Crankshaft Oil Seal

Adapter/Carrier for 948, 1098, 1275 and 1300 BMC engines31

mainseal Mini Cooper
Stage 1
        Remove the flywheel, back plate, sump and the half-round cover, secured to the block by 3 bolts, above the main bearing cap (MBC). Carefully clean up the rear block face area adjacent to the MBC (Fig. 1 A); removing all traces of gasket, burrs, etc.; also the outer, horizontal edge of the flywheel mounting flange on the crank. This is where the new oil seal will seat; it will need to be checked for damage and carefully polished smooth with wire wool or fine emery.

        Remove the
MBC, clean thoroughly and remove the shell carefully. Looking at the MBC, you will see that (in the case of the 948/1098) the end face (Fig. 2 B) is not machined, it having been left  as cast ; consequently the height of this end face from the block will be uneven and variable. In order to ensure an oil-tight seal, you will need to establish a constant dimension of 11 MM from the block to this end face on the MBC. The same is required of the 1275 with its finished face. This must be both flat and square to the block (Fig. 3 C).

triangulated part(TR) of this kit is 11 MM thick, and when screwed to the block, its outer face MUST be level with the end face  B of the MBC throughout its length. This part of the fitting process is the longest, and requires a good deal of accuracy, as it is essential for the complete sealing of the unit to the engine. Experience has shown that the 11mm dimension is already fairly consistent on production engines, and the adjustment may well not be required; however, should it be needed, this measurement can be achieved either by surface grinding or very careful filing- either way ACCURATE measuring is essential.

        The silicon sealant in this kit will accommodate a small degree of tolerance in the dimensions, but it will NOT seal large gaps or irregularities against the engine oil pressure at this point.NOTE: In the very unlikely event of the height(C) already being less than 11 MM, you can remove up to 1 MM from TR.
Having completed the above, refit the MBC permanently (not forgetting the shell!); temporarily fit the section TR to the block with the three socket head screws and check that the back plate will pass over it; some careful filing may be required to either back plate or TR.

Stage 2
        Apply a
coating of sealant to the mating faces of TR where it meets the block and the MBC, but do not use a         gasket. Secure to the block, ensuring that it sits snugly against the MBC faces (Fig. 4 D).Refit the engine back plate NOW.
Separate the two halves of the circular carrier by unscrewing the two 4 MM socket screws in its periphery. The upper half(UH) is held to TR by the three 4 MM X 10 screws, access to which is through the bolt holes in the flywheel mounting flange. Use sealant between these faces and fit; tighten the screws evenly, to about 5 ft-lbs torque, ensuring that the edges of UH and TR are aligned at the MBC (Fig. 5). Put a coating of sealant around the oil seal seating area of UH and of the lower half(LH); on the back face of LH, into and around the groove and on the ring joint faces and MBC end face; in fact anywhere there is a joint face.
        Lubricate the oil seal lip with a little oil or grease, packing the back of the seal lightly with grease. Ease it over the flywheel boss and into the alloy carrier UH. Push on the LH, taking care with the sealant and screw the two halves together. Apply some more sealant around the joint between LH and MBC, just for good measure. Allow the sealant to cure for at least 8 hours before running the engine.

Additional instructions for 1275 and 1300 engines
        When refitting the flywheel (Marina, Ital or Midget), space it away from the boss with the 3.5 MM (1.5 for the midget) spacing ring in the kit. There are two different types of flywheel, the difference being in the depth of the register recess in the back. Measure it carefully; it will most likely be about 5 MM, in which case all is good. If it measures closer to 9 MM, then you will need to have it machined down to the 5 MM depth (no less) in order to miss the seal carrier.
        Failure to check and remedy the above will result in the flywheel locking up against the seal carrier.
        The above mentioned spacer is NOT needed when using the modified 1098 Minor flywheel; as is used with the 1098 gearbox conversion, but IS required with the Midget 1275 flywheel. (spacer ring is only 1.5 MM thick for Midget).

        In addition, it is important that:
1.    The front engine breather is not blocked and is offering no resistance to flow. It is best to cut the canister in half vertically, remove the probably sludgy remnants of filter gauze and weld back together (empty), after thoroughly cleaning out the unit.

2.    Ensure that the front breather is connected correctly, either to the brass stub on the carburetor or to the manifold breather valve; whichever is right for your engine layout.

3.    The pipe from the front canister must be free from obstructions, not split or cracked and of a minimum internal diameter of 5/16". If in doubt, use an original equipment hose from Austin Rover.

4. The rocker cover on the 1275 engine should not have a breather tube coming out of the top like the 1098; it must be fitted with the type using a black plastic cap, through which the engine breathes.

5. Newly rebuilt engines can experience excessive piston  blow-by , causing a pressure build-up in the sump, leading to oil being forced past even this sealing arrangement. If this appears to be the case, try adding an additional, temporary vent via the mechanical fuel pump hole in the block (so long as it is not already being used for the pump!).

6.. Failure to observe the above could well cause your engine to leak oil past the new sealing arrangement,
      due to high internal
oil pressure.