Rockerbox breathing

[Greenfield]

Ratio describes adding a breather hole to a rockerbox inspection cover to improve breathing in a unit single. I wonder whether anyone has experience of this or have any comments to make about it.
I have just unblocked the breather/drain hole in the inner timing cover of my B40 and with the outer cover still not replaced, it's quite noticeable how much air passes through it as the engine is turned over.

[AWJDThumper]

The camshaft breather works well on the smaller unit singles provided the exit from the inner cover is not blocked. The engine's going to force out 350cc of air through the breather every time the piston descends.

[JulianS]

Used a rocker breather on a Starfire a few years ago. (A concentric needle jet fitted)
Did it make any difference?

No not really. It was not a leaky engine in the first place.

It will not compensate for engine wear or a blockage in the timed breather, and remember that an untimed breather will suck as well as blow.

[ANDY HIGHAM]

The timed breather on the camshaft is designed to keep the crankcase at below atmospheric pressure. Adding a breather to the rockerbox destroys this

[Greenfield]

Many thanks. I wasn't thinking of rushing into it particularly as it wasn't original spec. Getting the engine running sweetly is my first priority.