Mast Motorsports Rectangular Port LS3 11 Degree 6-Bolt Med Bore CNC Assembled (4.000″-4.070″ Bore)

• Designed for any new Gen IV short-block with 4.000″ bore or larger
• The 6-Bolt design is compatible with GM LSX and World LSX blocks
• Accepts Gen IV LS3 valvetrain and intake manifolds.
• Uses a 2.165″ intake valve and 1.600″ exhaust valve
• Has a 256cc intake port
• Has a 69cc combustion chamber standard
• Has a deck thickness of .750″

Each Mast Black Label cylinder head assembly includes:

• A fully CNC machined Mast Black Label aluminum cylinder head
• Mast micro finished .650 lift beehive valve springs
• Mast lightweight stainless steel intake & exhaust valves
• Mast lightweight steel retainers
• Mast machined locks

NOTE: Gaskets, valve covers, rocker arms and pushrods not included

Flow Data w/4.070″ Bore Plate

Lift Intake Exhaust

0.100 77 56

0.200 148 118

0.300 237 165

0.400 295 208

0.500 328 227

0.600 351 235

0.700 370 241