Tilton 7.25 OT-II Clutches (98-725R) - Manual

The typical production engine has been made to align the transmission good enough for
an OE-size clutch with a single sprung hub disc. These tolerances are not tight enough for a
small clutch with solid discs.
DRIVELINE ALIGNMENT
The bellhousing must be checked to see if it is both concentric (Photo A) and parallel (Photo
B) while bolted to the engine. This is easily checked with a dial indicator mounted to the bare
crankshaft.
Maximum out-of-concentricity is .010" and maximum out-of-parallel is .010".
The following may occur if driveline alignment is not correct:
• Hub spline wear • Cracking of friction discs
• Pilot bearing wear • Loose or failed disc rivets
• Transmission input shaft and bearing damage
If you know your housing is accurate, you can correct block concentricity by using a block
drilling fixture. An out-of-parallel block should have the rear face machined by a competent
machine shop.
FLYWHEEL INSTALLATION
Most cerametallic racing clutches should be used with a step-type flywheel. This step should
be between .098" and .100" tall (Diagram C). Most Tilton flywheels are designed to have the
bolts installed from the engine side before bolting the flywheel to the crankshaft. A retain-
ing lip is used to keep the bolt heads from turning. Crankshaft bolts must be tightened to
manufacturer's specified torque when installing flywheel. Typically, Tilton steel flywheels
with 7/16" bolts require 75 lb-ft with thread locking compund.
RELEASE BEARING INSTALLATION
Make sure of the following when installing release bearing:
• A 44mm (13/4") contact diameter, radius-faced bearing should be used with this clutch. A
52mm radius-faced bearing can be used, but clutch engagement will be quicker and pedal
effort will increase.
• If installing this clutch with a Tilton hydraulic release bearing, follow these procedures:
1. Completely compress the piston/bearing into its hydraulic body. Take all
release bearing clearance measurements in this completely retracted state.
2. Clearance from bearing-to-diaphragm fingers must be between .170" and .230" for a new
clutch. Clearance will decrease as the clutch discs wear.
3. Set pedal stop as described in the Pedal Stop Setup section.
• If installing this clutch with a mechanical linkage, slave-and-fork or many non-Tilton bear-
ing assemblies, less bearing free-play and more frequent adjustments may be necessary.
• Regardless of bearing type used, do not travel the release bearing more than .250" once
the bearing contacts the diaphragm fingers. More travel than this will damage the clutch.
See the Pedal Stop Setup section for information on pedal stops.
MASTER CYLINDER SELECTION
If you are using this clutch with a Tilton hydraulic release bearing, it should be used with a
3/4" master cylinder. Bleed the clutch hydraulics (being careful not to over-stroke the clutch)
prior to setting the pedal stop.
Cross Section Of Flywheel
Photo A Photo B
3/4" Tilton 75-Series Kit - (P/N 75-750U)
See all Tilton master cylinder kits at tiltonracing.com
.100"–.098" Clutch Leg
Mounting Surface
Friction Face
OT-II 7.25" (185mm) Cerametallic Racing Clutches
INSTALLATION INSTRUCTIONS 98
-7
25R
Diagram C
Discs sold separately