Combined oil trap and dust seal mounted at the rear of the crankcase behind the flywheel. The felt dust seal is shown uppermost and rubs against the crankshaft flange.
|Left and below are the inner views of the two halves. Left, with the felt seal at the bottom, the groove above is the oil trap with drain holes back into the sump. The upper rebate is where the rear crank oil scroll spins. As can be seen, the vertical face is black in this lower section whereas shiny in the following picture. This would indicate that the crankshaft is set slightly higher in the block than it should be. Further investigation required.|
With the engine inverted: this is the upper half of #7 main bearing with the upper part of the end plate still attached. The the curved tube at the bottom of the picture is a breather.
It was found that the spinning flywheel created a reducion in air pressure that effectively sucked oil past the rear scroll. By curving the breather into the air movement generated by the flywheel it was found that the problem was overcome.
|Photographed from above (with the engine inverted); this shot gives the general layout of #7 main bearing, showing the minute tolerances for the oil scroll plus how the felt seal sits. Note also the hollow-ended main bearing studs - the drilling is only about 0.5" deep and is a carryover from aircraft engine development, allowing stretch stresses to be concentrated under the nut rather than near the root.|
Number 4 main bearing cap, shell and shims. Lots of things to note here:
a) main bearings are white metal on shells
b) the brown discoloration in the centre of the shell is not a reflection - measurements need taking to determine whether this is shell wear or oil varnish
c) the lower part of the shell shows evidence of high spots; so the shell may be breaking down
d) the shim edges, which are lined in with white metal, have been damaged by some foreign body rather than by disintegration. Also note the light scouring on the shell.
|A close-up picture of a shim. This is the upper surface with its locating chamfer on the right.|
|This is its other surface denoting it as #4, 'dot' represents 'B' side on this engine.|
|And finally... the crankshaft.|