 are the biggest displacement production Gen III V-8s available, so it is easy to understand why this book would focus on them.
There will also be some discussion of the two other Gen III V-8 variants, the 4.8-liter LR4 and 5.3-liter LM7 cast-iron block, aluminum-head engines. These are very common in trucks and SUVs. The 4.8- and 5.3-liter engines use common architecture to the LS1 and LQ Gen III V-8 engines, so the information presented on the 5.7- and 6.0-liter Gen III components and modifications can be applied to them. They won’t be discussed as much as the 5.7- and 6.0-liter Gen IIIs because these smaller engines won’t make the same amount of power for the investment of time, effort, and money due to their smaller displacements. But many of the upgrades performed here will work on the 4.8- and 5.3-liter engines, so if that’s what you’ve got to work with, they will respond to improvements. In fact the 4.8/5.3 castiron block can be bored out to a 5.7-liter bore size – all the more reason to discuss 5.7-liter performance packages.
As you’ll see, later chapters in this book have specific engine buildups on 5.3-, 5.7-, and 6.0-liter engines to give you “recipes” for making certain levels of power. Also, there is a racing-only aluminum engine block available from GM Performance Parts, called the C5R, which will be used as the foundation for a 1,000+ hp engine later in the book.
The Details to Make Horsepower
This chapter will give you the technical information regarding the basic materials, manufacturing processes, and assembly methods used by GM to create the Gen III V-8. There is a plethora of details and minutia we could bury you with here, but instead of trying to teach you how to design an engine for mass production, the information shared in this book is focused on helping you create performance with the existing Gen III V-8 engine.
To that end, the details listed here usually have explanations on why they were done and how they impact the performance of the engine. Possibly more important, the usages of the Gen III V-8 are discussed along with how to identify the various engines and components, so you can find desirable engines and components using external and internal visual clues. You can combine this info with the info in the next chapter to decide which factory components are desirable when building a productionbased performance Gen III V-8.
(All part numbers (PN) were gathered in 2003 and are subject to change at any time.)
The LS1 and LS6 version of the Gen III V-8 block is created using a semi-permanent mold casting process with 319- alloy aluminum heat-treated to T5 specs. The block design is a tour-de-force of technology to maximize strength while minimizing weight and noise. The design was mainly done with the aluminum material in mind, so the iron block is much stronger than any previous GM production iron block. The Gen III team knew a strong block would be needed to maintain round bores for maximized fuel economy and performance while minimizing durability issues and emissions, so that’s what they built. To do all that, the head bolts pull from the main webs, the crank main caps are cross-bolted on the deep skirt block, and the design was fully evaluated with finite element analysis (FEA) computer modeling to add ribbing in areas that required increased rigidity.
Bore centers are at the traditional small-block Chevy 4.40 inches (111.76 mm), but the cylinders themselves are the story. On the aluminum LS1 and LS6 engine blocks, each bore is actually a thin, centrifugally cast iron liner with a serrated outside diameter. The liners are cast in a centrifuge to maximize the density of the iron, and then cast in place with the block. The thin liners limit how much the 3.898-inch (99-mm) inside-diameter cylinder bores can be machined out — GM recommends the ’97 to ’98 LS1 blocks be honed only 0.004 inch and ’99 and later blocks can only be machined 0.010 inches. The serrated outside diameter surface helps to lock the liner in place in the block and dissipate heat through the increased surface area. The fact that GM figured out how to hold these liners to such tight tolerances during the casting process is an impressive engineering feat.
The iron engine blocks don’t have cylinder inserts. Because of this, the 4.8- and 5.3-liter iron blocks can be bored out to 99 mm (from the 96 mm original bore) to build an iron version of the 5.7- liter engine (the 4.8-liter engine needs the 3.662-inch stroke crank to attain 5.7 liters of displacement). The 6-liter engine block’s 4.000-inch (101.6-mm) cylinder bores are nearly the max for wall thickness, so it isn’t recommended to bore these out for more cubic inches.
The Gen III V-8 cylinder heads have replicated ports and combustion chambers similar to many aftermarket, high-performance cylinder heads offered for past small-block and bigblock GM pushrod V-8s. This means all eight cylinders use the same shape ports and combustion chambers, which allowed the engineers at GM to focus on optimizing just one combo of ports and chamber shapes. Doing this made it easier to maximize power and efficiency in the overall engine while minimizing emissions.
The distance between the exhaust and intake valve guides and hence, the valves, is common for all the production Gen III V-8 cylinder heads. This was viewed as a power potential limiter by the port, chamber, and valvetrain engineers, but was done to minimize tooling investment and simplify manufacturing. Changing the valvestem centerline spacing is a big job, but it’s acknowledged that moving them around to work with bigger intake valves will release more power potential.
The small chamber volumes of all the cylinder head variations provide excellent quench area to work with the flattop pistons. This helps to put all the air/fuel mixture in a tight area to maximize the combustion process and provide the maximum force pushing on the piston.
The high-output LS6 features cylinder heads with higher-flowing ports and chambers compared to the base LS1, but the heads aren’t the only reason for the increased power output. A more aggressive camshaft, freer breathing airbox and mass air flow sensor (MAF), lightened valvetrain components, and various other pieces took advantage of the improved ports and more efficient combustion chamber for higher RPM and more power production throughout the powerband.
The reason this needs to be explained is so you don’t bolt on a set of LS6 cylinder heads and wonder why you didn’t get a huge leap in performance! Better flowing cylinder heads require all those additions and possibly a freer flowing exhaust to take advantage of the increased flow capabilities. The heads are the core part of the success with the Gen III V-8, but you’ll need to enable them to make the power potential they contain.
The Gen III LS1 V-8 engine crank is made of nodular cast-iron but has far superior strength to what most would think of from a cast crank. This is because the Gen III crank has rolled fillets on the journals to reduce stress risers and variable-radii undercuts on the counterweights to increase the bearing surface area.
Rolled fillets are created by a roller being forced into the edge of the crank bearing edge around its circumference to compress the material into the shape of the smooth transition. This minimizes the chances of a stress riser, or crack, forming in this area by compressing the material in this area and eliminating a sharp edge where the crank transitions from a machined surface to the as-cast portion of the crank.
The crank also has a 0.9645-inch (24.5-mm) hole drilled through the number 2, 3, 4, and 5 mains to reduce its overall weight 143 lbs (65 kg) and allow air and oil vapor to flow through the holes between the cylinder bays to improve bay-to-bay breathing.
Automotive enthusiasts have found the “cracked,” powdered-metal Gen III V-8 connecting rods weigh less and handle just as much power as the famed Chevy “pink” rods. In case you’re wondering, the Gen III V-8 rods are called a cracked rod because the big end cap of the rod is created through a cracking process. It goes like this — after the rod is created, a groove is machined on the inside diameter of the rod’s big end where the parting line is intended. Then, a side load force is applied to the rod to split off the cap portion of the rod. When torqued in place, the two pieces mate up precisely and lock tightly together on the jagged micro-edges of the break.
The rod itself is made from powdered steel that is packed into a mold under pressure and heated to just below the melting point of the steel to get the steel to bond. A forging process is then performed, followed by shot peening, to end up with a rod of very predictable size and weight. This eliminates the need for material pads at each end of the rod (like on the pink rod) and machining to get the proper sizing, balance, and lengths.
As with the cast crankshaft, the piston material, cast eutectic aluminum, is not usually thought of for high-performance applications because many consider them more brittle than forged aluminum pistons. However, these pistons work in this application because the engineers at GM did their homework to create a design that is light, seals the bore, and works well with the combustion chamber. As a testament to their ability, it is widely accepted that the stock pistons can handle just over 500 hp before needing to be replaced by aftermarket forged pistons.
Since the pins are pressed into these lightweight pistons, some performance engine builders do not like to remove and reinstall these pistons more than once to minimize the chances of introducing stress risers in the piston pin bores.
If you do swap aftermarket forged aluminum pistons into your Gen III, the factory knock sensors will likely need to be disabled or desensitized in the factory powertrain control module (PCM) software, as the forged pistons “sound” like combustion detonation to the knock sensors. You’ll know this is true when the “Service Engine Soon,” or SES, lights up during operation with the forged pistons.
Some might write off the Gen III V-8 as crude because it is a cam-in-block, pushrod V-8; but don’t be fooled. While the basis is simple, the engineers at GM spent considerable time and effort to create a system capable of high performance.
The factory camshaft is gundrilled to reduce weight and actuates hydraulic roller lifters that allow for aggressive cam lobe shapes. The rockers are investment cast with a roller fulcrum for light weight and minimal frictional losses. The valvesprings are coiled in varying diameters with oval-shaped wire, so they look like a “beehive” and are called so. These springs eliminate the need for a damper spring inside the main spring and the ovate wire helps to improve the high-rpm valve control.
The camshaft is a large diameter as compared to previous small blocks, which improves rigidity to provide increased valvetrain stability at high engine speeds.
The Gen III V-8 oiling system improves on the simple yet effective design of the Gen I and II small-block V-8s. The oil pump is no longer driven by a shaft connected to the distributor, like on the Gen I and II. Instead, the pump is a gerotor design that slides over the snout of the crankshaft. The pressurized oil flows out of the pump body into a main galley that runs lengthwise down the driver side of the block. At the end of the main galley, the oil flows down through a fitting on the oil pan, through the oil filter, and then up a passage in the back of the block into the lifter galley passages that oils the rest of the engine.
Oil control is very important to GM as higher oil pressure ties up horsepower in pumping losses and increases oil consumption, which can lead to higher emissions. Because of this, any performance upgrades should be accompanied by increased spring pressure on the oil bleedoff spring in the oil pump and a simple port job on the oil-pump outlet to insure maximum oil flow.
The Gen III LS1/LS6 V-8 intake manifold is impressive for its low height, light weight, and high flowing characteristics. The intake is made with injected nylon and has a wall thickness of 3 mm. The injector bosses are located at the end of the intake manifold ports, pointing directly at the back side of the intake valve head. The air enters the intake manifold at the front through a mass airflow (MAF) sensor and throttle body. The airboxes and connecting tubes on the Corvette, Camaro, and Firebird are located just over and in front of the radiator. This was done to maximize laminar airflow into the engine and minimize engine heat from increasing the temperature of the intake air.
The higher-flowing ’01 LS6 intake was standard across both LS1 and LS6 in ’01 and beyond and is highly sought after for its ability to increase power output as a simple replacement of the pre- ’01 intake.
The truck manifold has similar lowRPM, low-valve-lift flow capability of the LS1 intakes, but doesn’t have the same flow figures at high rpm. This makes sense, as trucks are used more in the low to mid-RPM range. The truck intake is approximately 3.11 inches taller overall than the LS1 intake and the throttle body mounting point is about 3 inches taller than the LS1. This is to clear the radiator/fan clutch/fan on the trucks.
Electronic Fuel Injection
The fuel-injection system on the Gen III LS1 V-8 is sequential. This means each injector opens to release fuel into the intake port just before the intake valve opens. Previous GM fuel injection systems were batch fire or bank fire. With a batch-fire system on a V-8, all the injectors open eight times for each complete firing sequence of the engine. On a bank-fire system, the injectors on each bank of the engine open four times per complete firing sequence of the engine. On a sequential fuel-injection system, each injector opens only once per complete firing sequence. The sequential system doesn’t offer a big leap in power output, but it reduces emissions while improving low-RPM driveability and fuel mileage.
The calibration to operate the sequential fuel-injection system is exponentially more complex than a batchor bank-fire system. It uses many sensors on the engine and vehicle to make its decisions. The Gen III V-8 is equipped with very advanced crank and cam position sensors, so the PCM can quickly determine which cylinder is the next to fire to initiate the fuel injection. The crank sensor is located next to the starter on the passenger side of the engine and the camshaft sensor is located at the back of the engine above the lifter valley. The crank has a 24x reluctor wheel on it, which means it is a wheel with 24 steps on it so the computer can read where the crank is in its rotation very quickly. The cam sensor has a 2x shape into it, which allows the computer to quickly determine where the crank is in the four-stroke cycle of the number-1 cylinder and fire the appropriate injector and spark plug to run the engine.
Simply put, GM has invested in engineering resources, along with tooling and piece costs to create a sequential fuel-injection system that produces impressive emissions, fuel consumption, and driveability results.
Electronic Controls and Calibration
Probably the most complex system on the Gen III V-8 is the powertrain control module (PCM). So far there have been two PCMs for the Gen III.The first is called the “cast” controller, a name given for its external case. The PCM used now is called the P59 within GM, and has computing capability on par with a home computer. The reason for the increased computing power is the size and complexity of the calibrations. The Gen III V-8 calibration started as a 375-kb file that had jumped to a little over 1 Mb in size in 2003. The calibration is made up of many, many tables that cross-reference each other, so it’s very complex. The reason for the cross referencing is to take advantage of the ability of the sequential fuel-injection system to alter fuel and timing many times per degree of crank rotation based on input from various sensors located on the engine.
One of the great advantages of the electronic PCM is its ability to diagnose issues through data interpretation. Late-model performance enthusiasts often talk about codes or DTCs they are experiencing. This is a reference to the on-board Diagnostic Trouble Codes (DTCs) that are issued by the PCM when it deduces a problem exists. The driver will be notified through the SES, or Service Engine Soon, light on the dashboard being illuminated, that an issue exists. To see which of the 2000 or so DTC codes is causing the SES to come on, a Tech II or other style of scan tool is plugged into the data link connector under the dashboard of the vehicle.
The coil-near-plug design of the Gen III V-8 ignition is often called a coil-on-plug design, but that’s inaccurate. On the early prototype Gen IIIs, the coils were located on the plugs, but they didn’t survive early testing schedules due to the exhaust manifold temperature. To cure this, the coils were moved to the valve covers with a shorty spark plug wire connecting them to the plug.
The PCM tells the coils when to fire the spark plug. The PCM references the 24x crank trigger and the single-phase (2x) cam location sensor located in the lifter valley to know where the crank is in its 360-degree rotation and what cylinders are on the compression stroke.
This angle-based system is different from most aftermarket controllers, which work in 90-degree time increments. The reason the angle-based system is used is because it is more accurate than the time system, which makes it possible to reduce the emissions and increase driveability.
As a tip, the truck coils have slightly larger heat sinks, so many Gen III enthusiasts believe they are better suited for high-horsepower, high-heat applications.
The exhaust manifolds on the early Gen IIIs were pretty high-tech to get the catalytic converters up to temperature very quickly to minimize startup emissions. The ’97 to ’98 car-based Gen III LS1 V-8 engines used fabricated exhaust manifolds that were made of 0.8-mmthick 309 stainless steel inside a 1.8-mm 409 stainless steel wall, with a 3-mm air gap between the two walls. This obviously expensive exhaust manifold was replaced with a conventional cast iron manifold in the 1998 model year vehicles once the engine management was improved enough at startup to keep the emissions in line.
Beyond the manifolds, the factory exhaust systems all have O2 sensors before and after the catalytic converters. The onboard diagnostics (OBD-II) software in the PCM is always comparing the inputs from the O2 sensors, expecting to see improved emissions on the downstream sensor. This way, when the converter starts to loose its effectiveness, the SES light comes on. This light will also come on if the catalytic converter is removed.
An interesting point to note is the placement of the O2 sensors. Almost always, the sensors will be pointing down into the tube to minimize the chances of moisture collecting on the sensor. Also, a standard of O2 placement on tube headers is to have it 8 inches down from the merge-point of the primaries into the collector — when you have 2-inch primaries.
There are four oxygen sensors in the exhaust system, while there are only two catalytic converters. The exhaust tubes are stainless steel for the Corvette/Camaro/Firebird from 1997 to 2003, except for the Z06 exhaust, which is made of titanium for lighter weight.
Front Accessory Drive
The Corvette and Camaro/Firebird front accessory drives are mostly common, while the truck Gen III V-8 engines use multiple front drives. The difference is the placement of the A/C compressor, power-steering pump, and alternator.
The F- and Y-body car systems use a single belt to run everything but the A/C compressor, which runs on its own belt to minimize NVH.
The LS1 F-car front drive will work in most hot-rod applications. Here are the part numbers to assemble a complete front engine accessory drive (FEAD).
The LQ4 and LQ9 6.0-Liter Gen IIIs
The Gen III engine many automotive enthusiasts desire is the 6.0-liter and it comes in two varieties. The GM names for these two engines are the LQ4 and LQ9. The LQ9 engine is the high-performance 345-hp version that was first available only in the Cadillac Escalade. The 300-hp LQ4 is available in many full-size Chevy and GMC trucks and SUVs. The external differences between these two engines are slight, but you can still determine the type of engine using available internal and external clues.
Short Block: cast-iron block, cast crank, powdered metal rods, cast aluminum pistons (with coated thrust faces and domes)
Top End: aluminum heads with 72- cc combustion chambers, plastic truck intake, iron heads on ’99-’00 LQ4, aluminum on both engines after ’00
Fuel/Air/Spark: crank-trigger activated, sequentially fired EFI system, coilnear-plug ignition system
Valvetrain: hollow factory camshaft, hydraulic roller lifters, investment-cast rockers with a roller fulcrum, and beehive valvesprings
They weigh approximately 520 lbs fully dressed and are the same external size as the LS1/LS6. The 6.0-liter LQ4 and LQ9 block casting numbers are 12551364, 12573581, and 12577184.
Building a High-Performance 6.0-Liter Gen III V-8
You can put together a high-performance 6.0-liter with some simple GM parts swapping. The high-performance LS6 cylinder heads and intake will bolt directly to a 6.0-liter engine (the stock LQ4/LQ9 intake is not designed for high-RPM power, but will make excellent power in the low to midrange powerband).
In fact, bolting the LS6 cylinder heads on a 300-hp LQ4 is similar to the recently released LS2 6.0-liter performance engine in the ’05 C6 Corvette. There is an issue with compression ratio on the LQ9 swap, as it already has a 10:1 compression ratio with the 72-cc LQ cylinder heads. Bolting on the LS6 heads, with their 64-cc chambers, will require a piston change to get back to a streetable 10:1 compression.
As a note, the blocks are the same on the 300- and 345-hp 6.0-liter engines, as are many other internal components.
The pistons are beefier on the LQ engines than on the LS1 engines, and they are easy to differentiate from each other. The pistons on early LQ9s have a top and side coating, while later versions of the LQ4 pistons are coated.
If you plan on making over 400 hp with the LQ9 or LQ4, it is recommended the engine be disassembled and the bores be honed with a surface plate on the engine before adding some aftermarket forged pistons. This process will ensure bore symmetry and prepare the bore for the new pistons. Many engine builders feel the factory cast-aluminum eutectic pistons are not as robust to high cylinder pressure situations where detonation and preignition have a higher tendency to occur, which is why it is recommended they be replaced with forged aluminum pistons.
Quality Built Engines
In 2002, the Gen III engine architecture was rated as one of the most trouble-free V-8 truck engines in North America, according to J. D. Power survey results. The 5.3-liter truck engine achieved a rating of 9 problems per 100 engines (“problems per hundred” is a J.D. Power standard abbreviated as pph) in 2002. This is impressive, as the Toyota 4.7-liter V-8 had 13 pph and the Ford 5.4-liter V-8 had a 17-pph rating.
In 2002 alone, the GM engine assembly plants produced over 1 million Gen III V-8 engines. On average, it takes about 4.5 hours to build a Gen III engine in the assembly plant, and many plants can build up to 4,000 engines per day. If you do the math, you’ll find that millions of Gen III V-8 engines have been produced since 1997.
The GM engine assembly plants use sophisticated systems to eliminate assembly problems and then document these solutions so the other Gen III assembly plants benefit from that one plant’s work to improve quality. One way they do this is by testing a part to make sure they are within specification every 60 or so pieces. Every engine is run through a cold-test that checks over 400 parameters in systems like the ignition, oiling, valvetrain, and more to insure the highest quality. There are even high-tech machines that check every threaded hole in the engine block before it enters the assembly plant to ensure the threads are good.
This last issue was a big one in engine manufacturing for years, but with this new machinery, cross-threading problems have been minimized. This has allowed engine plants like Romulus Assembly, located just outside Detroit, to go from 125 problems per million (ppm) to 0. This technology was quickly integrated into the plants in St. Catherines, Canada, and Silao, Mexico. In general, 99.98 percent of Romulus’ engines exit the assembly plant free of problems.
The result of this problem-solving innovation has been high productivity and excellent quality from all the assembly plants, and awards in highly prestigious benchmarks like the Harbour Report — which awarded the Romulus Engine plant the “most productive V-8 Plant in North America” in 2002.
Written by Will Handzel and Posted with Permission of CarTechBooks
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