S&S Cycle Sidewinder 3 5/8 Big Bore Cylinders for 1936–1999 Big Twins - Manual (Page 17)

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13. Modify knuckleheads for S&S® Oil Return Conversion Kit (knuckleheads installed on 1948 and later cases)
NOTE: Stock knuckleheads return oil down pushrod tubes using breather crankcase vacuum in 1936–'47 cases. If knuckleheads are installed on 1948 and
later cases, an alternative route must be made to return oil from heads. S&S Sidewinder® kits for knucklehead engines for 1948 and later cases
include cylinders equipped with special fittings, hoses and clamps for routing head oil to 1948 and later cylinder return passageways.
Procedure for this modification is as follows:
A. Thoroughly clean valve spring cover cups which fit between guide and head. Be sure oil lines are completely clear as these often become
partially or totally blocked.
B. Mock up engine placing heads on cylinders with valve cover oil return line assemblies in place to observe how stock oil return lines from
cups should be reshaped and bent to provide neat, unobstructed routing towards oil return fittings in Sidewinder cylinders.
C. Carefully bend stock oil return lines and cut them off at appropriate distance so final hookup can be made using hose and clamps provided
in kit. If old oil return lines are not useable, heat and remove from cups and braze in new tubing to provide proper hookup.
NOTE: Steel tubing must be free of sharp bends so oil will return from heads properly. Return hoses must not contact cylinder or head fins.
Restricted flow through oil return lines may cause unwarranted oil buildup in valve covers which may leak past valve guides causing
engine to burn oil.
Oil line must not contact any hot surfaces such as cylinders where it could melt and catch fire.
14. Piston to Valve Clearancing and Piston Installation (All)
NOTES:
• All valve spring spacing, rocker arm to collar, and rocker arm to rocker cover clearancing must be done before piston to valve clearancing can be
checked.
• S&S pistons have sufficient valve clearance when used with most street high performance cams with lifts up to .525”. However, we recommend that
valve clearancing be checked if other than stock cam is used.
Piston to Valve Clearance
Check piston to valve clearance in following manner:
A. Assemble engine with exception of cylinder heads.
B. Turn engine over until piston in front cylinder is at top dead center. Paint area around valve pockets on pistons with machinist’s blue.
C. Place valves in cylinder head leaving off springs and retainers. Place head on cylinder and secure with one bolt.
D. Lower valves until they contact piston. Rotate valve marking painted area.
E. Remove head and check points of contact. Valve should fit in recessed area machined in piston dome.
NOTE: S&S recommends at least .060" clearance around periphery of valve.
F. If insufficient clearance exists, remove piston and grind valve pocket until head of valve fits flush with proper clearance.
G. Repeat procedure for other cylinder head.
H. Spread layer of putty into valve pockets in both pistons.
I. Assemble cylinder heads and bolt assemblies on cylinders with head gaskets in place. Install pushrods and adjust to simulate final
assembly.
J. Turn engine over in normal direction of travel two complete revolutions.
K. Disassemble engine and check thickness of putty in valve pockets.
NOTE: S&S® recommends at least .060" clearance between valve and piston valve pocket recess. While .060" clearance is recommended minimum, it is
advisable to have .080" and up, if possible.
CAUTION
WARNING