Читать книгу LS Gen IV Engines 2005 - Present - Mike Mavrigian - Страница 8

CHAPTER 2

ENGINE BLOCKS

Engine blocks in the LS family share similar characteristics, with deviations primarily based on cylinder bore size. One of the primary differences between Gen III and Gen IV blocks is the relocation of the camshaft position sensor, which was moved from the Gen III location at the rear top of the block to the timing cover on Gen IV engines. All factory production blocks, whether cast iron or aluminum, feature six-bolt main caps, with four primary vertical bolts and one 8-mm side bolt at each side of each main cap. All LS production blocks feature powdered metal main caps except LS7 and LS9 engines, which feature steel-billet main caps for added strength. In comparison to earlier blocks, LS3 and LS9 blocks feature additional reinforcement in the main web areas. LS9 blocks were designed for supercharging forced induction, so they feature larger bulkhead windows for improved bay-to-bay breathing; larger-diameter 12-mm head bolts; and piston oil squirters in the cylinders.

Block Specs

Block Part Numbers
LS2	12568950
LS3	12584727
LS7	19213580
LQ9	12572808

Stock Blocks

Factory and aftermarket blocks are substantially different from one another. Factory blocks are mass-produced with wide tolerances permitted as “acceptable” for common street applications. For example, while the factory specification for LS block deck height is 9.240 inches, OEM blocks rarely meet this spec. It’s rather common for a block to feature greater and/or lower deck height on any particular block, with deck height varying from low to high along either bank. This means that the decks may not be parallel to the crankshaft centerline. While this may not present a problem for the average street engine, if your goal is to obtain maximum power, decks must be checked and likely corrected to achieve the same cylinder volume for all cylinders. Due to shifts in block geometry that result from the casting process, some cylinder walls may be thinner than others. The list goes on, but you get the point. If you wish to achieve maximum results for a power build, a factory block will likely require several corrective machining operations to “accurize” the block.

Unlike other LS blocks that feature powdered metal main caps, the LS7 comes from General Motors with steel-billet main caps.

In contrast, high-performance aftermarket blocks feature design enhancements such as thicker decks, stronger main webs, improved cylinder cooling, and improved oiling circuits, in addition to more precise CNC machining. Granted, a new bare block will need to be final-machined for the desired block deck height, lifter bore and cylinder bore diameters, and other dimensions. This final machining is by design: The manufacturer provides extra material that allows you to custom-fit your specific components. In addition, aftermarket block makers provide much greater attention to detail in terms of raw machining, wherein crankshaft centerline, camshaft centerline, lifter bore spacing, and cylinder bore centerlines are already spot-on. While correcting an OEM block may force you to compromise in terms of certain dimensions, with a quality aftermarket block you can obtain exactly what you want.

The LS7 features pressed-in cast-iron cylinder liners that are the biggest cylinders in the LS lineup. The race program provided data that was used to develop a light, rigid block. The deep-skirt configuration provides exceptional strength. The bulkheads hold six-bolt, cross-bolted main bearing caps that mitigate crank flex. This is the front view of an LS7 block.

The LS2 features a 4.000-inch bore and a 3.622-inch stroke. In contrast to earlier Gen III blocks, the LS2 cylinder head bolt holes are blind and not open to water. Note the four-lug cam timing reluctor for the front-mounted cam position sensor on this cutaway of the LS2 6.0L aluminum block, deviating from the Gen III rear-mounted cam sensor.

The rear view of an LS2 block cutaway shows the bay-to-bay breathing openings at the bottom of the cylinders, typical of all LS blocks. The LS2 block is very similar to earlier blocks, with changes made to the cam position sensor location and blind head bolt holes.

Even though factory blocks have been proven to handle drastic horsepower increases, such as builds configured with single or twin turbochargers that produce 1,000 hp and beyond, longevity and durability are key issues. These blocks were not designed to withstand the level of high combustion pressures associated with such power levels. In my opinion, and in the opinion of many other engine builders, if you plan to increase power this dramatically, upgrading to a stronger aftermarket block greatly reduces the risk of catastrophic failures that could result from excessive cylinder bore distortion and over-stressed main webs. If a build is planned to produce more than 700 hp, a stronger and beefier aftermarket performance block provides a much more reliable and stable platform for the build. Aftermarket performance and racing blocks feature thicker decks, stronger main webs, enhanced priority main oiling systems, thicker cylinder walls, vastly improved bay-to-bay crankcase breathing, and stronger-grade materials in both alloy and iron configurations.

Modifying the Stock Aluminum Block

Modifying a stock block can involve both corrective and enhancement processes. It’s very common for stock LS blocks to have uneven and out-of-specification decks. While the spec deck height is 9.240 inches, you may find blocks that have slightly taller or shorter decks. In addition, LS factory blocks tend to be out of square, with the front or rear of the decks being shorter or taller than the opposite decks. The decks can be resurfaced to make them the same height and parallel to the main bore centerline, using the shortest area as the index. Making the decks parallel to the main bore centerline helps equalize the combustion area between the piston at TDC and the cylinder head combustion chambers, as well as equalizing pushrod length requirements from cylinder to cylinder.

Performance aftermarket blocks usually provide a bit of extra deck height, allowing you to achieve the desired deck height. Finishing to the desired deck height will allow you to make the decks parallel to the main centerline.

While GM LS blocks feature main caps secured with two primary bolts and two side bolts, some aftermarket blocks eliminate the side pinch bolts and feature a four-bolt main cap design.

If you intend to increase displacement by moving to larger cylinder bores, be aware that factory aluminum blocks have bore liners that are installed during the casting process. The liners are relatively thin, allowing an overbore of only about .005 inch to a maximum of about .010 inch. If you intend to go .010 inch oversize, a sonic wall-thickness gauge should be used to measure wall thickness before any oversizing is performed. Factory iron blocks can be oversized more, again assuming that you’ll have at least about .200-inch wall thickness once the bore has been machined. Factory iron blocks can routinely be larger than the specs given by .030 inch, with some capable of handling as much as a .060 inch oversize, again, only if cylinder wall thickness is not compromised. Not all factory blocks are identical due to core shift during the casting process, so each cylinder should be first checked for wall thickness.

Aftermarket blocks tend to provide thicker cylinder walls, potentially allowing larger oversizing, but always check with the block manufacturer for the bore diameter limitations. Always refer to the piston skirt diameter of the pistons that will be installed to determine the required piston-to-wall clearance. Piston-to-wall clearance can vary depending on the piston material and the intended use (street, street/strip, race, forced induction, etc.). Never finish cylinder bores unless you have the intended pistons in hand so that pistons can be measured for skirt diameter.

Lifter bores should also be checked both for diameter and for angle. Depending on the lifters being used, desired clearance can vary, with advised clearances of some aftermarket lifters in the .0015-inch area. Always measure lifter diameter and verify that lifter bores are sized appropriately for the lifters that will be installed. Although not extremely common, due to potential core shift in factory blocks, lifter bore angles may be not perfectly perpendicular to the camshaft. Using specialty aftermarket accurizing fixtures or with the use of CNC machining, lifter bores can easily be corrected if needed. If the process of correcting results in oversizing, bronze bushing can then be installed and machined to size.

This view of a six-bolt deck clearly shows the extra head bolt holes above and below each cylinder, inline with the cylinder centerline.

Aside from these modifications, clearance checking when using a longer-stroke crankshaft is always required, with clearances measured between crank counterweights and the block pan rails, connecting rod big end to pan rails and cylinder bottoms, and rod big ends to camshaft lobes. Naturally, this is done during initial test assembly before any machine work is done.

Disabling Performance-Robbing Displacement on Demand

For high-performance LS Gen IV engines, the displacement on demand (DOD), also called active fuel management (AFM), must be disabled because it will restrict performance. Many of the LS Gen IVs use this system, except for the LS7 block. It disables four cylinders during certain driving conditions, such as easy cruising with low engine load. The only purpose of DOD/AFM is to increase fuel economy, a factor that isn’t high on the priority list for most performance-minded owners.

When DOD is signaled, cylinders 1-4-6-7 are shut down by effectively disabling their valves and by cutting off the spark to their ignition coils. This happens when solenoids on the underside of the valley cover allow high-pressure oil to be delivered to a groove in the special two-part DOD lifter that causes a pin to collapse a spring-loaded pin in the lifter. The two parts of the DOD lifter are then free to move relative to one another. The cam lobe keeps pushing on the lifter follower, but the inner part of the lifter pushes against a coil spring at the top of the lifter to prevent the force from being transferred to the pushrod, so that the rocker arm does not push on the valve. When the DOD system turns on, the V-8 engine effectively becomes a 4-cylinder engine, saving fuel.

The oil passages in the DOD/AFM towers are open on this block, and at this stage, it’s ready for tapping and plugging.

When more power is required, the lifters are activated. The operation is controlled by the engine control unit (ECU) and four solenoids located in the lifter valley. The solenoids provide a pressurized oil signal to the roller lifters. The system is tuned to a specific camshaft profile, with different lobe profiles between AFM and non-AFM cylinders and different valve lash requirements. DOD/AFM lifters were utilized in various 2006–2015 Gen IV LS engines. Examples include 5.3L engines in various vehicle applications, 6.2L L94 engines in Cadillac Escalades, 6.0L L76 engines in 2007–2009 Chevy Avalanches, 6.2L L99 engines in 2012–2015 Camaros, and 6.0L L77 engines in Chevy Caprice models.

This factory LS7 block has the four-bolt-per-cylinderhead bolt layout, the siamesed cylinder bores, and the main cap side bolt holes. The siamesed bore provides additional strength to the block and the four-bolt head provides extra clamping force for high-horsepower output.

The oiling towers of this LS7 block are blank and not drilled open. Since some engine applications feature DOD/AFM and some don’t, a common casting was made, with towers drilled for oil passages when factory production called for the DOD/AFM feature.

If a more aggressive cam is installed, the DOD/AFM system must be disabled, requiring not only the cam change but also installation of different lifters and lifter guides. In addition, the ECU must be recalibrated. Any competent GM dealer’s service department can reprogram (reflash) the ECU to keep the computer from detecting the on-demand lifter deactivation. If this reflash isn’t done, the driver will see a check engine light illuminated on the instrument cluster.

Note that the LS7 block features the same oil pedestals in the lifter valley, but they are not drilled open; there’s no need to make modifications because this block is not equipped for DOD lifter deactivation.

Many builders elect to eliminate DOD/AFM because it is simply not needed when the goal is to gain full advantage of the engine’s performance at all times. Eliminating DOD/AFM requires plugging all oil delivery ports in the standoffs located in the block’s upper valley. If these ports are left open, internal oil leaks will result in low oil pressure. The oil ports in the valley can be plugged by drilling and tapping each port and installing 1/8-inch NPT plugs, but this should be done only on a bare block that will be properly washed and rinsed after machining operations.

Rivet Plugs

Lingenfelter Performance offers a slick alternative that can be handled even on an assembled block. This essentially involves installing an aluminum rivet plug in each port with the use of a manual rivet tool. This requires no machining, so the concern about leaving metal particles and shavings inside the oil passages is eliminated.

To install a rivet, put the rivet into the rivet tool. With the tool’s arms spread apart, insert the rivet into the oil port. While holding the tool against the port surface, squeeze the tool’s arms together to expand the rivet. Once the rivet fully expands, the rivet mandrel will snap off and remain in the tool. The aluminum rivet plug will seal the port with no additional sealing required. Lingenfelter’s installation tool is available as PN L950105305, which includes a set of rivets. Additional eight-rivet sets are also available as PN L960225305. This is a slick, easy, and no-mess method of sealing the oil ports on either a bare or assembled block.

The Lingenfelter rivet tool allows easy plugging of DOD/AFM oil ports in the valley stands. (Photo Courtesy Lingenfelter Performance)

With the rivet tool held against the stand, begin to squeeze the tool arms to begin rivet expansion. (Photo Courtesy Lingenfelter Performance)

After installing a rivet to the tool, insert the rivet into the oil port with the tool arms spread apart. (Photo Courtesy Lingenfelter Performance)

Continue squeezing the tool arms until the rivet fully expands and the mandrel snaps free. (Photo Courtesy Lingenfelter Performance)

No additional sealant is required. The aluminum plugs seal the ports and will not loosen. If you wish to eliminate the DOD/AFM system, these holes must be plugged to avoid a reduction of oil pressure. If an aggressive camshaft is being installed, the DOD/AFM system must be disabled. (Photo Courtesy Lingenfelter Performance)

DOD Delete Kits

Eliminating the DOD system isn’t complicated. This involves closing off the oil passages in the DOD towers, replacing the four cylinders’ intake and exhaust lifters with “regular” LS lifters, replacing the DOD-location plastic lifter guides with standard non-DOD lifter guides, replacing the camshaft with a non-DOD cam, and eliminating the solenoids by replacing the lifter valley cover. You can source all the items individually, or you can buy a DOD-elimination kit from General Motors or various aftermarket sources.

A GM Performance Parts DOD delete kit is available under GM PN 12570471. This kit includes a three-bolt 4X cam sprocket, ARP cam sprocket bolts, LS2 chain damper, LS7 lifter set, LS3/L92 head gaskets, OEM head bolts, exhaust manifold gaskets, LS2 valley plate, a set of four standard plastic lifter guides, PCV dirty air hose, PCV valve cover plug, and a new GM balancer bolt. Installing the kit also requires the use of an aftermarket camshaft that was not designed for use with DOD/AFM along with ECM reprogramming.

One example is Summit Racing’s PN CMB-09-0026, which includes a set of lifters, lifter guides, valley cover, and head bolts. Another DOD/AFM delete kit is Tick Performance’s PN 5065TP. This includes an LS3 valley cover, LS2/LS3/LS7/LS9/L92 lifter trays, a full set of LS7 lifters, head gaskets, head bolts, LS2/LS3/LS7/L92 timing chain damper, LS2 PCV hose, PCV cap, timing cover gasket, water pump gaskets, timing cover seal, and a GM crank balancer bolt.

While most factory production LS blocks feature powdered metal main caps (except the LS7, which features steel-billet caps) that use 8-mm side “pinch” bolts, some aftermarket blocks utilize steel-billet four-bolt main caps with outer splayed bolts, such as this example of a Dart LS Next block.

You can see the machined ends on the LS7 billet-steel main caps that accept the 8-mm side bolts. Doweled-in forged-steel main bearing caps provide excellent support for the crankshaft.

Main Caps

All GM factory LS blocks feature a six-bolt main cap design, with four primary 10-mm × 2.0 vertical bolts and two 8-mm × 1.25 “pinch” or “cross” bolts that pass through the lower block sides into the caps. All factory LS blocks also feature powdered-metal main caps except the LS7 and LS9 blocks, which use forged-steel main caps. Powdered metal caps have proven to be satisfactory for builds up to the range of about 500 hp. Beyond that horsepower range in a naturally aspirated engine, and especially if higher cylinder pressures are planned due to nitrous injection and/or forced induction, aftermarket forged-steel main caps along with stronger main bolts or studs, such as those offered by ARP and other sources, are highly recommended.

Aftermarket Blocks

If you want to up the ante for increased block strength and/or more displacement, several high-performance blocks are available in the aftermarket for radical street or all-out racing applications. Available in cast iron, cast aluminum, and even billet aluminum, these blocks are designed as an improvement of the factory LS design to accommodate higher-horsepower applications and better withstand the abuse of increased cylinder pressure at higher engine RPM, increased compression, and/or forced induction. Several designs also provide enhanced priority main oiling circuits and improved cooling jacket designs, along with available beefy billet-steel main caps. These aftermarket blocks offer increased durability for higher-demand applications.

Dart LS Next Block

Dart offers an array of LS-based blocks designed to provide superior power, reliability, and durability. In addition to Dart’s offerings of billet-aluminum and cast LS blocks, the company has also introduced its LS Next block, a further evolution of the LS format.

An aftermarket LS block alternative is Dart’s LS Next block, with thicker decks and elimination of the Y-block extended pan rails for crank windage improvements. Full-skirted blocks are also available.

Several performance aftermarket blocks are available, allowing a stronger build for higher cylinder pressure and extended RPM applications. Shown here is Dart’s LS Next block, which features thicker decks, priority main oiling, thicker cylinder walls, and a more-dense high-nickel casting. Similar to design features found in GM LSX race blocks, the decks offer six-bolt-per-cylinder-head fastener locations.

Dart’s LS Next block also features four-bolt steel-billet registered main caps, eliminating the need for main cap side bolts.

The inboard “extra” head fastener locations on the Dart block are smooth-bored, requiring studs that secure to the head deck. The studs pass through the open holes and are secured with shouldered washers and nuts from the valley side.

Some aftermarket LS blocks feature the six-bolt head-bolt design, with extra upper and lower head bolt holes added at each cylinder location, as shown on this Dart LS Next block. Head studs provide added strength.

Dart’s latest block is vastly improved compared to the factory block. It is offered in iron or aluminum; the LS Next block features radical enhancements that include elimination of the factory Y-block skirt for reduced windage and allowing for thicker, stronger full-main web architecture. In addition, the design incorporates extended cylinders that are .375 inch longer at the bottom for better piston skirt support at BDC; low-restriction priority main oiling system; and four-bolt main caps with 7/16-inch bolts. Deck heights are offered in both stock 9.240-inch and optional 9.450-inch sizes to allow displacement increases. Thicker siamesed bores provide for increased oversizing potential for added displacement. Thicker 5/8-inch decks have been added for rigidity. A larger water jacket is installed at the number-1 cylinder, and in the valley is a provision for oil restrictors.

Because the Dart LS Next block’s pan rails have been shortened by 2 inches to improve windage, accommodation is required to mount the oil pan. Choices include a custom pan from Canton or Stefs (these are designed with taller sides) or a pair of spacer rails that mount to the block, effectively regaining the needed mounting surface for the oil pan.

The LS Next block is designed to easily handle 1,500-plus-hp levels when the engine is pushed hard, as in racing conditions. I’ve seen reports of this block in applications pushing past 2,500 hp. These blocks are intended for extreme conditions in motorsports applications. Although I have not built an engine approaching the 2,000-hp level, I certainly view this type of block to be most suitable for extreme power levels, far beyond what a factory stock block could handle. Keep in mind that even the highest-grade block can fail because of problems with other component issues and/or incorrect assembly techniques, such as less-than-robust connecting rods, inadequate valve-to-piston clearance, improperly tightened rod bolts, inadequate bearing clearances, poor oil delivery, etc. But if you want a strong basis for a high-performance build, aftermarket blocks such as the LS Next offer vastly improved strength and durability. Blocks such as these provide a sturdy foundation for extreme power builds. Keep in mind that an engine block unto itself does not make more power; the design and strength incorporated into the block simply allow you to build more power and to better withstand extreme abuse.

With the Moroso 2-inch rail spacers in place, an LS-style oil pan may be mounted. Here a Moroso pan is installed.

Note: A special oil pan is required because of the elimination of the Y-block skirts. Both Canton and Stefs currently offer an appropriate pan, and Moroso carries a dedicated oil pan kit. The Canton and Stefs pans feature 2-inch-taller rails built into the pan design, while the Moroso kit uses 2-inch-thick spacers. This is required to compensate for the 2 inches that were removed from the block’s pan rails.

Dart’s billet LS block is entirely machined from a chunk of high-grade aluminum alloy to finished state on CNC, offering an increase in strength as well as weight reduction. The OEM cast-aluminum bare block weight is about 110 pounds for LS1/LS6/LS3/L92. The weight of Dart’s billet block is about 125 pounds, depending on deck height and bore size. The slight increase in weight compared to the OEM casting is inconsequential, given the billet block’s vastly increased strength. As a reference, the OEM cast-iron LQ9 6.0L block weighs in at about 170 pounds. Shown here is a billet block ready for final cylinder honing to accommodate the builder’s specific piston diameter. (Photo Courtesy Dart Machinery)

Dart’s LS Next MID block features a modular integrated deck design that offers increased cylinder integrity and strength. According to Dart, the distortion is removed from the deck and the sleeves are anchored in compression in the lower block area for enhanced strength. (Photo Courtesy Dart Machinery)

Dart LS Billet Block

One of the many block designs offered by Dart is its billet LS block. The block is machined from a blank chunk of high-grade, aerospace-quality aluminum alloy, offering “virtually unlimited” choices of specifications, including bore centerline, bore diameter, deck height, lifter bore sizes, and cam tunnel height placement. Basically, it’s custom machined to your spec block, offered with either steel or aluminum main caps.

The recently introduced World Products Motown II LS iron block incorporates aftermarket-influenced and enhanced small-block Chevy architecture. It features a 9.240-inch LS deck height with a .134-inch raised cam bore, combining the strength of a performance-upgraded tried and true small-block Chevy with the vastly superior breathing of LS cylinder heads.

Dart LS MID Block

Dart’s LS Next MID block features a modular integrated deck as well as a wet cylinder design to virtually eliminate cylinder distortion from block flexing and harmonics. Cylinder sleeves are seated and anchored in compression in the lower block area where the maximum aluminum mass is concentrated, offering increased cylinder integrity and strength compared to dry sleeves. Compatible with all currently available LS head designs, the Next MID is available in 9.240- and 9.750-inch decks heights and 4.125- to 4.220-inch bore sizes. It requires the use of MLS head gaskets.

World Products Motown II LS Block

This block represents a distinct departure from a typical LS design because the block is essentially a Gen I small-block Chevy design. However, it accepts LS cylinder heads, crankshaft, rods, oil pan, and distributor, but the distributor can be eliminated if you prefer to use a controller and LS coil packs. It also accepts a water pump, crank balancer, oil pump, and other components. The block’s deck height is 9.420 inches with an LS head bolt pattern to allow the use of LS-style heads. The LS-style components include cylinder heads, LS-style pistons, rockers, lifters, and intake manifold.

The most notable design features of the Motown II LS block are the LS cylinder head bolt locations, deck height, and cooling passages.

The lifter bore locations are specific to the LS layout. Bushed lifter bores are standard and must be final-machined to accommodate the lifters of choice. Blocks can be ordered to accommodate either .847- or .904-inch lifters.

The mandatory aluminum valley cover base not only provides a cover for the lifter valley but the angled sides also extend the block’s deck surface to complete the footprint for the LS cylinder heads and feature 5/16-18 threaded holes to accept the heads’ inboard pinch bolts. The base also features a distributor mounting flange to accommodate conventional small-block Chevy distributor mounting. Since the valley cover base completes the deck surface area for the heads, this base must be mounted to the block during final deck surfacing.

The block requires the use of a special camshaft that is essentially a small-block Chevy cam (with distributor drive gear) that features LS cam lobe spacing. The camshaft, which must be custom ordered to meet lift, duration, and LSA requirements, is currently offered by Comp Cams and Erson. Don’t be alarmed at the “custom order” aspect: normal delivery time is only about a week or so. This block design is intended to offer the best of both worlds, combining the easy access and flexibility to accept more affordable tried and true Chevy small-block components with the vastly improved performance of the LS cylinder head designs. A special aluminum valley cover base is available with or without a distributor mounting hole. A separate flat aluminum valley cover plate seals the lifter valley.

One “unusual” aspect of the block is the use of two external coolant hoses that run from each side of the block to a high-mounted water housing. Each side of the block features a threaded water jacket hole that accepts a 1¼-inch NPT male thread fitting that accepts a –12 AN 90-degree hose end. The –12 AN hoses then connect to the coolant fill reservoir that is mounted to the front of the block. The housing features a hose neck for upper radiator connection.

In fact, I recently built a 427-ci engine using one of these blocks. It featured a 4.125-inch bore and 4.000-inch stroke. Components included a Scat 4.000-inch stroker crank, Scat 6.125-inch rods, JE pistons at 1.115-inch compression height, .624-inch-lift Erson hydraulic roller cam, Trick Flow LS CNC heads, Holley single-plane intake manifold and 850-cfm carb, MSD distributor, Fluidampr balancer, Melling oil pump, Moroso pickup and pan, Cloyes timing set, Comp aluminum roller rockers, Trend 7.500-inch pushrods, and ARP main and head stud kits. On the dyno, it easily pulled 641 hp and 555 ft-lbs of torque.

One of the cool features of the block is the motor mount bolt hole locations: both small-block Chevy and LS patterns are built in, allowing an easy swap into any vehicle that was originally intended for a Gen I Chevy or an LS engine.

As is the case with most aftermarket performance blocks, this block is already notched for rod clearance, in this example for a 4.000-inch stroker crank. Additional notch clearancing may be needed for longer strokes.

When ordering a block, options include a choice of either modular or steel-billet main caps. The steel-billet 3, 4, and 5 caps feature splayed outer bolt locations.

RHS Race Block

RHS’s LS Race Block, cast from A357T aluminum alloy and CNC-machined, is intended for all-out race applications. Press-in spun-cast extra-long cylinder bore liners can be finished to 4.125- to 4.165-inch bore diameters. Available in standard LS 9.240- or tall 9.750-inch deck height, the block is designed to accept up to a 4.600-inch stroke and can accommodate up to a 60-mm roller bearing cam. The cam centerline is raised .388 inch to allow for longer stroke. Based on LS7 design, the decks feature a six-bolt-per-cylinder layout with a full water jacket around each cylinder. The block will accept either LS or early generation motor mounts (bellhousing mounts will also accept early or late bellhousings).

BMP LS Block

The Bill Mitchell Products (BMP) LS7X race block is an aluminum four-bolt steel main cap block that features an OEM main bore (to accept any LS crank). Deck height choices include standard LS 9.240 inches or 9.800 inches. Cylinder bores are available in 4.000 inches and can accept up to 4.185 inches. Other features include priority main oiling, LS and Gen I motor mount locations, billet-steel main caps, cam bores that can be machined to 60 mm, and six-bolt-per-cylinder-head bolt locations. The block will readily accept crank strokes up to 4.250 inches.

As a convenience feature, both small-block Chevy and LS motor mount bolt holes are provided, making it easy to install this block in an early vehicle that originally had a small-block Chevy engine or a later vehicle that was equipped with an LS engine; no custom motor mounts are needed.

RHS offers its LS Race Block, a cast-aluminum block that is fully CNC-machined, intended for racing applications. Considering optional raised-deck versions and the ability to accommodate as much as a 4.600-inch stroke and 4.165-inch cylinder bores, these blocks are capable of 500-plus ci of displacement and are designed to withstand an estimated output of 2,000 hp. (Photo Courtesy Racing Head Service)

The BMP LS block is cast aluminum and will accommodate up to a 4.185-inch bore and 4.250-inch stroke. The block has many unique features that support max-performance builds. The main caps are 1045 steel alloy rather than 1020. The block has priority oiling that lubricates the crankshaft mains first and the top end second. (Photo Courtesy BMP)