S&S Cycle Gear Drive Cams for Harley-Davidson Twin Cam 88 Engines - Manual (Page 2)

INTRODUCTION
The S&S ® gear drive cams offer many advantages over the
original cam chain drive system:
G Reduced maintenance. There are no chain guides or shoes to
wear or replace and no debris from wearing guides or shoes
in your engine oil.
G Consistent cam timing. Cam gears are keyed with a light
press fit. Chain and tensioner induced variations are no
longer a problem.
G Eliminating the chains and tensioners eliminates excessive
side loading of cam bearings.
G Critical sprocket alignment is unnecessary. Use of precision
machined spacers is eliminated.
G Maintain accurate valve timing when using high
performance valve springs with higher spring forces.
G Higher cam lifts can be used without decreasing cam base
circle. Gear driven rear cam rotates in opposite direction
from chain driven cam. Lobes on front and rear cams never
point toward each other, allowing increased lobe height.
COMPATIBILTY NOTES:
G S&S Gear Drive Cams are not compatible with camshafts
designed for the stock chain cam drive. S&S Gear Drive Cams
must be used with S&S gear drive camshafts.
G Except for the 510G, the gear driven camshaft kits are not
compatible with stock pushrods or valve springs. S&S
adjustable pushrod kit 93-5095 is recommended for engines
with stock length cylinders. Longer pushrods are available
for engines with longer than stock cylinders. See the S&S
catalog for pushrods and valve springs.
G S&S Camshaft Installation Kit 33-5163 is strongly
recommended when installing S&S gear drive cams. The
kit includes gaskets and bearings required for installation,
but does not include oil pump
o-rings.
All S&S gear drive cams except for the 510G require that the
stock valve springs be replaced with high lift spring kits.
Some high lift spring kits require clearance checks and may
require cylinder head modifications to prevent contact
between top collar and valve seal, and to achieve correct
installed height. See the instructions with your spring kit for
exact specifications.
G When using S&S gear drive cam shafts with stock Harley-
Davidson pistons, valve-to-piston clearance may need to be
checked. See Chart 2.
G If stock Harley-Davidson heads are decked, valve to piston
clearance must be checked. If insufficient clearance is found,
valve pockets must be modified.
G When using S&S pistons with S&S heads which are
unmodified or have been decked no more than .062", no
additional valve to piston clearancing will be required.
* Using unmodified heads with .045" head gaskets.
OK No Clearancing needed.
1 Valve to piston clearances must be checked.
2 Valve pockets in pistons must be modified.
INSTALLATION
1. Remove Cam Chain Drive
NOTES:
G Changing camshafts and cam drives in Twin Cam 88 engines
is different than in previous engines. Procedure requires use
of a hydraulic press and some special tools. Installation
should be done by an experienced mechanic with access to a
factory service manual and all required tools.
G Tighten all fasteners to correct specifications and in order
described. Always use an accurate torque wrench.
Incorrect installation can cause engine damage not covered
under warranty.
Failure to install components correctly can result in sudden
engine seizure. Engine seizure may result in serious injury to
motorcycle operator, passenger, or others.
2
Chart 2
Chart 1
Specification for S&S ® Gear Drive Camshaft for Harley-Davidson ® Twin Cam 88 ® Engines
Cam
Valve Timing
Valve Duration
Valve
Centerline Lift @ TDC
Name
Open / Close
Lift
Intake Exhaust Intake Exhaust Intake Exhaust Intake Exhaust
510G 20°/ 38° 52° / 20° 238° 252° .510" 99° 106° .187" .179"
570G 20°/ 40° 55° / 20° 240° 255° .570" 100° 107.5° .187" .179"
585G 20°/ 45° 60° / 20° 245° 260° .585" 102.5° 110° .186" .179"
625G 20°/ 55° 60° / 20° 255° 260° .625" 107.5° 110° .189" .184"
640G 25°/ 60° 65° / 25° 265° 270° .640" 107.5° 110° .228" .214
Valve to Piston Clearance Chart
Stock Harley-Davidson ® Pistons*
Head Cam
Style 510G 570G 585G 625G 640G
Stock OK OK OK OK 1
S&S 79cc OK OK OK 1 1
S&S 89cc 2 2 2 2 2
CAUTION
CAUTION
WARNING