[olddog]

I have often thought about the forces required in a valve train at high rpm. If you added a set of springs in the lifter gallery that pushed down on the push rod, you could design that spring to be able to hold the lifter on the cam shaft at say 8000 rpm, higher if you want more rpm. This results in the valve spring only having to do work on the valve, keeper, and rocker arm. I would think this would allow for quite a few more revs. The FE design with the push rod going through the intake would take some options away on how to do this, or at least make it a bit more challenging.

Often when you have a good idea, someone else has already done it. I never saw such an engine, but I have not seen every engine.

Anyway that is my free tip, if you want to shoot for some more rpm.