The small-block Chevy is arguably the most popular performance engine of all time. When the 265 Chevy V-8 came on the scene in ’55, it was revolutionary and over the years it just got better. But despite all the changes the good old small-block Chevy remained a known commodity; so even though building a Custom Classic Truck is often about incorporating the latest technology in an older vehicle there was something comforting about the small-block Chevy. It looked pretty much the same over the years, parts were plentiful and cheap, but perhaps most of all it was a constant in an automotive world that was continually changing.

Although the little Bow Tie is a remarkable engine, the fact is since it first appeared there have been a number of advancements in engine technology as exemplified by General Motors’ Gen III and IV series of engines.

The first engine in the Gen III series was the LS1, which featured a bore of 3.897 inches and a stroke of 3.662 inches, resulting in a displacement of 345.69 cubic inches; however, Chevrolet called it a 350, or a 5.7L engine. Based on an aluminum block that weighed a scant 107 pounds, thanks to the deep skirt design and six-bolt main caps, it was every bit as rigid as its 160-pound cast-iron predecessor. Also found inside the block were cast-iron liners, a new, shorter nodular iron crankshaft, and powdered metal rods. While the curmudgeons among us scoff at the thought of connecting rods being made in a manner reminiscent of baking a cake, the truth is, these are the strongest rods ever to find their way inside a production GM engine.

The LS1 architecture is considerably different to those familiar with the traditional small-block Chevy. Some of the most obvious differences are up top. Cast from 356 aluminum and heat-treated to T6 specs, the new heads have a long list of advantages over previous designs. Upon close inspection, one of the most obvious is that all the intake ports are all identical, as are the exhausts, which simply means that all cylinders breathe equally well. Less obvious differences in the new heads are the valve angles. It’s generally agreed that the shallower the valve angles the better. The LS1 valves are at a 15-degree angle, considerably less than the earlier small-block’s 23 degrees. But one of the LS head’s most important attributes is the location of the fuel injectors. As these heads were designed for fuel injection rather than retrofit with it, the injector’s fuel streams are aimed directly at the back of the intake valves.

Like most contemporary engines, the LS1 uses roller lifters as well as investment cast roller rockers. But one of the pieces that makes old-timers do a double take is the “plastic” intake manifold. Frankly, the common lament that those manifolds won’t be around in 75 years like a Flathead Ford’s makes us want to point out that neither will we. The fact is, making the manifold from composite material allows for the curved runner configuration, plus it’s light and cost effective. Another unique feature found on the manifold is the fly-by-wire throttle body. The LS1 was the first GM car to use a computer-controlled throttle (light-duty diesel trucks began using them in ’95).

Of all the features of the LS1 that are out of the ordinary, the most obvious are the rocker cover-mounted coil assemblies. Each cylinder has its own coil and coil driver assembly with a short secondary wire connecting to each spark plug. The reasons given for moving the coils to the covers were the shorter plug wires lost less energy, so more was delivered to the plug as well as reduced radio frequency interference with on-board computers. A less noticeable feature is the change in firing order; no longer using the familiar 1-8-4-3-6-5-7-2 sequence, new engines fire 1-8-7-2-6-5-4-3.

With all that is unique on the LS1, one of the pieces that almost escapes notice is the oil pan, but there’s more to it than meets the eye. There have been a half-dozen or more cast-aluminum pans used on theses engines; the Corvette, or batwing pan, is a two-piece and has two wings to the sides, and the Camaro and Firebird pans have a shallow rear sump. But no matter what the shape is, in all cases the pan becomes a part of the engine’s structure when screwed in place and contributes to the block’s rigidity. Another unique feature is these pans also provide a mount for the oil filter.

Family Tree

General Motors’ new engines can be broken down into two series: Generation III and Generation IV. They share the same features and attributes in most respects.

Gen III blocks were made from cast iron in 4.8, 5.3, and 6.0L sizes (used primarily in trucks) and aluminum for 5.3, 5.7, and 6.0L. While iron blocks are heavier, they can easily be bored oversize during a rebuild; the aluminum blocks shouldn’t be bored more than .010-inch according to GM.

As we said, there are various versions of the Gen III, but the following are most sought after:

LS1: The 5.7L LS1 was the first in the Gen III series. The engine was used in the ’97 Corvette C5 and was later found in the Camaro, Firebird, and GTO. Horsepower varied from 305 to 350 depending on the application. A cast-iron version of this engine appeared in trucks in 1999.

LS6: Debuting in the C5 Z06 Corvette in 2001, this engine was an enhanced version of the LS1. The block was improved, the intake manifold modified, the cam was more aggressive, and compression was increased. While the displacement remained the same, the LS6 produced 385 hp when introduced, and it was cranking out 405 ponies by 2002.

While these engines were also found in the Cadillac CTS V-series, some may remember the ’70s when the original LS6 was a 454ci big-block.

Gen IV

These engines were introduced in 2005 and were designed to accept GM’s “displacement on demand,” or DOD technology. A new lifter oil manifold was included, the cam sprocket was redesigned, a higher-volume oil pump was used, and the oil galleys were modified. For our purposes, the benefit is these blocks will accept a larger bore.

LS2: Gen IV engines introduced the big-bore versions of the LS series. The 6.0L LS2 was the new base engine for the Corvette beginning in 2005. With a 4-inch bore and a 3.62 stroke displacement, it comes out to 364 cubic inches. Compression was 10.9:1 and it was rated at 400 horses with 400 lb-ft of torque. In addition to Corvettes, these engines were also found in Cadillac CTS-Vs, Chevrolet SSRs, and the TrailBlazer SS.

LS3: Introduced as the new base engine for the 2008 Vette and is based on a modified LS2 block. A bigger 4.06-inch bore results in 6.2L, or 376 cubic inches. High-flow heads, a bigger cam, an improved intake manifold, and larger injectors result in 430 hp with 424 lb-ft of torque.

LS7: Found in the 2006 Corvette Z06, the LS7 has a 4.125-inch bore and a 4.125-inch stroke that results in 7.0L/427 cubic inches. Horsepower is 505 at 6,300 rpm, torque is 470 lb-ft at 4,800 rpm, and the redline is at 7,000 rpm. Inside, the aluminum block is some tough stuff-the crankshaft and main bearing caps are forged steel, connecting rods are forged titanium, and the pistons are hypereutectic. The LS7 features a dry-sump lubrication system.

LS9: This astonishing engine is the ZR1 Corvette 6.2L asphalt shredder. Super charged and equipped with a dry sump oiling system, it pumps out 638 hp at 6,500 rpm and 604 lb-ft torque at 3,800 rpm.

The LSX-Series: Chevrolet introduced these engines for one purpose, maximum performance. The LSX is described as “boost ready” and the LSX454 can be configured with fuel injection or a carburetor.

What It Takes to Join the New Generation

Installing a computer-controlled engine in a street truck has become just as easy as any other engine swap. Look no further than our advertisers index at the back of the magazine or the list below (for LS-related components) to find everything you need, including complete engines, computers, wiring harnesses, throttle bodies, headers, and all the other little doodads necessary. However, there is one little oddity that you should be aware of if you’re contemplating a Gen III or IV engine installation: the positions of the cooling systems inlet and outlets. They stick straight out and may require some clever plumbing so as not to use up valuable under-hood space in an early truck. CCT

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