Mk. I and II (SERIES BN7 and BT7)


Section No. AAA.1
Accelerator shaft bushes
Section No. AAA.2
Fitting cylinder liners
Section No. AAA.3
Throttle control linkage


The engine is the same as that fited to Series BN6 cars except for dimensional differences.

Section AAA.1


The oil pump fitted to early engines is of the Hobourn Eaton rotary vane type, the service procedure for which is detailed in Section A.8. Later engines, however, are equipped with a gear type pump and instructions for servicing this type of pump are given below.

Fig AAA.1 Components of the oil pump.
Fig AAA.1 Components of the oil pump.

Removing the Oil Pump

  1. Remove the sump and pick up strainer.
  2. Take off the nuts and spring washers from the three studs which secure the oil pump assembly to the crankcase, when the pump can be withdrawn.
    If the pump is removed with the engine still in the car, the drive shaft will be free to disengage from the camshaft, and care must be taken to prevent it falling out. Note also the thrust washer fitted on the drive shaft above the gear.

Dismantling the Oil Pump

  1. Mark the flange and pump body to assist reassembly and remove the four retaining bolts with their spring and plain washers.
  2. Separate the pick-up from the pump body, withdraw the drive gear and spindle and the driven gear from its fixed spindle.
    Thoroughly clean all parts in petrol or paraffin and dry off.
  3. Replace the gears and check for wear. (a) The radial clearance between the gears and the pump body should not exceed .00125 in. to .0025 in. (.032mm. to .063mm.). (b) Check the clearance between the gears and the end cover by placing a straight edge across the pump body and checking with a feel guage. End float should be between .0005 in. and .002 in. (.013 mm. and .051mm.).

Renew worn parts as necessary. The pump driving gear is a press fit on its shaft and is keyed in position. The spindle should protrude .312 in. (7.94 mm.) from the gear face.

Replacing the Oil Pump

Care should be taken to see that the abutting faces of the cylinder block and the pump are clean before replacing and that the joint washers are in good condition. Insert the pump from below ascertaining that the driving gear is in mesh with the gear on the camshaft. Secure the pump with the three nuts and spring washers. Replace the pick-up strainer and sump.

Section AAA.2


The dimensions required for the fitting of cylinder liners to the 2.9 litre C type engine are given below.

These dimensions should be used in conjunction with the removal and fitting instructions given in Section A.33..

Cylinder bore and liner dimensions.
Cylinder bore and liner dimensions.

Section AAA.3


To prevent the throttle linkage becoming strained and the throttle levers from becoming loose, the linkage may be adjusted to allow the toe board to act as a positive stop to the accelerator pedal when the throttles are fully open.

Slacken the pinch bolts on levers A B and C (Fig. AAA.3). Place a wooden block 2 1/2 in. (63.5 mm.) thick between the pedal and toe board; push the pedal down to retain the block against the toe board. Adjust lever C to obtain a clearance of 1/16 in. (1.59 fmm.) between the lever and the body flange as shown at X (Fig. AAA.2). Tighten all pinch bolts.

Release the pedal and then re-check the setting.

Fig. AAA.2. Throttle Control Linkage Adjustment
Fig. AAA.2. Throttle Control Linkage Adjustment