Upgrade your 1998 through 2010 Gen 3 or 4 engine with this new 625 HP 427 cubic inch powerhouse specifically designed to replace an existing LS engine. Assembled with a new block and Blueprint heads, forged crank, rods, and pistons. The engine includes a performance hydraulic roller cam and lifters and upgraded roller rockers. Built with a Gen 4 style 58x reluctor and sensors, this engine is a drop in for Gen 4 applications, and by using Blueprint's conversion kit (sold separately), you can also install into earlier Gen 3 applications. 91 octane or better recommended. Engine includes intake manifold, timing cover, valley cover, and rear cover. Injectors, rails, throttle body, coil packs, valve covers, water pump, and oil pan NOT included. In many cases, original parts can be used.

Recommended Stall Converter: 2200+ RPM
Recommended Fuel: 91 Octane

• New block with 1-piece rear main seal
• New Blueprint Cylinder Heads p/n 138-PS8015 with roller rocker arms
• Recommended Spark Plugs: ACDelco 41-985
• GM L92 Intake

Rotating Assembly

• Forged Crankshaft: 4.125" Stroke
• Forged Connecting Rods: 6.125"
• Mahle Forged Pistons
• 11:1 Compression
• Internally Balanced Camshaft Specs
• Hydraulic Roller
• Duration at .050' Lift: 239 Intake, 255 Exhaust
• Lift: .624' Intake, .624' Exhaust
• Lobe Separation: 114°

  Engine Break-In Procedure

  Use or break-in oil or conventional (non-synthetic) multi-viscosity oil with zinc additive for the first 500 miles of operation. Avoid hard acceleration for sustained periods. Periodically change the engine speed while driving to help seat the rings. While the engine is running, be sure to check oil pressure and coolant temperature, and check for fluid leaks, such as oil, transmission fluid, fuel, and coolant/antifreeze. Also listen for any unusual sounds. Should you hear an unusual sound, shut the engine off, check for the source, and correct it.

  Engines with flat tappet cams only - Start the engine and bring it to 2,000 RPM. Get the engine running smoothly. Then vary the engine speed from 1,800-2,200 RPM in a slow acceleration/deceleration cycle for 30 minutes. This is necessary to provide adequate oil splash and lifter rotation to properly mate each lifter to its lobe. 

  At 500 Miles change the engine oil and filter using conventional (non-synthetic) oil. After 6,000 miles, synthetic oils can be used in your engine.  For flat tappet cam engines, continued use of oil with zinc or a zinc additive for the life of your engine is recommended. 

Emissions Note:

This part is only legal for sale and use on Uncontrolled (Non-Emissions Controlled) Vehicles or on vehicles used solely for the purposes of closed competition racing.

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