how bad is bad, what happens when oil pumps wear? Options

[worn]

I am rebuilding a 911 engine for which metal parts went into the oil pump. The impellers and case show some scoring and I will probably be replaced. Still it begs the question: how bad can it be? The scoring between impellers can be honed flat to prevent more galling. The scores between the impeller edges and the case obviously will allow oil to leak past. To that I ask - so what? I can readily imagine a reduction in output and therefore oil pressure. On the other hand it is hard to imagine a really dramatic reduction in pressure due to oil leaking past/through some scratches.

Do scratches tend to propagate wear in the pump?

When oil pumps fail, how do they fail.

Thanks folks, and note I am not asking whether or not to replace a pump, I am asking what happens when you don't. Or how bad does it have to be before it matters.