The first LT-1 (with a hyphen) engine was introduced in the Corvette in 1970 as an option. It was a raucous, racing-inspired engine with solid valve lifters, a high-lift camshaft, and high-winding personality that redefined small-block performance. Displacing 350 ci (5.7-liter) with a compression ratio of 11:1, it was rated at 370 hp at 6,000 rpm and 380 lb-ft of torque at 4,000 rpm. It was enough to push the Corvette from 0-to-60 mph in less than 6 seconds.
Indeed, the LT-1 was a true high-performance powerhouse, featuring many heavy-duty components not found on the Corvette’s standard 350 engine, including a stronger cylinder block with four-bolt main caps, forged aluminum pistons, a high-rise aluminum intake manifold, a baffled oil pan for reduced windage, a transistorized ignition system, and high-volume oil and fuel pumps.
Only 1,287 Corvettes left the factory in 1970 with the LT-1 engine. It remained in production for another couple of years, but lower compression ratios and other regulations-conforming changes resulted in lower horsepower.
The LT1 (no hyphen) returned to the Corvette in 1992, launching the five-year lifespan of the Gen 2 small-block. It built on the successful design of the L98-code Gen I small-block that debuted in 1985, featuring the port fuel injection design that most automotive engines still use today. Like the original LT-1, the Gen 2 version displaced 350 ci and featured a four-bolt main block.
The Gen 2 LT1’s most significant update over the Gen I small-block was a reverse-flow cooling system, which cooled the cylinder heads first to achieve lower cylinder temperatures. That allowed a higher, 10.4:1 compression ratio that helped achieve greater power: 300 hp at 5,000 rpm and 330 lb-ft of torque at 4,000 rpm. It helped the Corvette achieve 0-to-60 acceleration comparable to the 1970 model, while also helping propel the 1992 model to a top speed of more than 160 mph.
To mark the final year for the C4 Corvette generation and the final year for the Gen 2 small-block, a pair of special-edition models was offered in 1996 with a higher-power version of the engine, dubbed LT4. It was rated at 330 hp and is easily identified by its red cast-aluminum intake manifold.
After an 18-year hiatus, the LT1 returned to the Corvette for 2014, matching an all-new car with an all-new Gen 5 engine-one of the most technically advanced engines in the world and the most significant redesign of the small-block ever. It will have the highest base horsepower and torque, as well as the greatest efficiency of any Corvette in its 60-year history.
|LT1 engines compared|
|1970 LT-1 (Gen 1)||1992 LT1 (Gen 2)||2014 LT1 (Gen 5)|
|Displacement||350 (5.7L)||350 (5.7L)||376 (6.2L)|
|Bore x Stroke (inches)||4.00 x 3.48||4.00 x 3.48||4.06 x 3.62|
|Cylinder block||cast iron||cast iron||cast aluminum|
|Main bearing cap fasteners||four||four||six|
|Cylinder heads||cast iron||cast aluminum||cast aluminum|
|Valve sizes (intake / exhaust)||2.02 / 1.60 inches||1.94 / 1.50 inches||2.13 / 1.59 inches|
|Camshaft type||solid lifter||hydraulic||hydraulic|
|Fuel delivery||four-barrel carburetor||port fuel injection||direct injection|
|Ignition||transistorized with cam-driven distributor||“Optispark” optically triggered distributor||individual coil-on-plug|
|Horsepower||370 at 6,000 rpm||300 at 5,000 rpm||450 (estimated)|
This is the 1970 Chevrolet 350ci LT-1 as it was offered in Corvettes. It featured an aggressive solid-lifter cam and a single four-barrel carburetor.
The LT1 introduced in 1992 was unique for a number of reasons, not the least of which was the reverse-flow cooling system and direct drive water pump.
The all-aluminum 2014 LT1 had the largest displacement of the trio and was the first to feature direct fuel injection.