A fancy drawing board. The thing you have to keep going back to when stuff doesn't work.
Sometimes, it shows problems as proved by these sectional views
As it stands, the only way to create the block's water jacket is with a cored casting. Considering the amount of metal that would have to removed for the other features from a large, expensive, solid block, that would be a sensible way to proceed. Making both parts of each main bearing cap bolt in would make machining them and the block easier.
As modelled, there's no good way to get the curved ports in the head without another casting. Changing them to angled ports and throats would remove this need, although continuing the water jacket to surround the combustion chambers would put it back. The head needs to 5mm longer at each end to prevent the headbolt counterbore breaking out. This would make the nose on the cam boxes redundant and make the water jacket surround the end cylinder liner if carried into the block.
There are no crank or rod bearings, although there is space for them. Nor is there any oiling system; I'd probably use an external pump for the main and cam bearings, driven off the water pump belt. Splash oiling for the conrods and pistons. The water pump is currently empty, and needs some serious thought to make it work.
I modelled the sump using surfaces for some practice and to make it look like a stamped sheetmetal part, but if actually building this thing I would hollow it out of a block or add it to the casting list.
It's easy to
say that this would be an electronically managed engine, but scale injectors are an entirely different matter. Ignition systems are available. I've a friend who built a 180cc OHV V8, and getting the carburation even working, let alone well, was the hardest part of the build.
I suspect it will need domed pistons, instead of the flat top ones shown, to get enough compression to actually work.
It has a 25mm bore on 35mm centres, and a 30mm stroke