Have an E1 here with a fuel issue.
Pump will fill the carb bowl at an idle and run (abit rich). But the bowl then drains at about 4000 rpm.
Anyone know what could be happening here?

Fuel pump may be defective. It may not put out enough volume for 4,000 RPM operation

Or, there may be an air leak into the fuel hose during high suction. I'd start there:
* go around and tighten the hose clamps at the tank, at the filter, at the fuel pump
* Inspect the fuel hoses and hard lines for any trace of dripping. A tiny spot of gasoline means it is leaking a tiny bit

So the problem was he had next to no fuel in the tank :')
So with the fuel we sucked out of the tank the sediment filter (before the fuel filter) was full of muck and grains of sand D:.
Now the car won't start at all..... Although it gets fuel every time we start to crank it over..

So I'm thinking it has blocked jets in the carb or something like that??
Would you have a diagram of the carby.
Also is that a stock carby?

Yes, that's a stock carburetor for Japan Datsun 320 and for USA Datsun 320 - NIKKI. Sorry I don't have a diagram

check the old ratdat.com or olddatsuns.com they may have diags