@peemee That’s a really nice design! I have a timing chain in my Toyota Avensis and it’s pretty darn nice to have.
I remember Volvo making the B200F engine in the second half of the 1980s, and that had the explosion chamber in the actual piston head. If the timing belt broke, you also lost the valves and the whole engine head, really.
That design didn’t live long, needless to say.