Do you have any idea about part inside? I am unable to sketch without understanding it.
The valve body that you are modelling is for an exercise only and may not be technically correct for an actual valve body.
The area that you have highlighted would contain the internal workings of the valve, probably a gate or butterfly style of valve.
Search Google Images for "Gate Valve" or "Butterfly Valve" to get an idea of what might be in there.
Could you expand a bit on what you require? The dimensions needed to model this part appear to all be there.
What will be the function of inside part?
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