ATK LM7-LB-4 Chevy LM7/LS1 383CI Base Engine 540HP+



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This is an LM7 (Iron LS1/LS6) based engine with CNC Ported Cathedral Port Aluminum heads making a very streetable 540HP+. Expect big mid to upper end power, will have a noticeable idle. For optimal Performance you will need headers, chassis dyno tune and 36lb injectors. Your engine may not necessarily come with all components listed, but they are listed as our recommendations of parts to run for optimal performance.

Engine Specifications:
• HP: 540
• TQ: 505
• Block: OE LM7 5.3L Gen III
• Bore/Stroke: 3.903” x 4.000”
• Displacement ( 383
• Crankshaft: K1 4340 forged 24 tooth
• Rods: Scat 4340 forged I beam 6.125” with ARP 8740 bolts
• Pistons: Wiseco forged 10.6:1 compression
• Rings: Moly
• Camshaft: Hyd. Roller
• Cam Specs: 228/234 @50 .604/.609 112LSA
• Timing Chain: Billet HD .250” roller
• Cylinder Heads: CNC ported cathedral port cores 2.02/1.60 valves, dual springs, titanium retainers
• Rocker Arms: OE 1.7 ratio
• Oil Pump: Melling

Recommended Components:
• Flexplate/Flywheel: Stock internally balanced
• Balancer: Stock internally balanced/per application
• Intake Manifold: Stock/Aftermarket EFI intake or Carbureted setup
• Water Pump: Per application
• Fuel Pump: Electric per application
• Fuel Injectors: 36lb injectors
• Spark Plugs: NGK #3186
• Spark Plug Wires: Factory

Engine Info:
• Oil: Conventional / Non Synthetic 10W30
• Oil Filter: Wix or K&N
• Timing: Set to factory specifications via PCM module (ECM TUNING REQUIRED).
• Spark Plug Gap: .040”
• Firing Order: 18726543
• Octane: 91+
• Stall Converter: 2500+
• Exhaust: 1 5/8 + Headers

Notes: This engine can replace the 1999-2007 Chevy 5.3L LM7 engine with supporting modifications or any other factory LS equipped vehicle. It can also be retrofitted for aftermarket EFI/Carb setups. ECM MUST BE TUNED, not doing so can damage the engine. : A PCV valve must be ran; please follow the valve cover instructions provided. You must also run an Air-Oil separator system such as the Moroso #85487 to capture the excess crankcase vapors LS engines are known for. If you are not running a MAP Sensor, the MAP timing option in the timing control box must be zeroed out all the way across. Failure to do so will allow the controller to add timing which can lead to detonation. You must also run some sort of a steam line kit that dumps to your water pump, radiator or radiator hose; we recommend a 4 corner setup like the Trick Flow #TFS-306SB601. This allows air pockets/hot spots to escape the heads and can also be used to purge out trapped air when filling the radiator for the first time.


Disclaimer: The parts listed are ATK’s recommendations of parts to be used to obtain our power figures listed. Power figures can vary based on parts used by the end user. It is the customer’s responsibility to verify components will work in their application. Some modifications to the vehicle may be required using these and or other aftermarket parts. . ATK reserves the right to substitute parts used in engines if necessary.



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