Sierra Marine Parts Catalog

649 CYLINDER HEAD ASSEMBLIES All cylinder heads are new castings and complete assemblies with new stainless steel valves, hardened steel exhaust seats, valve springs, valve locks and retainers. All GM cylinder heads utilize high performance screw-in rocker arm studs in place of factory press in rocker arm studs. 18-4485 CYLINDER HEAD ASSEMBLY Replaces: MerCruiser 938-883490R1, 938-883490, 938-883490R50, 938-884741R, 938-884741R50 Fits: 5.7L V-8 GM (1987-95) with press in rocker arm studs with 12 intake manifold mounting bolts- (4 inside intake manifold bolts at 23 degrees), center mount valve covers 18-4486 CYLINDER HEAD ASSEMBLY Replaces: MerCruiser 938-883297 1,938-803860T, 938-883297R1 Fits: 5.7L V-8 GM Vortec (1996-Up) with press in rocker arm studs with 8 intake manifold mounting bolts, composite valve cover 18-4489 CYLINDER HEAD ASSEMBLY Replaces: MerCruiser 936-810840/986767, 938-884739R01 Fits: 2.5L/3.0L GM (1968-95) (non MerCruiser LX models) (1968-95) INTERNAL ENGINE COMPONENTS — Cylinder Heads 18-4485HP CYLINDER HEAD ASSEMBLY Fits: Mid GM small block 5.7L high performance. Completely assembled with revised runner and combustion chambers. Add 30hp to stock motor with no additional modifications. 18-4486HP CYLINDER HEAD ASSEMBLY Fits: Vortec GM small block 5.7L high performance Completely assembled with revised runner and combustion chambers. Add 30hp to stock motor with no additional modifications. 18-4484HP CYLINDER HEAD ASSEMBLY Fits: Early GM small block 5.7L high-performance Completely assembled with revised runner and combustion chambers. Add 30hp to stock motor with no additional modifications. 18-4491 CYLINDER HEAD ASSEMBLY Replaces: MerCruiser 938-827178 Replaces 4.3L Vortec V-6 (1996-Up) with screw in rocker arm studs (non-adjustable valve train), 8 intake manifold mounting bolts, center mount valve cover. NOTE: not for use with engines using factory roller rocker arms. 18-4493HP CYLINDER HEAD Fits: Big-block GM cast iron performance