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

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NOTE: Boring cylinder spigot holes in cases to accommodate big bore cylinders will machine a notch on center case bolt and bolt immediately to rear of
rear cylinder. These bolts must later be placed in same position as when machined to prevent unwarranted stress on cylinder base spigots.
Unwarranted stress on cylinder base spigots may cause possible damage to cylinders, pistons and/or other engine components.
NOTE: To make repositioning these studs easier later, we recommend sawing slots in ends so that they may be turned with a screwdriver after installation
in cases.
Perform following procedure to bore crankcases:
A. Hacksaw screwdriver slot .050" deep in top center case bolt and bolt immediately to rear of rear cylinder.
B. Clean cases thoroughly and assemble using all case bolts.
C. Position slots in center and rear studs so slots are perpendicular to or parallel with base gasket surface or lined up with some easily
identifiable point on case and tighten all case bolts as in final assembly.
D. Place masking tape over both ends of camshaft and mainshaft bearings to keep out chips.
E. Bolt boring plate to bench or stand leaving squared end of plate protrude over edge approximately 7 .
F. Procure four nuts from local hardware store, 7⁄16-20 thread for early cases and 3⁄8-16 thread for 1984–’99 models, and bolt cases to plate
using all four studs. Big twin 1984–’99 cases with late style male studs must be spaced away from plate by using boring spacers, Parts #53-
0007 and #53-0008. Be careful not to damage studs.
Damaged studs may cause stress risers which can lead to stud failure and possible damage to engine components.
G. Center boring bar head in cylinder spigot bore in crankcases, not hole in plate.
NOTE: Some bar centering tools are pointed which may dig into soft crankcase aluminum. Be careful when centering bar. For greater accuracy center
once, then rotate bar 90˚ and retap-center.
H. Shovelhead and Harley-Davidson® Evolution® cases - bore hole to diameter of 3.878" to 3.880" by 15⁄8" deep. Measure depth perpendicular
from cylinder base gasket surface. Knucklehead and panhead cases - bore hole to diameter of 3.878" to 3.880"by 11⁄8" deep.
NOTES:
• We normally take three cuts to bore cases, 3.800" diameter, 3.850" and final size 3.879". If you machine into boring plate on final cut, this is
of no consequence since hole in plate is never used as machining reference point.
• Boring to a shallower depth leaves more material in older, weaker crankcases. This also minimizes possibility of breaking into oil supply
passages to heads on panhead cases. If cutter breaks into passage, thin wall brass modeling tubing (available at many hobby shops) may be
used to repair damage. To repair damage using this method, perform following steps:
1. Grind 45˚ angle on end of tubing to be inserted in case and remove burrs.
2. Press angled end of tubing into passageway at base gasket surface until tubing bottoms in passageway and seals damaged area.
3. Locate hole that supplies damaged passage and blow air into it to be sure passage is clear. Rotate tubing to point where air pressure
escaping is greatest.
4. When air passes freely, carefully cut off tubing flush at base gasket surface and debur.
5. Peen tubing down that is exposed in damaged area so that it does not protrude above machined surface of crankcase spigot hole. |
Do not overpeen tubing to where passage is sealed off.
A restriction in oil feed passageway to cylinder heads may cause a loss of oil pressure to heads resulting possible damage to rocker
arms and/or other engine components.
I. Repeat steps F to H for other spigot bore.
CAUTION
CAUTION
CAUTION