Wayne Cook wrote:

The way a Detroit works is it's got a Roots blower on the intake and
there's air intake ports in the sides of the cylinder sleeves. Thus
when the piston is all the way down the blower pushes the exhaust out
the valves in the head and makes it ready for another cycle.

In other words Detroit are 2 stroke diesel engines compared the most
others being 4 stroke.
All the Detroit Diesels I know of used valves, only, no ports. The huge
Ferry-Morse Diesels used ported cylinders. Detroit Diesel is not the
only outfit making two strokes, and now not all their engines are two
stroke, either. The legendary 6-71, 8V92 and others of that series
all used 4 valves/cylinder, pushrod-driven rocker arms, and a Roots
blower for ventilation.

I've never figured out how the rings could survive passing over intake
and exhaust ports on a Diesel without requiring a lot of maintenance.
It just seems like they'd pick up a wear pattern that would compromise
the sealing.

Jon