Square Four oilways - a new way to block them

[paul.jameson]

I was working on a Mk I front crank today and, as is my practice, I put the crank into the parts washer and applied the pump hose to the drillings. These I make sure are scrupulously clean by means of a variety of tiny bottle brushes. Starting with the hose pumping cleaning solution in through one sludge trap hole all seemed to be ok initially. But applying the bottle brush , there seemed to be a blockage part way between the two sludge trap holes. After a while I found that the blockage could be moved to and fro but it was pretty effective at stopping the flow to No 4 big end when pushed in that direction. Eventually, I found the blockage was in fact a ball bearing but it could not be persuaded out of either of the sludge trap holes. Thinking that it could only have come from the pressure regulator, I eventually got it out of the end of the crank. The diameter is 187 thou so 3/16". Sure enough, that is the diameter of the ball in the Mk I oil pressure relief valve but how on earth did it get into the crankshaft drillings? The offending ball (and crank) is pictured below:

[allan.walker]

Those OPRV's can be problematic at the best of times, in my experience, but the ball finding its way into the oil gallery must be the fault of the previous person who worked on the engine, surely? Has the inner end of the OPRV body been drilled-out at some time, I wonder?

Allan.

[Roger Gwynn]

That's a new one!

[Julian Murphy]

You were lucky.

Scrupulous cleaning saved a wrecked engine.

[simon.holyfield]

Those OPRV's can be problematic at the best of times, in my experience, but the ball finding its way into the oil gallery must be the fault of the previous person who worked on the engine, surely? Has the inner end of the OPRV body been drilled-out at some time, I wonder?

Allan.

Maybe someone reseated it rather too enthusiastically? Or perhaps assembled it ball first?

Whatever it was, well done.