Seems to me that somewhere in the past . . .
Someone developed a four stroke (or diesel)
engine using a sleeve around the piston
as the intake valve
(instead of the stem and tapered seat valves
found in all four stroke engines these days).
Is this true ? ? ?
If you look at how a cylinder breathes . . .
It makes perfect sense.
As the piston moves down on the intake stroke, the cylinder pressure is below atmosphere.
This would tend to force the valve open.
Also, the downward motion of the piston could also be used to move the valve sleeve downward, in effect, reducing the distance the piston would have to travel during intake.
As a rule the intake valve runs a lot cooler than the exhaust.
The rest of the time (compression, combustion, exhaust) pressures in the cylinder are above atmosphere, which would
tend to trap the valve shut.
In addition, the intake and exhaust valve size could be greatly increased (The exhaust would be the only stem type valve required).
Do you for see or are you aware of any problems with this type of cylinder sleeve and valve arrangement ? ? ?