ATK HP57 Chevy 350 Base Engine 1987-1991 Corvette

The HP57 is a direct-fit long block built for 1987-1991 Corvettes, tuned to idle smoothly and drive like the engine it replaces. It is rated at 289 hp and 370 lb-ft of torque, and it keeps the factory-style TPI intake arrangement so the original fuel delivery carries over onto the new long block.

What is under the dress

Aluminum Performer-style heads sit over hypereutectic pistons at 10:1 compression, run by a hydraulic roller camshaft and stamped-steel 1.6-ratio rocker arms. The 350-cubic-inch displacement comes from a 4.040-inch bore paired with a 3.480-inch stroke. ATK builds this on a later-generation roller-block core rather than the original two-piece-seal design, a detail worth knowing if you ever cross-reference part numbers against a factory engine.

Fitment note before you order

A standard small-block oil pan ships with this engine, and ATK notes it may not clear every Corvette chassis; where it does not fit, plan to reuse your original pan rather than force the new one. Recommended fuel is 91 octane or higher, and keeping the stock-style intake means your factory wiring and sensors should carry over with less fuss than an aftermarket induction swap would require.

Q: Will this bolt in like the original engine? It is built as a performance replacement for 1987-1991 Corvettes with daily-driver manners.

Q: Do I need a new oil pan? Only if the standard pan included does not clear your particular car; otherwise keep your factory pan on hand.