Proflow Cylinder Heads, LS3 SuperMax 273, Holden Commodore, Chev, Aluminium, Bare (6Bolt) , 70cc Chamber, 273cc, 15deg, Pair - PFEAHCLS3-273-6B-BPart Number: PFEAHCLS3 273 6B B LS3 SuperMax 276 CNC, Aluminium Cylinder Heads 15deg, Holden Chev, Bare 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.