S&S Cycle 2006-Up Gear Drive Cams for Harley-Davidson Twin Cam 88 Engines - Manual (Page 2)

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S&S® Gear Drive Camshaft Specifications for Harley-Davidson Twin Cam 88® Engines
Cam
Name
Valve Timing Valve Duration
Valve
Lift
Centerline Lift @ TDC
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"
Chart 1
INTRODUCTION
The S&S® cam gear drive offers many advantages over the original cam drive system:
Reduced maintenance. There are no chain guides or shoes to wear or replace and no debris from wearing guides or shoe in you engine.
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Consistent cam timing. Cam gears are keyed with a light press fit.
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Eliminating the chains and tensioners eliminates excessive side loading of the cam support plate bearing surface.
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Critical sprocket alignment is unnecessary.
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Maintained accurate valve timing when using high performance valve springs with higher spring forces.
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Higher cam lifts can be used without decreasing cam base circle. Gear driven cams rotate in opposite direction from the chain driven cams. Lobes
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on the front and rear cams never point towards each other, allowing increased lobe height.
COMPATABILITY NOTES:
S&S Cam Gear Drive is not compatible with camshafts designed for the stock style chain cam drive. S&S Cam Gear Drive must be used with S&S gear drive
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style camshafts.
2006-Up gear driven camshafts kits 510G, 570G and 585G are compatible with stock 2006-Up valve springs. Due to the change in lift from the cams, new
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pushrods are required during installation. 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.
S&S camshaft installation Kit 33-5240 is strongly recommended when installing S&S cam gear drive. This kit includes hardware, gaskets and bearings
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required for cam installation, this kit does not include oil pump o-rings.
All S&S gear drive cam shafts except for the 510G, 570G and 585G required that the stock valve springs be replaced with high lift spring
kits. Some high lift spring kits require clearance checks and many require cylinder head modifications to prevent contact between top
color and valve seal, and to achieve correct installed height. See the instructions with your spring kit for exact specifications.
When using S&S gear dive cam shafts with stock pistons, valve to piston clearance may need to be checked.
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See Chart 2.
CAUTION
Valve to Piston Clearance Chart Stock Harley-Davidson® Pistons*
Head
Style
Cam
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
*Using unmodified heads with .045” head gaskets
OK No Clearancing needed
1- Valve to piston clearance must be checked.
2- Valve pockets in piston must be modified.
If stock heads are decked, valve to piston clearance must be checked. If insufficient clearance is found, valve pockets must be modified.
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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
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required.
Chart 2