S&S Cycle Big Twin Engines with 3-1/2 and 3-5/8 Bore Crankcases and Special Application (SA) 4 Bore Crankcases User Manual

Page 9

Engines ordered for ‘84-’92 year group will require the
following additional parts for dual venting: S&S

air cleaner

backplate #17-0336 and hardware packet #17-0439. Both are
available from S&S.

NOTE - 1992 was a transitional year for some Harley-Davidson

models. While cylinder head venting was introduced in 1992,
many motorcycles sold as 1992 models retained crankcase
venting. Gear cover, gear cover gasket, lower rocker covers, and
lower rocker cover gaskets must be identified by year group to
determine possible vent arrangements.

NOTE - Using ‘93-up gear cover or gasket on S&S big twin engines
set up to vent out crankcase will result in large oil losses out
crankcase vent opening.

NOTE - Using ‘91-older lower rocker covers or gaskets in engines
set up for cylinder head venting will obstruct cylinder head vent
passages, causing oil leakage and possible damage to other
components. See Picture 22.

NOTE - If ‘93-up lower rocker covers are used in engine set up for
crankcase venting only, oil seepage past cylinder head vent
passage inserts may occur. It is recommended that ‘91-older lower
rocker covers be used in engine set up for crankcase venting only.

Install vent hardware (big twin):

1. For crankcase and dual venting, install 45˚ elbow, #31-2022,

in crankcase vent opening per S&S Crankcase Instructions
#31-0000M. If engine to vent out cylinder heads only, plug
crankcase vent opening with socket head pipe plug
#31-2023. Steel fittings such as elbow and plug must be
coated with anti-seize thread sealant such as Slic-Tite

or Teflon

tape before installation in crankcase or

cylinder head.

2. For crankcase venting only, install threaded inserts #90-4026

in cylinder head air cleaner mounting bolt holes. See
Carburetor Instruction Sheet #51-1012.

Note- Shovelhead engines vent out crankcase only.

INSTALL PISTONS AND CYLINDERS
(All Unassembled)

1. Identify front and rear pistons according to “Piston

Installation” section in S&S Pistons Instruction Sheet
#51-1028. Piston Series number will appear on box
containing piston assembly.

2. Inspect pistons, especially areas around machined surfaces

such as ring grooves and wristpin holes, for burrs. De-burr as
necessary, taking care to remove particles that could become
dislodged inside engine.

3. On big twin engines that will be operated in extremely hot

climates such as American South, Southwest, or areas with
only low octane gasoline available, carefully round sharp
edges on piston dome and in combustion chamber. A die
grinder and small, flexible sanding wheel work well for this.
See Picture 22.

4. Measure ring end gaps and adjust as necessary. See S&S

Piston Instruction Sheet #51-1028, “Ring Installation” for gap
specification applications.

5. Thoroughly clean cylinders, pistons, rings, wristpins, and

wristpin retainers in solvent, then hot, soapy water. Take
special care to flush oil passages, and pass clean, white cloth
back and forth through wristpin bores. Dry all with
compressed air and place on clean, dry surface.

6. S&S recommends installing all cylinder base gaskets dry.

Builders who prefer sealant may use sealant of choice on
shovelheads, but big twin gaskets are different material and
must be installed dry. Be sure holes in gaskets align with
cylinder base dowels and oil holes.

7. Install rings on pistons as described in Piston Instruction

Sheet. S&S recommends covering cylinder studs with 3/8” I.D.
fuel line to protect rings until cylinder installed.

Lubricate connecting rod wristpin bushings with light coat of
assembly lube. Install rear piston, wristpin and retainer on
connecting rod per piston instructions.

9. If big twin cylinders, install cylinder head alignment dowels

in cylinder.

NOTE - Tight clearances resulting from reinforced S&S cylinder
design require that S&S shovelhead base nuts and two head bolts
(ones nearest exhaust pipes on cam side of engine) be inserted
and held in place as cylinder lowered over studs. See Instructions
for S&S Sidewinder

Big Bore Cylinders No. 1000, page 12.

Picture 21

Picture 22

1992-Earlier

1993-Later

Round areas shown in both valve reliefs.