GM 5.7L Pre-Vortec Cylinder Head Assembly | Sierra 18-4485HPGM 5. 7L Pre Vortec Cylinder Head Assembly Sierra 18 4485HP Completely assembled new marine cylinder head fits GM 350 cu. in. marine engines with 12 intake manifold mounting bolts. Fits 5. 7L GM V8 PRE Vortec engines from 1987 1995 with press in rocker arm studs and 12 intake manifold mounting bolts (4 inside intake manifold bolts at 23 degrees) Uses center mount valve covers Complete new casting assembly with new stainless steel valves, hardened