Big end

From the sound of that motor, I'd say yer big end's gone, mate.

Except in the case of the largest 4-6-2, not yet in contemplation, use of two [outside] cylinders only was decided on for the following reasons:— […] 2. The split inside big end is a source of trouble at high speeds and powers unless exceptional integrity of maintenance can be guaranteed.

Oil is carried from the big end to the small end by a centrally drilled oil hole.