How many L of oil?

My engine is very loud and tapping its that loud i can hear the valves opening and closing.Ive been told my exhuast manifold is missing a thread and the gasket has gone. But some times the sound seems to be coming from the rocker cover and some times the inlet manifold i have tryied 2 lots of waynes tapped treatment with no luck drove 200 miles after adding it then left it a few days added more and still no luck. Temp is fine and water is fine and oil is fine. I was thinking of adding castrol gtx 10w-40 for high mileage cars. My car has hit 80k today just wondering how many L of oil do i need ? Its a mg zr 1.4 petrol.

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