The sludge trap caps had already been cleaned.  It is important that the mating faces are inspected to ensure that they are not corroded  or deformed.

The larger big end caps are shown in the back row.  The main bearing caps, at the front, show the rear unit on the left, front on the right, with the highlighted (O) being the centre main cap.  This latter cap is the same as the others but has a slightly longer bolt to span the larger centre bearing.

All of the nut and bolt threads were cleaned using 'loose' taps and dies.  It is important that no metal is removed but that the threads are clean to ensure easy assembly.