ATK LM7/LS1 GM 383ci 515 HP LM7-LB-3 Stage 1 Long Block Crate Engine

Description

Experience unrelenting high-RPM stroker acceleration through the ATK LM7-LB-3 Crate Engine in Stage 1 long block configuration. Displacing 383 cubic inches, this small-block GM stroker produces 515 horsepower at 6,200 RPM and 490 lb-ft torque at 4,800 RPM. Built on a rigid iron block, it delivers massive low-end torque and high-RPM power for serious performance enthusiasts.

A sonic-tested cast iron LM7 block is clearanced for stroker counterweights and anchored with cross-bolted 6-bolt main caps. The rotating group features a 4340 forged steel 4.000-inch stroke crankshaft, 6.125-inch 4340 forged H-beam rods, and 10.5:1 forged pistons inside 3.903-inch bores. An internal neutral balance design joins an oil-baffled pan for total crankcase fluid control under heavy acceleration.

Key Features of ATK LM7-LB-3

Drag racers buy ATK LM7-LB-3 crate engine models to obtain reliable LS stroker displacement without purchasing expensive aftermarket blocks. This stroker long block repowers vintage muscle cars, GM trucks, and competition bracket sedans.

• CNC-machined aluminum cylinder heads drop front suspension weight while flowing massive air charges at elevated RPM.
• 2.02-inch intake and 1.60-inch exhaust valves maximize cylinder fill efficiency for fierce stroker torque production.
• 0.600-inch lift hydraulic roller camshaft opens valves rapidly while maintaining valvetrain stability at sustained high speeds.
• 232-degree intake duration at 0.050-inch lift profiles the engine for broad mid-range and top-end track acceleration.
• 1.7:1 ratio roller rockers transfer cam lift without pushrod deflection under high valve spring tension.
• ATK LM7-LB-3 stroker packages feature internal engine balancing to eliminate external counterweight vibrations across the entire powerband.
• Double-roller billet timing gear set locks in precise camshaft degree alignment across prolonged race weekends.
• Baffled oil pan configuration keeps lubricant centered around the oil pickup during sudden standing-start acceleration.

Dyno Profile Valvetrain Behavior

Dynamometer testing confirms 515 horsepower at 6,200 RPM and a massive 490 lb-ft torque at 4,800 RPM. This LS stroker operates across a 2,800 to 6,500 RPM range and demands 93-octane premium gasoline to suppress high-load detonation. Manifold vacuum settles at 12 in-Hg at an 850 RPM idle. Hot operating oil pressure registers between 45 and 65 PSI.

Frame Envelope Transmission Connections

Exterior dimensions mirror standard Gen III LS blocks, fitting between frame rails with matching swap headers. The internally balanced crank tail accepts standard zero-balance flexplates or flywheels for 4L80E or Tremec manual transmissions. Engine mount locations fit standard LS conversion brackets, leaving generous space for tubular exhaust headers and steering linkages.

Lubrication Protocols Application Disclaimers

Pre-pressurize the oil galleries with a pressurized pre-lube canister until lubricant flows across all rocker arms before initial start. Use conventional 10W-30 petroleum break-in oil fortified with high zinc content to protect moving surfaces. This engine is not built for boat marine drives, forced induction boost past 6 PSI, or multi-stage nitrous systems.

• Replace the break-in motor oil and spin on a heavy-duty oil filter after the first 500 vehicle miles.
• Inspect valve spring seat pressures and check header flange bolt torque every 3,000 miles of operation.
• Examine timing cover seals and inspect oil pan perimeter bolts every 12 months or 12,000 miles.

Warranty Statement Physical Manifest

This LS stroker carries a 12-Month factory limited warranty for authorized recreational and street-strip vehicle use. The heavy-duty shipping container holds the assembled long block, aluminum cylinder heads, timing cover, oil pan, valve covers, instruction manual, and certified engine dynamometer sheet.