Mast Motorsports Rectangular Port LS3 12 Degree 4.125″-4.200″ 6-Bolt Large Bore CNC – Bare Heads

• Utilizes the Gen IV LS7 OEM rockers, but accepts the LS3/L76 intake manifold
• Designed for any new Gen IV short-block with 4.125″ bore or larger
• The 6-bolt design is compatible with GM LSX and RHS Blocks
• Uses a 2.200″ intake valve and 1.600″ exhaust valve
• Has a 270cc intake port
• Has a deck thickness of .750″

Flow Data w/4.125″ Bore Plate

Lift Intake Exhaust

0.100 78 65

0.200 162 118

0.300 243 171

0.400 304 212

0.500 347 229

0.550 362

0.600 376 245

0.650 384 247

0.700 390 249