Will this cause low oil pressure

[Ollie]

After replacing my ZEUS timing gears with standard LR timing belt, I had a low oil pressure warning light on at idle.
A few hundred miles later I had a rumbling engine.

I've stripped the engine out and the main and big end bearings will need replacing. The piston bores look OK though.
Now, how did this happen :-k

At the front end of the engine block, there appears to be two core plugs that block the oil system.
I think that ZEUS as part of their conversion tap a thread into it and place an oil screw in their to feed the ZEUS gears. When I replaced these gears, I didn't 'plug' this hole, (2 in the picture). One other thing I did was to put a new oil pump on.
Soooo, could this umplugged hole have caused the problem? Can new oil pumps be 'duff'?

Here's a picture;

[Range Rover Blues]

|WOW, that's a big hole in the middle.  the top one looks like it runs form the camshaft which should be runing in oil at pump pressure.  Where is the bottom one fed form?

Anyhoo, that hole looks a bit too biug to keep the oil back, were they covered when the Zuess gears were on there?

I'd have said that the holes needed plugging to stop oil contaminating the new belt too.

Are the Zuess gears lubricated total loss (is the oil recovered or wasted).