The LT4 was a special high-performance version of the LT1, a two-valve, pushrod 350-cubic inch V8 engine manufactured by General Motors. While the LT1 was utilized in a variety of Cadillac, Chevy, Pontiac and Buick models, the LT4 was only offered from 1996 and 1997 in special high-performance variants of the Corvette, Camaro and Firebird. The LT1 and LT4 were supplanted by the LS1 from 1998 onward.
Design of the LT4
The LT4 was an iron block, two-valve pushrod V8 similar to the LT1 upon which it was based. The LT4 improved upon the anemic top-end power of the LT1 by replacing certain head components to improve higher RPM performance. This included a high-profile camshaft, aluminum roller arms, high-flow cylinder heads and a port-matched intake manifold. These modifications resulted in an increase of 30 horsepower from 300 hp to 330 hp, while maintaining a torque rating of 340 hp. Peak torque was achieved at 4,500 rpm, as opposed to 4,000 rpm for the LT1.
The LT4 was offered as the standard engine in all manual transmission-equipped 1996 Corvettes, the last year of the C4 design. In addition to the Corvette, the LT4 was offered in the 1997 Camaro SLP SS and the 1997 Pontiac Firebird SLP Firehawk.
Upgrading a LT1 into a LT4
Since the LT4 consists of revised heads with no modifications to the bottom end, you can upgrade a LT1 into a LT4 by purchasing a LT4 hotcam which is offered by General Motors Performance Parts. Note you will need to tune the engine to account for the revised camshaft.
Replacement of LT1 and LT4 by the LS1
The LS1 was a clean sheet design which replaced the LT1 and LT4 engines from 1997 forward through 2007. The LS1 contained a host of features including an aluminum block and coil-on-plug ignition. The LS1 also addressed the LT1's anemic high-end power and came in a variety of variants.
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