ATK Core Return Process
JEGS and ATK appreciate your business and want to ensure that your core return is as smooth as possible.

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NOTE:

• Core return can be any Big Block Chevy 454ci engine

Engine Specifications

• Horsepower: 565 hp
• Torque: 595 lb/ft

Block Information:

• Seasoned OE 1991-1995 Gen V 4 bolt main 1pc seal (no mechanical fuel pump provision)
• Bore/Stroke: 4.310" x 4.250"
• Displacement: 489ci

Rotating Assembly:

• Crankshaft: Scat nodular iron
• Balance: Internal 
• Rods: Scat 4340 forged I beam 6.385" with ARP 8740 Bolts
• Compression Ratio: 10.1:1
• Pistons: Forged
• Rings: Moly

Camshaft Specs:

• Camshaft: Hydraulic roller
• Cam Duration @ .050": Intake 237 / Exhaust 243
• Cam Lift: Intake .635" / Exhaust .640"
• Lobe Separation Angle: 112lsa
• Timing Chain: Double roller

Cylinder Head Information:

• Cylinder Heads: Edelbrock E-Street aluminum
• Combustion Chamber: 110cc
• Intake Runner: 290cc
• Valve Size: 2.19" Intake / 1.88" Exhaust
• Rocker Arms: Billet aluminum roller rockers 1.7 ratio

Oil Pan Information:

• Oil Pan: OE 5qt 
• Oil Pump: Melling high volume

 Base Engines

• Short Block
• Camshaft
• Timing Set
• Cylinder Heads
• Valve Covers
• Timing Cover
• Oil Pan
• Oil Pump & Pickup Tube
• Flexplate

Mid Dress Engines

• Consists of Base Engine Build
• Intake Manifold
• Distributor
• Water Pump 
• Harmonic Balancer

Complete Engines

• Consists of Mid Dress Engine Build
• Fuel Pump
• Carburetor 
• Spark Plug Wires
• Spark Plugs

Recommended Components

• Exhaust: 2" Headers
• Firing Order: 18436572
• Octane: 91+
• Oil: 10W30 (Conventional / Non Synthetic) 
• Oil Filter: Wix or K&N
• Spark Plug Gap: .035"
• Stall Converter: 2800+
• Timing: 34-36 Degrees 

• Balancer: Internal balance 8"
• Carburetor: Quick Fuel 780cfm vacuum secondary electric choke #793-HR-780-VS
• Distributor: HEI (iron gear)
• Flexplate: Internal balance 
• Fuel Pump: No mechanical fuel pump provision, must run an electric pump
• Intake Manifold: Edelbrock Performer RPM dual plane #350-7161
• Spark Plugs: Autotile #417-3923
• Spark Plug Wires: 8mm
• Water Pump: OE long pump

 Disclaimer: The parts listed are ATK's recommendations of parts to be used to obtain the power figures listed. Power figures can vary based on parts used by the end user. Some modifications to the vehicle may be required using these and or other aftermarket parts.

Engine Break-In Procedure

Use or break-in oil or conventional (non-synthetic) 10w30 oil with zinc additive for the first 500 miles of operation.  Do not drive for long periods at any single speed, always vary your speed. Do not tow a trailer or put other heavy loads on the vehicle. It is best to avoid long periods of idling during this period. Check the engine oil and coolant levels daily. 

Engines with flat tappet hydraulic cams only - Run the engine between 2,000 and 2,500 RPM's, with no-load on the engine for the first 30 minutes. Let the engine cool down completely and repeat process 2-3 more times. Do not idle the engine for any extended period at this time, this is critical to break in the camshaft.

At 500 Miles change the engine oil and filter using conventional (non-synthetic) oil with a zinc additive. Check fuel and ignition settings, adjust valves (where applicable).  Drive the next 500 miles normally, without high RPM's (below 5000 RPM), hard use, or extended periods of high loading or long periods of idling.

Change the oil and oil filter again at 1,000 miles. Continue using conventional (non-synthetic) oils and zinc additive, until about 4,000 miles. At that point, you may run a quality 10w30 synthetic oil if you choose. 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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