S&S Cycle Sidewinder 3 5/8 Big Bore Cylinders for 1936–1999 Big Twins User Manual
Page 21
21
NOTES
• Most 1984–'99 model Sidewinder® engines are designed with .055" piston to head clearance, squish, which is provided by thickness of head gasket.
Therefore, in most cases pistons at top center should be flush with head gasket surface of cylinders. If pistons are higher than cylinders at top dead
center, then something is wrong and S&S® should be notified.
• If additional compression is desired for racing purposes, a minimum of .040" squish can be run. Fifteen thousandths, .015", less clearance removes
about 2.5ccs from stock combustion chamber volume. This adds about .25 to compression ratio. It is not recommended to run this amount of
clearance unless engine is checked periodically since contact with head due to carbon buildup and wear may result after a period of time.
Insufficient clearance between piston domes and cylinder heads will damage pistons, heads and/or other engine components.
D. Coat piston skirts with engine oil and install cylinders.
E. Install head gaskets dry. If included, place o-ring seals on line up dowel oil return tubes and be sure head gaskets are properly positioned.
F. Before installing heads spin each headbolt down on it’s respective stud to be sure threads are clean and free of contamination. Place a
drop or two of oil on threads of each head bolt just prior to final assembly.
NOTE: Light coating of oil on head bolt threads minimizes friction so torque values will not be distorted. It cannot be emphasized enough to do these
steps carefully. Maintaining a good head gasket seal depends on it.
Improper torquing sequence and head bolt torque values may cause head gasket failure.
G. Bolt heads on cylinders. Tighten bolts in stages using crossing pattern. See Figure 7. If using stock crankcases, follow the same bolt
tightening sequence, but use stock three stage procedure and torque values shown. If using other aftermarket crankcases, contact the
manufacturer for recommended head bolt torque specifications.
IMPORTANT NOTE: Proper first time engine start-up and break-in for first 15 minutes is critical to achieve permanent and lasting head gasket seal.
Follow “Engine Break-In” procedures at end of section 16.
Improper first time engine start-up and break-in procedure may cause head gasket failure.
H. Finish assembling top end per factory procedure. Install pushrods and adjust using instructions provided.
CAUTION
CAUTION
CAUTION
Figure 7
Torque sequence for 1984–'99 big twin top view
Driveside
Camside
1
2
3
4
2
1
4
3
S&S® Crankcases
Stock Crankcases
Stage 1
8 ft-lbs.
7-9 ft-lbs.
Stage 2
18 ft-lbs.
12-14 ft-lbs.
Stage 3
Turn additional 90˚ or 1⁄4 turn
Turn additional 90˚