ATK SMIHP5.3 GM 5.3L LM7 LS Vortec Long Block Engine, 385 HP

Ready to wake up a tired 5.3L truck or build a stout, budget-friendly LS swap for your hot rod? The ATK High Performance SMIHP5.3 5.3L long block delivers a serious step up over stock, making 385+ horsepower and 390+ lb-ft of torque. It is built as a direct performance upgrade for 1999-2007 Chevy trucks with the LM7 5.3L, and it is equally at home in an LS-swapped street rod, muscle car, or truck.

This remanufactured engine starts with a seasoned OE LM7 iron block, so internal stresses are already relieved for stable, long-lasting bore geometry. Inside, the internally balanced OEM GM 3.622 in. stroke crank with 24-tooth reluctor wheel and OE GM forged powdered metal rods are paired with hypereutectic dish pistons at 9.5:1 compression and moly rings for strength and pump-gas friendly reliability. A custom-ground hydraulic roller camshaft brings big mid-range and upper-RPM power along with a noticeable, aggressive idle. OE aluminum cylinder heads with 61.15cc chambers, 1.89 in. intake and 1.55 in. exhaust valves, and 1.7 ratio rockers finish off the top end. Cam bearings are installed and clocked to the OEM position, and brass freeze plugs and oil galley plugs are installed and sealed. Cam specs are included with the engine.

Engine Specifications:

• Horsepower: 385+
• Torque: 390+ lb-ft
• Displacement: 5.3L (325 ci)
• Bore x Stroke: Up to 3.809 in. x 3.622 in.
• Block: Seasoned OE LM7 5.3L cast iron
• Crankshaft: OEM GM, 3.622 in. stroke, internally balanced, 24-tooth reluctor wheel, .857 in. flange
• Connecting Rods: OE GM forged powdered metal, 6.098 in., stock bolts
• Pistons: Hypereutectic dish, 9.5:1 compression
• Rings: Moly
• Camshaft: Hydraulic roller, custom performance grind (specs included with engine)
• Cam Bearings: Installed and clocked to OEM position
• Cylinder Heads: OE aluminum, 61.15cc chambers, 1.89 in./1.55 in. valves
• Rocker Arms: OE powdered metal, 1.7 ratio
• Freeze Plugs: Brass, installed and sealed
• Oil Galley Plugs: Installed and sealed
• Rear Main Seal: 1-piece
• Balance: Internal
• Weight: 385 lbs.

Not Included: Intake manifold, throttle body, oil pan, valve covers, timing cover, water pump, harmonic balancer, flexplate/flywheel, spark plugs, plug wires, computer, and wiring harness.

Recommended Components:

• Oil: 5W-30
• Fuel System: OE EFI system with upgraded injectors
• Intake: Stock car-style fuel-injected intake (truck intakes will make less power)
• Harmonic Balancer: Stock, internally balanced
• Flexplate/Flywheel: Stock, internally balanced
• Spark Plugs: Stock, gapped at .035 in.
• Ignition Timing: Factory specification via PCM (tune required)
• Firing Order: Stock
• Fuel: 91 octane minimum
• Torque Converter: Stock or 1,800 RPM stall
• Exhaust: 1-5/8 in. or 1-3/4 in. primary tube headers