The all-aluminum LS1 was a completely new design and shared virtually nothing with earlier
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 LS series is unique in many ways; note the tall intake port and the evenly spaced exha
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.
GM Performance Parts offers this complete LS1 engine assembly (PN 1780).
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).
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