ATK Engines HP99C GM Chevy Vortec 350 Complete Crate Engine 290HP

ATK's HP99C is a complete, bolt-in Chevy 350 Vortec build at 290 hp and 375 lb-ft of torque, aimed at bringing a tired small block back to dependable service rather than chasing stroker-level output. The 2-bolt main OE block keeps this engine in familiar territory for a factory-style rebuild.

What ships installed

Because this is ATK's complete tier, nothing on the induction or ignition side is left for the installer: the intake, distributor, water pump, and balancer are mounted, the carburetor is bolted to that intake, and a flexplate or flywheel ships to match your transmission. Vortec cast-iron heads give the valves a 1.94/1.50 opening, and hypereutectic pistons run 9.4:1 compression under a hydraulic roller cam.

Before you order, check this

• This engine has no provision for a mechanical fuel pump; it must run on an electric pump instead.
• Oil pump is a standard-volume Melling unit paired with a rear-sump oil pan.
• A single-roller timing chain is matched to this block's bore and stroke.

Common questions

Is the carburetor already on the engine? Yes, a vacuum-secondary carburetor with an electric choke is already mounted on this complete build.

Can I run a mechanical fuel pump? No, there is no mechanical pump provision; plan on an electric pump.

What's the compression ratio? 9.4:1, built for dependable street use rather than peak output. California requires BAR compliance for engine swap installations.