Well, I'm not trying to make this any kind of debate, of course, but, in a t-shirt, the timing cover will be solid latex. Also, by itself, it could end up looking like a bra on those of us without rock-hard pecs. How about a whole engine drawn similar to Graybeard's image, but not cutaway. If the engine, circles and lettering are all independent from each other over the background, there might be enough open area to be comfortable.
This effort could be called "Goingt Nitty." (Thanks to member Nitty, wherever he is, for making some very nice BSA patches some years ago.)
Richard L.