S&S Cycle Cams for Panhead, Shovelhead, & Harley-Davidson Evolution Engines - Manual (Page 4)

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GENERAL INFORMATION
1. Lifters
A. Camshafts with lifts greater than stock generally have lobes that are taller than stock which means that the cam followers or lifters will travel
a greater distance. For this reason it is necessary to check clearance between the lifter roller and tappet block, and between the rear cam
bearing and pinion bearing race.
B. High performance Harley-Davidson® Evolution® engines equipped with hydraulic lifters can often benefit from using an S&S® HL
2
T Hydraulic
Lifter Limited Travel Kit. In many instances, the HL
2
T kit will help lower cranking compression for easier starting. Additionally, these simple,
low cost kits reduce the likelihood of lifter collapse at high rpm. Kit part number for 1984-1985 Evolution® models with stock lifters and all
engines with S&S 33-5342 lifters introduced in late 1998 is 33-5338. Kit 33-5339 fits 1986-up Evolution® lifters and older S&S lifters 33-5340
and 33-5341.
2. Pushrods
A. Most high performance camshaft installations require the installation of a solid lifter conversion kit or adjustable pushrods. Adjustable
pushrods give the flexibility required to compensate for any differences in cam base circle dimensions, gasket thickness, and cylinder head
modifications. If pushrods are changed, depending upon their design, it may be necessary to do some additional pushrod-to-pushrod
tube and pushrod-to-cylinder head clearancing. This clearancing is necessary because the pushrod angle from the lifter to the rocker arm
changes due to additional lift of the camshaft. All S&S pushrods with tubing diameters of 7⁄16" or less can be used with any S&S cam without
additional clearancing. It is recommended that these clearances be checked if another pushrod type is used. Consult the pushrod installation
instructions. S&S makes adjustable chrome-moly steel pushrod kits for all big twin applications.
3. Rocker Arms
A. Additional camshaft lift causes additional rocker arm travel. Older engines should be checked to see if the rocker arm ends that contact the
valve are irregular or worn excessively. If they appear serviceable, they should then be checked to see how they contact the end of the valve
during a complete opening and closing cycle. The extra travel of the valve caused by a high lift cam may cause the rocker arm to contact the
valve improperly at the full open position. If irregular contact due to excessive wear is present, the rocker arm should be replaced.
B. Additional rocker arm travel may reduce the existing clearance between the rocker arm and rocker cover and between the rocker arms and
the top valve spring collar. This is of particular concern in instances where the valves have receded deep in the head due to worn valve seats.
Both clearances must be checked and corrected before final assembly. Machinist’s blue or putty can be used to check for contact.
NOTE: S&S recommends the use of roller rockers in high-lift applications to reduce valve stem and guide wear caused by elevated side-loads. Some degree
of side loading occurs with all lifts. The greater the lift, the greater the amount of side-load.
4. Valve Springs
A. Valve springs and top spring collars travel farther with a high lift cam. They must be spaced to prevent the spring from coil binding and
to prevent the top collar from contacting the valve guides. With valve fully open there must be a minimum of .060" additional valve travel
available before any coils of the inner or outer valve springs contact each other. A minimum clearance of .060" must be maintained between
the top valve spring retainer and the valve guide or valve seal when the valve is completely open.
B. The machining process required to prevent coil bind and maintain adequate seat pressures with stock springs can be difficult and expensive.
S&S recommends our .630" lift high performance spring kit 93-2077 (steel collars) or 93-2078 (titanium top collars) for most Evolution®
engines. Kits for higher lifts are also available. S&S offers several high-lift spring kits for shovelheads and panheads. The .550" lift kit 90-2053
(aluminum collars) fits 1948-early 1984 panheads and shovelheads. The .590" lift kit 90-2060 (steel collars) fits 1948-early 1981 panheads and
shovelheads. The 90-2063 kit fits late 1981-1984 shovelheads.
NOTE: S&S also offers panhead and shovelhead kits with titanium top collars. Shortening of the valve guide may be required. Otherwise, these kits virtually
eliminate the need for machining.
C. Because of its .560" lift, an experienced engine builder should install our 560S cam for shovelheads. The installation can be simplified by
using one of the .590" lift valve spring kits mentioned in the preceding paragraph. Moderate TDC lifts mean that, in most existing high-
performance applications, no additional valve-to-piston or valve-to-valve clearancing will be required. Shortening of the valve guide for
adequate top collar-to-guide clearance may be required.
5. Valves and Pistons
A. A high performance camshaft increases the breathing capabilities of the engine by increasing the valve lift and/or duration. Valves that
open higher for longer periods of time run a greater risk of contacting each other or the pistons. If larger than stock diameter valves are used,
valve clearance problems are even more apt to occur.
B. S&S® recommends a minimum of .040" clearance between the valves throughout their opening and closing cycles. This can be checked with
a .040" diameter wire inserted through the spark plug hole.
C. Absolute minimum valve clearance between valves and pistons is .060" for the intakes and .080" for exhausts.
NOTE: Due to the increased lift and duration installation of most high performance camshafts require that valve train clearances be checked and corrected
if needed. Consult cam specifications on first page to determine which checks must be performed.