LS Gen IV Engine Overview
The LS engine family began with what GM refers to as the Gen III engine platform, which included the LS1 and LS6. The Gen IV family began with the LS2 and includes LS7, LS3, LS9, and L92. Although the LS2 engine shared the cathedral intake port head design that carried over from the earlier LS engines, the LS2 falls under the Gen IV category basically because the camshaft timing sensor moved to the front of the block, whereas earlier blocks featured the cam sensor at the rear. This is the only reason the LS2 is referred to as a Gen IV engine.
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All Gen IV LS engines feature a front-mounted cam position sensor (mounted to the front timing cover), with cam timing picked up by reluctor blocks on the camshaft gear.
LS2 Differences
The primary differences between the LS2 and other Gen IV engines involve increased displacement and cylinder head design. The LS2 offers 6.0L of displacement while the LS3 and LS9 feature 6.2L, with the LS7 providing 7.0L of displacement.
Of the various differences in cylinder head design, the most notable involve the intake ports. The LS2 heads feature the tall cathedral ports (similar to the intake ports found on LS1 and LS6), while the LS7, LS3, and LS9 heads feature a rectangular intake port design (often referred to as square ports, although they are actually rectangular).
This ready-to-install LS aftermarket crate engine featuring LS3 heads is available in horsepower ranging from 540 to 660. Thanks to LS cylinder head design and the appropriate cam profile, such horsepower numbers have become commonplace.
This LS7 engine is being fitted to a 1969 Camaro. While creative turbo plumbing was required during fabrication and test fitting, engine and transmission installation was relatively straightforward thanks to readily available LS-swap mounts.
Performance Gains
The performance automotive aftermarket’s prompt and enthusiastic support for the LS platform made horsepower gains possible through wide-ranging development and by offering stronger forged crankshafts, varying crankshaft strokes, stronger forged connecting rods in lengths suitable for varying stroker combinations, and forged-aluminum pistons in a wide range of bore diameters, compression heights, and dome volumes. Roller camshaft profiles are available from all leading aftermarket cam makers to suit any desired build in terms of horsepower, torque requirements, and power bands. To provide much more durable threaded fasteners for the LS, stronger billet-steel main caps, cylinder head bolts or studs, main cap bolts or studs, and rod bolts are offered, all designed for torque-value installation, eliminating the need for torque-plus-angle tightening.
It’s become rather commonplace for dual-turbo LS engines to produce well beyond 1,000 hp.
Aftermarket forged-aluminum pistons are offered for LS applications in a full range of diameters, compression heights, and dome volumes and configurations to suit any conceivable requirement.
The majority of LS factory engines feature powdered metal main caps. While suitable for street and some racing applications, a move to steel-billet main caps provides added bottom-end strength. Aftermarket blocks are commonly available with either ductile-iron or steel-billet caps.
Some factory LS engines, such as the LS7, are already fitted with steel-billet main caps. These OEM four-bolt main caps provide the strength to support more than 500 hp and 481 ft-lbs of torque.
LS cylinder heads are critical power makers due to their superior flow. Aftermarket head manufacturers have developed and refined the LS designs for even better flow by means of cathedral or rectangular intake ports and a wide range of valve sizes and combustion chamber volumes.
Based on the original GM LS cylinder head designs, sophisticated aftermarket cylinder head innovations have been developed that boost power well beyond that offered by the factory heads. Choices include Gen III and LS2 cathedral-port heads and Gen IV rectangular-port heads, with intake volumes ranging from about 225 cc to more than 255 cc, along with premium stainless-steel valves and improved flow designs for both straight and offset intake rocker applications and fully CNC-machined ports and chambers. The primary “secret” of LS power lies in the cylinder head designs. While factory heads such as the L92 style are excellent platforms, the aftermarket has really stepped up to provide power well beyond the OEM offerings.
Aftermarket forged cranks provide added strength and are available in a variety of strokes. Both standard and super-lightweight versions are offered, covering the needs of both street and extreme racing applications.
OEM rocker arms perform well, but aftermarket performance full-roller rockers enhance performance and durability with forged-aluminum bodies, hardened pushrod cups, heavy-duty caged trunnion bearings, and roller bearing valve tips. In comparison, the factory powdered metal rockers, which feature roller bearing trunnions, have frictional contact with valve stem tips. Aftermarket full-roller rockers are better able to withstand high engine speeds and higher cam lifts while offering reduced friction due to the roller bearing contact at the valves. Aftermarket rockers are also readily available in both a standard 1.72:1 ratio and a 1.8:1 ratio.
If you plan to reuse the factory rockers, you must upgrade to aftermarket fully caged bearing trunnions; factory uncaged bearings can dislodge.
Aftermarket full-roller rocker arms offer superior strength and reduced friction because roller bearings contact the valves instead of the OEM frictional contact design. Aftermarket performance roller rockers are available in both 1.72:1 and 1.8:1 ratios.
The aftermarket has stepped up to offer both iron and aluminum LS blocks that provide more latitude in overboring and stroking, in addition to enhancements that provide superior oiling, cooling, and, most important, strength.
The LS builder is no longer limited to the factory plastic lifter guide trays. Also available are tie-bar link lifters that provide superior precision by keeping lifter rollers in plane with the cam lobes. High-quality aftermarket lifters also offer superior strength for higher valve spring pressures and to accommodate higher engine RPM.
Retrofitting the LS
While factory lifters are individual and are guided within plastic guide trays, aftermarket choices now include lifters that retrofit to these plastic guides and link-bar-paired roller lifters that eliminate the plastic guides. In basic terms, the aftermarket fulfills the requirements of performance and racing applications by addressing the various weak points of the factory designs both to boost power and to provide a much higher level of durability for high-stress application environments.
This Tech Tip is From the Full Book, LS GEN IV ENGINES 2005 – PRESENT: HOW TO BUILD MAX PERFORMANCE. For a comprehensive guide on this entire subject you can visit this link:
LEARN MORE ABOUT THIS BOOK HERE
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A full range of additional components is readily available to increase power and durability, including viscous-dampened crankshaft balancers, improved-flow mechanical and electric water pumps, and enhanced-design timing covers that provide additional timing chain clearance and allow cam timing changes without the need to remove the crank pulley. Improved oil pan designs are now available that provide added capacity and reduce windage concerns. Also offered are more-robust and powerful ignition coils, taller valve covers that provide clearance for aftermarket rockers, adapters that permit installation of Gen I small-block Chevy valve covers, a variety of intake manifolds for both injected and carbureted applications, and easy conversions to allow the use of carburetors on LS engines. Forced induction systems are also readily available, including both supercharged and turbocharged applications.
Electric water pumps are popular among many builders and are now available for LS applications. Depending on your belt routing requirements, these pumps are offered with or without an idler pulley.
For those who wish to run their LS engines carbureted, a variety of intake manifolds are available in dual-plane, single-plane, low- and tall-profile, and single- or multiple-carb designs. These manifolds are also offered without injector bungs or with injector bungs for those who wish to run a central-mounted throttle body with per-cylinder injectors.
Unlike the early days when the LS platform was considered the “new and unique” performance engine, thanks to the performance aftermarket we now have total coverage in performance upgrades; that is, for every single component involved in a build. Regardless of your goal, whether that involves a mild street upgrade or full-blown competition in any form of racing, including drags, road racing, oval track, etc., if you’ve got the money, the aftermarket can feed your addiction.
Aftermarket high-performance ignition coils offer superior output, reliability, and appearance over factory coils.
Example of a custom-built LSX LS7 street/competition engine featuring a FAST intake manifold. (Photo Courtesy Livernois Engines.
Although factory blocks can handle minor to major power enhancements, aftermarket blocks in both cast iron and aluminum offered by manufacturers such as Dart, Racing Head Service (RHS), and World Products provide notable improvements and versatility. Aftermarket blocks allow builders to obtain larger cylinder bore diameters and accept longer crank strokes, along with vastly improved strength and durability, giving engine builders much greater latitude in achieving more power, torque, and reliability. Thanks to support from the performance aftermarket, achieving naturally aspirated 600-plus hp is extremely easy, with forced-induction builds reaching 1,000hp and beyond.
Factory connecting rods on most LS engines are powdered metal construction. The factory rods are suitable for power up to around 450 hp or so, but it is strongly recommended to swap to forged-steel aftermarket rods, which are available in various center-to-center lengths to accommodate standard or stroker applications.
Upgrading critical fasteners in cylinder head, main cap, and rod bolt applications is essential for any high-horsepower build. Not only do quality aftermarket fasteners provide superior tensile strength, they are specified to use a torque value only, an easier installation than the factory torque-plus-angle tightening method. Unlike factory fasteners that are torque-yield one time use, quality performance aftermarket fasteners may be reused, obviously based on condition.
Because of the increased popularity of the LS platform, more and more restoration builders choose LS transplants for older muscle car applications, spawning a range of engine swap kits. Components developed to ease installation of the LS engine into older vehicles include motor mounts, frame adapters, plug-and-play controller systems for factory-type injection applications, exhaust systems that allow LS engine adaptations into a variety of popular muscle car and vintage vehicles. Essentially, all the types of power-adding and increased-durability components developed over the decades for Gen I engines are now available for the LS platform, making it the most popular standard for Chevy performance applications today.
Instead of using the factory crankshaft pulley, aftermarket balancers are available with or without grooved pulleys. The viscous-dampened balancers provide additional reduction of harmonics. These are available for either unkeyed factory-type crank snouts or keyed for aftermarket cranks.
Written by Mike Mavrigian and republished with permission of CarTech Inc
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