The what, why, and how these engines have remained so unchanged from their antiquated designs and event turning abilities is certainly a good discussion subject for airplane builders, owners, pilots, and other interested parties.
Some relevant points that immediately come to mind in such a discussion include the following:
MOST CERTIFIED AIRCRAFT ENGINES………
use no seals on the valve stems
use piston/ring design and metals from an era gone by
use carburetors to vaporize the fuel. If fuel injected, these systems could be called “dribble type nozzle systems”
use ignition systems that have no timing advance/retard capability(with the exception of impulse magneto couplers and retard breaker systems designed to assist in starting only)
To cite some examples of the ramifications of such items, please note that:
Unsealed exhaust valve stems cause an increase in crankcase pressure as does the antiquated piston ring designs.
These two leakage events are the major cause of oil leaks and oil carried as a vapor from the engine drag tube.
The lack of valve stem seals on the intake valves allows the lower pressure within the intake manifold to draw engine oil into the cylinders to be consumed during combustion
With all of the above, by using the correct propeller to load the engine, adjusting the fuel mixture manually, presetting the timing of the ignition and insuring the temperature of the engine is correct, and targeting these events to be optimized for operating at a specific R.P.M. ..with the exception of some oil loss and consumption, little help in performance can be realized due to the fact that the engine is not generally used “like a car”, with many frequent accelerations and decelerations.
I still love the smell and sound, especially from an oil burning radial----------------Dick B.