Thanks for the response. The problem with installing a fluidmaster is that on this type of toilet it is impossible. It has a built in cavity for the water inlet.
I have an old case 50 toilet. I have replaced the ballcock etc. Does anyone know how to adjust the water inside the tank. There are two different adjustments. Water inlet and past the ballcock is a regulator. This model has been discontined 40 years ago. Thanks for any help. :)