Proflow Cylinder Heads, LS3 SuperMax 276 CNC, Bare, Holden, Chev Aluminium, (6-Bolt ) LS3/L76/L77/L92/L98/LSX, 276cc Intake, 70cc Chamber, Pair - PFEAHCLS3-276-6BT-PPart Number: PFEAHCLS3 276 6BT P Proflow does not sacrifice quality for a low price you get both with our aluminium cylinder heads. Our LS3 cylinder heads are designed for street race performance engines to give the ultimate in flow at a competitive price. Cast from A356 aluminium, these 15 LS3 rectangle port heads are designed to fit LS series engines with a 4. 00" or larger bore. These bare 275cc heads accept 2. 165" diameter intake valves and 1.