S&S Cycle Cylinder Heads for Harley-Davidson Twin Cam 88 Engines - Manual (Page 5)

NOTE - Light coating of oil on head bolt threads minimizes
friction so torque values are not distorted. It cannot be
emphasized enough how important it is 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. Excessive torque values may cause
studs to pull out of crankcase.
3. Finish Assembly of Top End, Install Carburetor and Replace
Gas Tanks
NOTE- There are two ways for the front S&S® 79cc head to
breathe, through a vacuum port into the intake port or through
the air cleaner. The position of a set-screw must be moved to
change the breathing format. S&S 79cc front heads are delivered
for vacuum breathing into the intake port, with the set screw
installed in Hole 1.
A. As delivered, the S&S 79cc front head is set up for
vacuum breathing with the set-screw positioned in Hole
1. The rear head can only breathe through the air
cleaner. This is the suggested breathing method for S&S
79cc heads. See Picture 2.
B. If you choose to set the front head to breathe through
the air cleaner, move the set-screw from Hole 1 to Hole
2. See Picture 1 and torque it to 20-36 in-lbs.
Do not run the S&S 79cc head with both Hole 1 and Hole 2
sealed. Also, Do not run the head with both Hole 1 and Hole
2 open.
C. Gaskets for the front and rear heads are identical—but
must be installed so that the “J-shaped” channel is
positioned towards the intake manifold. (See Picture 1).
This may cause one to be installed with the printed side
facing up while the other is installed print side down.
The print on the gasket is not a factor in its function.
D. The gasket included with S&S 79cc heads measures
.039”—which is .019” thicker than other S&S gaskets
that measure .020”.
E. If you are using the stock air cleaner, the through hole
in the two breather screws must be enlarged using a
9/64 (.1406”) diameter drill.
Do not use any other gasket than the supplied (10 pack, PN
90-4125) (2 Pack, PN 90-4120) .039” thick gasket on S&S 79cc
heads.
F. Follow Harley-Davidson ® factory procedures outlined in
Harley-Davidson ® service manual to assemble rocker
cover components and other parts that were removed
for top end service.
G. Assemble rocker arms, pushrods and pushrod tube
assemblies and adjust pushrods.
H. Install intake manifold using provided mounting flanges
and O-ring seals. Be sure O-rings and flanges are
assembled in correct sequence. See Figure 3.
Use flange marked “F” on front head and flange
marked “R” on rear. Slotted end of mounting flange
goes toward lower manifold mounting hole. Flat
washer provided is used on slotted end of flange.
NOTES -
G The intake port diameters of S&S heads are larger than stock
and require the use of an S&S manifold.
G S&S compression releases cannot be used on stock Harley-
Davidson ® heads. They can only be used on S&S cylinder
heads that have been specially designed and machined for
them.
G The intake port diameters of S&S heads are larger than
stock and require the use of an S&S intake manifold and
manifold seals. When used together, the S&S intake
manifold and manifold seals still allow use of stock
manifold mounting flanges.
D. Install carburetor and air cleaner assembly using
appropriate carburetor instructions.
E. Reassemble gas tanks and all other parts that were
dissembled during preparation for top end service. Be
sure there are no gasoline leaks and that throttle opens
and closes smoothly and snaps shut when released.
NOTE - Throttle must not bind and must snap shut to fully closed
position when released.
5
CAUTION
Picture 2
Figure 3
DANGER
Hole 1
Hole 2
WARNING