GM LS3 821 Casting Cylinder head complete (Pair)

Upgrade or Replace your cylinder heads with these brand new Genuine GM LS3 821 casting heads! they make the ultimate addition to any LS build.

PLEASE NOTE:  This item is a Special Order Product  and is not held in regular stock. Orders are placed with our supplier once payment is recieved. Estimated lead times may vary depending on supplier availabillity and location. We will confirm an estimated timeframe after your order is placed.

LS3 Cylinder Head Assembly
• Aluminum performance head
• Fits any LS family engine with 4.000" bore or larger
• 2.165" hollow stem intake, and 1.590" solid stem exhaust valves
• .550" max valve lift
• As-cast L92 style intake ports
• D-shaped exhaust ports
• As-cast combustion chambers

Head 12629063 assembled with the following:
• 12569427 Intake Valves
• 10166344 Valve Spring Retainers
• 12582719 Exhaust Valves
• 12482063 Intake Valve Stem Seals
• 12625033 Valve Springs
• 12482062 Exhaust Valve Stem Seals
• 10166345 Valve Locks

Aluminum LS Family Head Technical Notes:
• Manufactured from 319-T5 aluminum alloy
• High-efficiency combustion chambers
• Symmetrical intake and exhaust ports
• Angled spark plugs (14mm; 5/8" hex; 3/4" reach; taper-seat plugs)
• 15° valve angle (except C5R and LS7)
• Bolt-down-type rocker arms (except LSX-DR, LSX-CT)
• Center-bolt valve cover hold-downs
• Fits Gen III and Gen IV Small-Blocks only