The cylinder block is the foundation the rest of the engine is built upon. If incredibly high horsepower, torque, and RPM are the goal, the needs may surpass the capabilities of even the best factory offerings.
This Tech Tip is From the Full Book, HIGH-PERFORMANCE GM LS-SERIES CYLINDER HEAD GUIDE. For a comprehensive guide on this entire subject you can visit this link:
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This chapter briefly reviews factory and aftermarket offerings, providing the basic engineering and capabilities. While all LS blocks are impressive when compared to vintage designs, the important thing to today’s LS enthusiasts is what their block is capable of, or what block they need to reliably handle their target power level. That information is here, so you know what you have or what you need.
By now you know that it all began with the LS1, a block that was cast of 319-T5 aluminum with centrifugally cast iron cylinder liners. Although by today’s standards an aluminum block is common, in 1996 few production vehicles had them, let alone one as mass-produced as the LS1 (in both the Corvette and then the Camaro and Firebird a year later). The added cost and questionable durability of cylinder coatings such as Nikasil, needed for proper ring seal and resistance to wear and distortion, made aluminum blocks undesirable for OEMs. However, by casting the iron liners in place with the block, GM was able to create a reliable method with little weight penalty. As a result, the LS1 block weighs a svelte 107 pounds; its iron-block cousins weigh an additional 88 pounds.
The LS1 block design has many features that help make it superior to its predecessors and capable of handling plenty of power. The overall design is robust; it’s a deep-skirted block with (iron) six-bolt mains and extra ribbing in critical areas (designed with finite element analysis, or FEA, modeling). These features are found throughout all LS blocks, as well as the standard small-block Chevy 4.400-inch bore spacing and a 9.240-inch deck height. But all blocks were not created equal; bore diameter, cylinder length, head bolts, and oiling are just a few of the variations.
The original aluminum LS1 block used in 1997–1998 Corvettes and the 1998 Camaro and Firebird (casting # 102550592) is thought to be the least desirable of all variations. The cylinder liners are particularly thin, and can only tolerate a light hone (.005 inch) during a rebuild (the later blocks allow .010 inch). The early blocks also have a disadvantage in the oiling department, which makes them easy to spot if bare and on a shop floor. Two small holes make up the rear oil passage above the cam instead of the later blocks’ open passage.
The early blocks and the 1998–2000 version (casting # 12559846, 12559090) utilize what is characterized as “medium-length” head bolts, in contrast to the 2000–2002 LS1 (casting # 12559378, 12560626) and 2001–2004 LS6 (casting # 12564243), which have longer head bolts. Neither is said to be an advantage or disadvantage.
The LS6 block boasts the best bay-to-bay crankcase breathing of the bunch. Rather than small machined holes, bulkhead windows were cast in place to more effectively relieve crankcase pressure, which escalates at higher RPM. As a result, most racers and hot rodders installing big cams prefer this among all the 3.89-inch-bore aluminum blocks. All of the above are fairly plentiful used, though new LS6 blocks are still available for $990. Gen III truck blocks share many of the nuances of their cousins with two critical differences: All but one is made of iron and they have different bore sizes. The 1998–2004 (casting # 12551358) and 2002–2004 (casting # 12567392, 12567393) block used in the 4.8- and 5.3-liter LR4, LM7, and L59 utilize a 3.779-inch-bore iron-block. The 5.3 LM4 (casting # 12566910), as well as its current Gen IV counterparts, the LS4 (casting # 12569004) and LH6/LC9/L33 (casting # 12572733), were the few to be made of aluminum because of cost and NVH (noise vibration harshness) issues. These blocks were given the updated LS6 design.
The 4.8/5.3 blocks have become a hot rodder’s dream, as they are plentiful in many boneyards and quite cheap. The aluminum versions are more rare, and therefore costly. They can be bored out to the standard 3.89-inch bore for a 327- or 346-ci monster.
It should be noted that the LS4 was designed for a front-wheel-drive application, is the most rare, and is not desirable because of the casting differences, which only make it useful for a front-wheel-drive or rear-engine trans-axle setup.
Historically, the 6.0 iron block has been a formidable basis for serious horsepower as well as budget strokers. Mike Moran’s tube-chassis Camaro became the first LS1 to run 6s in the quarter-mile prior to the availability of aftermarket blocks, thanks to its 6.0 truck-block-based, twin-turbo combination built by Wheel 2 Wheel Powertrain.
When the 1998–2004 LQ4 block (casting # 12551364) was first designed it was done the most economic way possible, by transposing the LS1 design to a 4.00-inch bore, iron-block version. As a result, these blocks are perhaps overly reinforced (and heavy), which makes them great for forced-induction builds. The cylinders abide by a traditional .030-inch bore and hone, and with machining can accept aftermarket 1/2-inch head studs for better clamping. Best of all, the cylinder length and large bore make it extremely rewarding to use a longer stroke crank (such as a 4.00-inch for a square motor). These engines and blocks are also fairly common in junk-yards and cheap (though not quite as cheap as a 4.8/5.3), though they are also still in production in the L96 (Silverado/Sierra HD) and cost $773.
The Gen IV block production kicked off with the LS2 (2005–2009), which utilized the same bore and stroke as the 6.0 truck engine except it had an aluminum block with iron cylinder liners like the LS6 and similar internal structure. A few notable differences between the LS2 (casting # 12568950) and the LS6 include provisions for active fuel management, or displacement on demand, and a set of lifter towers located in the valley, which necessitated moving the knock sensor to the (left) outside of the block. The relocation of the knock sensors as well as the cam sensor (to the front timing cover), must be accounted for with the wiring harness. The plastic lifter trays on the LS2 are also unique to Gen IV blocks, but are also reverse-compatible with Gen III blocks (Gen III lifter trays do not work in Gen IV blocks).
Like the truck block, the LS2 responds really well to 4.00-inch-stroke cranks, allowing 402 ci or more at a price that won’t break the bank. No more than a .020-inch hone is recommended. New blocks cost around $1,100 and are still in production thanks to various other engines such as the L76 and LZ1 hybrid. A healthy production run also means they are fairly abundant used.
A year after the LS2 debuted in the sixth-generation Corvette, the 7.0 LS7 upstaged it in the Corvette’s Z06 model. In many ways the LS7 was a stop-gap between the LS2 and the C5R block developed for the GM Racing program. The LS7 has Siamesed cylinders (like the C5R) with pressed-in 4.125-inch-diameter iron liners. The large bore and extra-long cylinders were designed specifically for a 427-ci combination to withstand the heat of road racing. An improved water jacket for better thermal balance and an oiling system that better feeds the bearings and lifters, plus chilled bulkheads, help give the engine longevity.
This block is capable of up to a 4.125-inch stroke, though only a light hone (.005 inch) is possible with the necessarily thin liners. The only knock on this block is that its liners are not durable enough for substantial boost and can easily crack with detonation.
The LS7 brought about many improvements to the machining, casting, and production methods used by GM. The next evolution in the Gen IV design, which benefitted from this substantially, was the 6.2 L92 and LS3 block (casting # 12584727). By increasing the bore size to 4.065 inches, GM was able to provide less shrouding for the massive valves in its revolutionary new heads. The thick cylinder liners allow for a .020-inch bore increase, and these blocks have proven to be very durable.
The LSA block used in the supercharged 6.2 Cadillac CTS-V (2009+) and Camaro ZL1 (2012+) take the LS3 design a bit further by adding piston oil squirters, which help cool the pistons for better durability and to reduce detonation. The LS9 (casting # 12621983) also uses this technology, necessary for factory durability standards in a 638-hp supercharged engine. The LS9, developed for the 2009 Corvette ZR1 supercar, is by far the strongest OEM block and a great candidate for a high-horse boosted application. Like its heads, strength was a concern, so the bulkhead windows were redesigned (to also improve breathing) and the standard powdered metal main caps, used in all LS blocks, were substituted for forged steel. Last but not least, the head bolt provisions went from 11 mm to 12 mm for better clamping. The improvements, though, come at a premium—a $3,800 price tag. The LS3/L92 is only $1,435 and the LSA is priced between them at $2,538.
It should come as no surprise that since day one, the aftermarket has been looking for ways to build a larger-cubic-inch LS1. At its initial release, there was little choice but to develop a method for resleeving the factory cylinders. Many attempts were made with varying degrees of success. However, Darton was one of the first to develop some reliable methods, which have since been perfected by the likes of shops such as Race Engine Development (RED).
The premise is simple: The cylinders are bored (as you would a normal engine), which removes the iron liners and the aluminum cylinder wall. Next, the Darton ductile iron liners, which are much stronger than the factory centrifugal cast iron units, are installed. With Gen III blocks, where there is a coolant passage between the cylinders this process gets a bit tricky. The Darton Modular Integrated Deck (MID) liner system solves past issues with resleeving by integrating each sleeve yet still encircling the liners with coolant (known as a wet sleeve). Bore sizes are available for 4.125 to 4.160 inches and 4.170 to 4.200 inches.
The Gen IV blocks, by comparison, may utilize either the wet MID sleeves or the more economical dry sleeves to obtain larger bore sizes. With the dry sleeves, the process of removing the old cylinder liners is not much different. However, the machine work and labor involved in installing the new sleeves is much less extensive (read expensive). The LS7 in particular is a great candidate for dry sleeves such as Darton’s Seal Tight, which has a phosphate coating, cooling fins, and boasts triple the strength of the factory liners.
There are a surprisingly large number of LS7 blocks left for dead with cracked liners and even cylinder walls as the result of detonation, and could easily be brought back to life and made stronger than ever with Darton sleeves. All Darton LS sleeves boast 5.800 inches of length, too, making them more suitable for stroker cranks. RED charges $2,650 for MID installation (ready for finish hone), and $1,845 for dry-sleeve installations.
Since the development of aftermarket blocks, particularly those that are more cost effective than the C5R and/or made of aluminum, resleeving Gen III and IV blocks has become less common. However, there are still plenty making as much as 2,000 hp with factory-based blocks thanks to ERL Performance and its Superdeck I. ERL takes Darton’s and RED’s efforts a step further by welding in aluminum trusses (with coolant holes) that connect each pair of head bolts to spread the clamping load across the deck surface to prevent distortion.
After ERL is finished with its internal strengthening, it uses similar ductile iron sleeves to increase strength and wall thickness. ERL also has the ability to machine for 1/2-inch head studs and add two more head bolts per cylinder (like an aftermarket block). In this variation, billet steel main caps are also used, which make the engine capable of 1,500 hp (for $3,500 not including core). ERL also makes a main girdle for an additional $500. The basic Superdeck I starts at $2,900. Dry-sleeved blocks are also available ($2,250), as are Superdeck II short-blocks, which integrate a deck plate extension into the sleeves to allow a 4.500-inch-stroke crank (and up to 500ci).
The capability for larger displacement and withstanding higher cylinder pressure makes aftermarket blocks particularly appealing.
The Chevrolet Performance LSX block is easily the most recognizable and affordable aftermarket block. However, it certainly is not the first. It all began with the C5R, which is still in production and available today. This heavy-duty aluminum race block was designed for dry sump oiling systems, large cubic inches, and plenty of abuse. It was the first LS engine to have a large bore (4.125 inches), which can even be increased by .035 inch for rebuilds. It was also the first block to have Siamesed cylinders, and GM even out-fitted it with billet steel main caps. These blocks still command a $6,980 price, which created a large demand for the more affordable, ironclad LSX block ($2,665). The use of iron not only keeps the cost down, but it boasts excellent rigidity and with-stands extremely high cylinder pressure. Increased clamping force is also achieved due to the six head bolts per cylinder.
Legendary NHRA racer Warren Johnson helped develop the LSX block, perhaps that’s where its priority main oiling came from. The maximum bore is a whopping 4.250 inches, though most stay safely around 4.185 inches, and longer cylinders allow for up to a 4.200-inch stroke. GM’s encore to the standard, 9.26-inch-deck LSX block was a tall-deck (9.70-inch) version to allow a 4.350-inch-stroke crank (or more). Some of the fastest LS-powered cars in the world use LSX blocks as their foundation.
The World Products Warhawk debuted around the same time as the LSX block, except it is modeled more off the C5R and cast from 357-T6 aluminum (the strongest alloy available). The sleeves are .100-inch thick and backed by more than .300 inch of aluminum (compared to the C5R’s .070-inch-thick sleeve and .170-inch support). The Warhawk’s main caps are made from billet 1045 alloy steel, and it also has priority main oiling. Six bolts per cylinder (and a .600-inch-thick deck) clamp the cylinder head better than the C5R and OEM blocks, though it is worth noting the pattern is slightly different than the LSX and RHS blocks.
The extra-long sleeves accommodate up to a 4.250-inch-stroke crank, for up to 454 ci. Maximum bore size is 4.155 inches. The standard deck (9.24 inches) retails at $4,700, and the tall-deck (9.800 inches) commands $5,690. The ability to add a 4.500-inch-stroke crank makes near 500 ci a reality.
Dart Machinery was next to introduce its billet aluminum block. This block has the most potential. Because it is a billet block, pretty much anything can be changed (deck height, cam height, bore spacing, cam journal, etc.). It offers the light weight of aluminum, but with uncompromising strength. Dart chose forged 6061 aerospace alloy with a proprietary heat treatment as the basis for creating a maximum-effort bullet that is seven times stronger than its cast counterpart, and then added billet steel main caps.
Virtually every potential issue can be solved with Dart’s billet block, from core shift to cam interference and bore or stroke limitations. Racers enjoy the custom-spec head-bolt pattern and sizing, full or uncut water jacket, ability to do a 60-mm cam tunnel, custom lifter diameters, and ability to raise the cam journal in taller deck configurations. Expect to pay a minimum of $8,000.
Racing Head Service
Some will certainly argue that the best was saved for last. Racing Head Service’s LS Race Block is somewhat of a deceptive name since it is easily as at home on the street as it is on the track. Cast from A357-T6 aluminum, it uses press-in spun cast-iron cylinder liners and has a .500-inch-thick deck. The water jacket also bears resemblance to the LS7, with Siamesed bores; however its extra-long sleeves and six-head-bolt provisions help give it a significant edge. The cam tunnel can house a standard or 60-mm roller bearing camshaft, and there is extra material in the lifter bore and around the head bolts for larger-than-standard sizes. The lifter area has also been opened up to permit removal of the lifters without removing the heads. Provision for dry sump lubrication is also one of many great features (too many to list).
The RHS block is available in standard-deck (9.240 and 9.250 inches) and tall-deck (9.750 and 9.760 inches). Tall-deck versions have a raised camshaft tunnel (.388 inch), which increases rod clearance with the longer crankshaft stroke. These blocks are available unfinished or bored and ready to hone for $4,977. Those completely machined are ready to put together for $5,082.
Written by Dave Grasso and Posted with Permission of CarTechBooks
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