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Rocker Box Kit 1984–'99 Big Twin & 1986–2003 XL

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Product Reviews

S&S manufactures two types of rocker covers for Harley-Davidson® Evolution® big twin engines: billet and die-cast. Billet covers are CNC machined from aluminum billets. Cast covers are made using the more economical die casting process. All S&S rocker covers include formed Viton® o-rings for leakfree operation; our proven two-piece design makes for a simple installation. Which is better—billet or die-cast? Both work equally well for most applications. The billet covers will allow the use of larger diameter valve springs and valves with extra long stems without additional clearancing. However, in the vast majority of street applications, whether using S&S or stock cylinder heads, either style rocker covers can be used according to the builder's preference and budget.

Features and Benefits:

  • OEM-style "umbrella" fittings are included with billet rocker boxes for 1993–'99 big twin engines with cylinder head venting.
  • Cast rocker boxes use an exclusive one way valve, which is built into the rocker cover gasket to control oil carry over in "head breathing" engines.
  • S&S billet rocker covers are available in two finishes: show-quality chrome, or unfinished. Unfinished is ideal for powdercoating and other custom cosmetic treatments. Die-cast covers are available in chrome finish only.
  • Installation on stock and most comparable sized engines can be performed without removing the engine from the frame.

Choose Die-Cast (Chrome) or Billet (in Chrome or Unfinished)

Billet Chrome. . . . .90-4050
Billet Unfinished. . . . .90-4055
Die-Cast Chrome. . . . .90-4095

NOTE:In spite of the similarities between different S&S billet and cast rocker covers, not all parts are interchangeable.

The performance-oriented design of the billet rocker boxes permits valve lifts up to .710" with stock or S&S Super Stock® heads, and up to .810" with S&S Special Application heads. S&S roller rocker arms are recommended for high lift cams. Cast rocker boxes may require some minor clearancing, and it is recommended that they be ordered either polished or unfinished, so that clearancing may be done without disturbing chrome plated surfaces.

S&S billet rocker covers accept valve springs up to 1.660" O.D. without modification. Cast rocker boxes may require minor clearancing. Cylinder heads must be set up correctly for high-lift cams, and it remains the builder's responsibility to confirm all clearances.

Kits include front and rear cover assemblies with base and top cover, rocker shaft supports, gaskets and o-rings, and instructions.

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