Sierra Marine Parts Catalog: INTERNAL ENGINE COMPONENTS
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18-4508
HEAD BOLT KIT
High performance head bolt kit-small block GM
18-4504
CYLINDER HEAD
• Aluminum cylinder heads sold in pairs only or 454 & 502 cu.
In big-block GM applications.
• Custom engraved with Sierra High-Performance logo
• 320 cc intake runner/119cc exhaust runner
• 2.25 intake/1.88 exhaust stainless steel valves
• 5 angle valve seat cut
• Up to 65HP increase over OE cylinder heads
• Suitable for use on Mark IV, Gen V, & Gen VI GM blocks.
Must use correct corresponding head gaskets
• Std. BBC 7/16” rocker studs and 3/8” diameter pushrod guideplates
• Rectangle intake ports
• Use on factory non-adjustable valvetrain applications require adjustable rocker arm assemblies such as Sierra’s 18-4507
• Use Sierra 18-4506 guide plates to utilize factory 5/16” pushrods
18-4506
GUIDE PLATES
Big-Block GM with 5/16" pushrods
18-4507
ROCKER ARM KIT (4 VALVES)
Big-Block GM
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.
CYLINDER HEAD ASSEMBLY
Fits: 5.7L V-8 GM (1969-86) with 12 intake
manifold mounting bolts, perimeter mount valve cover
CYLINDER HEAD ASSEMBLY
Replaces: MerCruiser 938-883490 1
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
CYLINDER HEAD ASSEMBLY
Replaces: MerCruiser 938-883297 1,938-803860T
Fits: 5.7L V-8 GM Vortec (1996-Up) with press in rocker arm studs with 8 intake
manifold mounting bolts, composite valve cover
CYLINDER HEAD ASSEMBLY
Replaces: MerCruiser 936-5544, 936-810840/986767
Fits: 2.5L/3.0L GM (1968-95) (non MerCruiser LX models) (1968-95)
INTERNALENGINECOMPONENTS—CylinderHeads
ROCKER ARM ASSEMBLY
Replaces: Mercruiser 35329
Fits: MCM/MIE Gm V6 & V8(283, 305 & 350 cid) engines