Can anyone help me in modeling this object?

I modeled the bottom bore part.

Now I want to model the top part of it. I have many reference pictures. But I cannot find a good top view of the layout of the engine (marked in green in top left).

An help?

Does a gasket go there? If so, maybe you could find an image of that?

I tried to find gasket, but the gasket was more square and not like this :frowning: