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ATK Engines SP86

ATK Engines High Performance Short Block GM LS 403ci


made in usa
Free Shipping Ships directly from the manufacturer on 12/03/19
Save $10 off $199, $45 off $499, $100 off $999. Promo Code: FALLFUN exclusions apply

ATK Engines High Performance Short Block GM LS 403ci $4,850.99
Out of stock
High Performance Short Block
  • GM LS 403ci Stroker
  • Aluminum LS2 Block
  • 4340 Forged Crankshaft 58 Tooth
  • 4340 Forged H Beam Rods
  • 2618 Forged Dished Pistons -15cc
  • ATK Engines SP86 Details

    LS Gen III/IV

  • 58 Tooth Reluctor

    This short block is built for naturally aspirated engines.

    Block Information:

    • New 2005-2009 GM L92/LS3 Aluminum Block
    • Bore/Stroke: 4.005" x 4.000"
    • Displacement: 403ci
    • Camshaft Bearings: Installed and clocked to OEM position
    • Freeze Plugs: Installed and sealed
    • Oil Galley Plugs: Installed and sealed

    Rotating Assembly:

    • Crankshaft: K1 4340 forged 58 tooth reluctor wheel
    • Rods: K1 4340 Forged H Beam Rods with ARP 2000 bolts
    • Compression Ratio: 64cc= 10.2:1 68cc= 9.8:1 / 72cc= 9.5:1 
    • Pistons: Wiseco 2618 Forged dished -15cc
    • Rings: Plasmamoly

      Recommended Components:

    • Balancer: Internal balance
    • Flexplate/Flywheel: Internal balance
    • Head Gasket: .051" thickness or per application
    • Oil: 10W40 Non synthetic for first 3000 miles
    • Oil Filter: Wix or K&N per application
    • Oil Pump: Melling #689-10296 with high pressure spring


    DOD holes are NOT plugged. If your application does not require DOD/AFM you must plug the oil fill holes. Failure to do so will cause an internal oil leak causing low oil pressure problems.

  • Specifications:

    Sold individually
    Manufacturer's Part Number:
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    In 2007, ATK launched a High Performance Division with one of the finest engine shops in the country. By reverse engineering all of their engines, they are able to eliminate any OEM deficiencies. This makes an ATK built crate engine have a superior design over the original engine by incorporating better components when needed. ATK short blocks will start any build with a solid foundation. GM short blocks are generally packaged as the engine block assembled with pistons, piston rings, and crankshaft installed.

    JEGS Easy Kits are designed by JEGS high performance racing professionals to help you get all the performance parts you need for your race car, hot rod or truck.

    Some parts are not legal for use in California or other states with similar laws / regulations

    Motor Vehicles

    WARNING: Motor vehicles contain fuel, oils and fluids, battery posts, terminals and related accessories which contain lead and lead compounds and other chemicals known to the State of California to cause cancer, birth defects and other reproductive harm. These chemicals are found in vehicles, vehicle parts and accessories, both new and as replacements. When being serviced, these vehicles generate used oil, waste fluids, grease, fumes and particulates, all known to the State of California to cause cancer, birth defects, and reproductive harm.


    WARNING: Some dust created by power sanding, sawing, grinding, drilling, and other construction activities contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Some examples of these chemicals are: lead from lead-based paints, crystalline silica from bricks and cement and other masonry products, and arsenic and chromium from chemically treated lumber. Your risk from exposure to these chemicals varies, depending on how often you do this type of work. To reduce your exposure, work in a well-ventilated area and with approved safety equipment, such as dust masks that are specially designed to filter out microscopic particles.

    Electrical Cords

    WARNING: The wires of these products contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling.