Throughout the earliest years of Corvette design and development, a definite trend began to emerge. In almost every case, famed GM engineer, Zora Arkus-Duntov, would always find a way to ring every last ounce of horsepower out of an engine. Ever the perfectionist, Duntov relentlessly sought out new and innovative ways to bolster the Corvette’s output, in a bid for performance superiority.
There are perhaps few greater examples of Duntov’s ideology relating to engine design and development, than the 1970 LT-1 small-block. The LT-1 served as a revised version of GM’s famed 350 cubic-inch platform and is often heralded as one of the manufacturer’s most beloved small-block powerplants. With 370 horsepower on tap, it is not difficult to imagine why.
The early 1970s were harrowing days for many automotive manufacturers. The horsepower wars of the 1960s continued, though increasing federal oversight began restricting that which was permissible in regards to emissions. Government agencies had established environmental mandates, which threatened to limit available powerplant options, in a bid to reach compliance.
This is a fact that was not lost upon Arkus-Duntov and his associates, as they recognized that increasingly stringent emissions standards would ultimately slow subsequent performance-related gains. In fact, the detuning of many General Motors’ passenger vehicles had already begun.
In order for the manufacturing giant to retain some level of performance dignity, the Corvette would have to have a strong showing during the 1970 model year. While the prior 427 big-block was bored to a full 454 cubic-inches, perhaps the most significant powerplant related development in 1970 came with the introduction of the LT-1 small-block.
The LT-1 served as a high-output version of GM’s famed 350 cubic-inch engine platform. With a revised crankshaft, redesigned pistons, and a higher compression ratio, the LT-1 took on a life all its own and gained instant notoriety for its profound performance.
LT-1 Specifications and Technical Configurations
Much of the LT-1’s promise lied in its internal construction. This engine utilized a cast-iron cylinder block, which housed a 1018 alloy-steel crankshaft. This crankshaft was cross-drilled, as well as internally balanced, and featured Moraine 400 rod and main bearings.
The LT-1’s connecting rods were of a heavy-duty ⅜” bolt configuration and measured 5.700” in length while weighing just under 21-ounces a piece. Opposite the crankshaft, these connecting rods supported specialized forged TRW pistons, of a high silicone aluminum construction. Each piston was secured with the use of pressed chromium-steel wrist pins.
The pistons used by the LT-1 were of a slipper-skirt design and featured similar piston rings to those found on other engines within the 350ci small-block family. The first of these rings was of a cast-iron construction, complete with a molybdenum inlay. The second ring featured an inside bevel, and consisted of ductile iron, while the LT-1’s oil control ring was of a chromed steel build.
A solid-lifter camshaft was featured in the LT-1, which supported .4586” of intake lift and .4580” of exhaust lift. The engine’s intake valves opened at 38 degrees before top dead center, and closed at 94 degrees after bottom dead center. Likewise, the LT-1’s exhaust valves opened at 86 degrees before bottom dead center, and closed at 46 degrees after top dead center.
The LT-1 featured a set of proprietary aluminum heads, which were minimally restrictive and conductive to streamlined induction. These heads were fitted with sizable intake and exhaust valves (2.02” intake, 1.60” exhaust).
Atop the LT-1’s heads sat a specialty Winter aluminum intake manifold. This manifold was of high-rise, dual-plane configuration, and featured a divided plenum. Affixed to the LT-1’s intake was an 800-cfm Holley carburetor, which included racing-spec fuel bowls and center-hung floats.
LT-1 Specs Index
Horsepower: 470 hp @ 6,000 rpm
Torque: 480 lb./ft. @ 4,000 rpm
Compression Ratio: 11.0:1
Displacement: 350 cubic inches ( 5.7L)
Cylinder Bore: 4.065 inches (103.251 mm)
Stroke: 3.62 inches (92mm)
Vehicles Using the LT-1 Engine
Though quite legendary in status during the modern era, the LT-1 was rather obscure and short-lived during its production run. The LT-1 was only produced for three years (1970-1972), before being retired by General Motors, presumably because of concerns toward increasingly stringent emissions standards.
During its production run, the LT-1 was only used in the Chevrolet Corvette and Camaro, with the latter being rated at 10 horsepower less than that which was found beneath the Corvette’s hood. In total, only 1,287 LT-1 Corvettes were sold during the 1970 model year.
A Legendary Small-Block
Today, the LT-1 is remembered as one of GM’s most renowned small-block creations. The storied powerplant dished out a substantial amount of horsepower and responded willfully to even the most modest of jabs at the accelerator. In short, it is difficult to imagine anyone not enjoying their time behind the wheel of an LT-1 equipped Corvette.