LS3 Style 11 Degree Chevrolet heads designed to fit Gen III LS1/2/6 3.90" bore engines. 248cc intake runners, 69cc combustion chambers. For hydraulic roller cams up to .625" lift. Assembled with Comp Cams 2.08"/1.60" valves, PAC beehive springs, and related hardware. Raised valve cover rails, 6-bolt per cylinder design (Fits LSX blocks too). Includes rocker arm rails for use with LS3 offset (OE style) rocker arms. SEE SPECIAL TECHNICAL NOTES REGARDING ROCKER ARMS. Manufactured from A356-T6 aluminum. Each pair comes with a detailed flow sheet. Pair. Download Data here - DOWNLOAD

• Rocker pedestal mount spacing is 2.115".
  Not for use with rocker systems that use guide plates or have pedestals with OE LS3 spacing.
  
  Head Gasket Cometic #C5475/5751-051 or equivalent
  Head Bolt Torque Refer to OE spec
  Head Bolts ARP #134-3610
  Head Studs ARP #234-4317
  Rocker Arms OE LS3 style ONLY (no stud/guideplate conversions etc.)
  Intake Port (cc) 248cc
  Intake Port Dimensions 2.60" x 1.25"
  Exhaust Port (cc) 102cc
  Exhaust Port Location Stock
  Exhaust Port Dimensions 1.70" x 1.79"
  Exhaust Gasket Remflex #2008 or equivalent
  Intake Valve Size 2.08"
  Exhaust Valve Size 1.60"
  Valve Angle 11°
  Valve Spring Pocket O.D. 1.55"
  Valve Guide Size 8mm .500" (Top) .560" (Base)
  Deck Thickness .750"
  Combustion Chamber (cc) 69cc
  Spark Plug Size 14mm x .750" Gasket (eg. Autolite #3923)
  Spark Plug Location/Angle OE/Angle

Intake Valves: PW 360043
Exhaust Valves: PW 360048
Springs/Retainers/Locks/Locators: PAC PAC-KS13
Viton Valve Seals: PW 360488