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Harley-Davidson Performance Guide

Cylinder Heads valves and springs

Performance and Technical information on cylinder heads, valves, valve sizes, valve springs, port size, port shapes and compression ratios for Harley-Davidson motorcycles.

Valve Sizes

For most 80 CID engine applications, use of the stock intake (1.840") and exhaust (1.615") is recommended. Well designed engines with stock valves are capable of producing 100HP and 100 Ft.Lbs. of torque. The expected power band on an engine with stock valve sizes and 100 HP is from 4500 RPM to 6000 RPM.

Valve Spring Pressures and Installation Height

The valve springs installed should be the minimum seat pressure needed to maintain good valve contact. High seat pressures lead to rapid wear of the valve seat area.

Determining installed spring height

  1. Using both top and bottom collars, place the spring assembly in a small vise. Close the vise until the outer spring is solid.
  2. Measure the compressed spring height, without the collars. This measurement will be the solid height.
  3. Calculate the installed spring height using the following formula:
    Installed height = maximum valve lift + .060" + solid spring height
  4. Maximum valve lift numbers can be take from the vendors specifications. As an example, an S&S 561 has a lift of .560". The solid height for a set of Andrews valve springs is 1.190". The installed spring height will be:
    1.810" = .560" + .060" + 1.190"
  5. When you install the springs, check for .050" clearance between the valve guide and the upper spring collar at maximum valve lift.