Model year specific installation warnings – Zipper's Performance Red Shift Cams TC User Manual

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Model Year Specific Installation Warnings:


1.) Camshaft to Case Clearance –

Early Twin Cam engines were produced with

significantly more material in the bottom end castings, resulting in

interference issues with even the smallest bolt-in camshafts.

Zipper’s developed a cam relief tool in early 2000 to properly machine

clearance into the engine case, when it was apparent that higher lift cams

would not bolt right in. The nice thing about the Zipper’s tool is the machined

chip size, since the system uses a carbide tool bit, all of the cleanup is generally

larger chips of material. Although a die-grinder will create the proper

clearance, any grinding tool will produce extremely fine debris and grit as it

cuts. Fine grit is more difficult to clean up, and is more likely to embed itself

into the powder coat inside the cam chest, because of the heat the particles of

grit carry. Some of this grit will not release from the powder coat until the

engine is running at full operating temperature.

2.) 1999-2000 Spline Drive System -

If you have an early 2000 or earlier model engine and wish to retain the stock

keyed type drive cam, we strongly urge you to purchase an aftermarket drive gear. Stock drive gears use a narrow key

channel, which has known to fail and spin on the camshaft when used with performance cams. This can cause

extensive damage to the top end components if this failure occurs with the valves open. Drive gears with a longer key

channel can be purchased through the Zippers Sales Department.


1999-2006 Rear Camshaft Endplay -

If you are installing an updated rear cam roller bearing from H-D®, be sure to

check cam endplay spacing as per the factory Service Manual. This bearing was designed specifically for the splined

type camshafts, but can be installed on keyed type camshafts by installing an additional hardened spacer washer (H-D

P/N 8986) on the cam sprocket side of the bearing.


1.) Cam Cover Clearance –

When installing either a gear drive system, or Red Shift Dual Piston Cam Chain Tensioners,

you must create clearance on one of the casting ribs inside the cam chest cover. Simply remove one support fin with a

die-grinder, taking it down flush with the inside of the cover.

Starting in 2009, the cam chest cover no longer is produced with support ribs, and no additional clearance is required.