Technical Data

A

Cylinder block

Material: Cast iron

Finished size:

Grade A 2.8746/2.8750

Grade B 2.8750/2.8754

Cylinder head

Standard

Combat

Material:

RR 53 B

RR 53 B

Valve seat angle:

45°

45°

Inlet port nominal dia.:

1 1/8 in. (28.573 mm)

1 1/8 in. - 1 1/4 in. (28.575 - 31.75 mm)

Ex. port nominal dia.:

1 1/4 in. (31.76 mm)

1 1/4 in. (31.75 mm)

Ex. ring thread size:

1.997 in. x 14 T.P.I.

1.997 in. x 14 T.P.I.

Camshaft

Standard

Combat

Material:

EN 32 B

EN 32 5

Max lift-

Inlet

0.332 in. (8.389 mm)

.390 in. (9.906 mm)

exhaust:

0.322 in. (8.389 mm)

.346 in. (8.788 mm)

Base circle dia.:

.885 in. (22.479 mm)

.906 in. (23.012 mm)

Bearing journal dia.:

.8735 in. (22.187 mm)

.8735 in. (22.187 mm)

Camshaft bushes

Pre 1972

1972 Onward

Fitted l.D. (Left bush):

.8750 in. (22.225 mm)

.8750 in. (22.225 mm)

Fitted l.D. (Right bush):

.8750 in. (22.225 mm)

.8750 in. (22.225 mm)

Tappets

Material: Cast iron Grade 1 4 - stellite tipped

Push rods

Material: Heat treated Dural tube "B" or "S"
Inlet - assembled length: 8.166/8.130 in. (207.41 6/206.466 mm)
Exhaust-assembled length: 7.321/7.285 in. (186.053/185.039 mm)

Rockers

Material: EN33
Rocker ratio - inlet: 1.13 :1
Rocker ratio - exhaust: 1.13:1
Bore diameter: 0.4998/0.5003 in. (12.694/12.708 mm)
Adjuster thread size: 9/32 in. x 26 TPI. Whit Form

Rocker shaft

Diameter: .4988/.4985 in. (12.694/12.669 mm)

Valve (tappet) Clearances (engine cold)

Inlet: 006 in. (0.15 mm) (Commando); .008 in. (0.2 mm) (Combat)
Exhaust: .008 in. (0,2 mm) (Commando); .010 in. (0.25 mm) (Combat)

Valve Lift

Standard

Combat

Inlet: .375 in. (9.525 mm)

Inlet: .441 in. (11.21 mm)

Exhaust: .375 in. (9.525 mm)

Exhaust: .391 in. (9.931 mm)

Valve duration:

Standard

Combat

(excluding ramps)

152°

164°

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