"Dished or recess top pistons are not performance oriented. Engine
performance is somewhat proportionally related to compression ratio"
Somewhat?!?! I think Otto just turned over in his grave. Compression ratio
is directly the most important aspect of theoretical engine performance. A
engine with infinite compression ratio would make infinite amounts of
horsepower(given no pumping losses frictional losses ect). Unfortunately
engine design is a study for engineers not economist(otherwise we would all
drive Insights with the exact same color and options list, and they would
cost $10). Engineering is a business of tradeoffs. You have to balance the
need to run high compression motors with the realization that engine
components will break at high compression and predetonation will occur.
Therefore if you are cramming 400cc's more air into the same size combustion
chamber (R16) with a shaved head there is a possibility you need to use the
dished pistons to bring your CR into a reasonable compromise.
A second point that I will make is drop in price is not equivalent to a
decrease in quality. If you believe the opposite is true you must also
believe there is no such thing as a bargain. I suggest you shop only at
Sachs Fifth Ave, and you sell your Datsun for a Healy.
I doubt these H20 parts have changed at all since they were first designed
in the 60's, for use in our cars. Metallurgy has actually improved greatly
since that time. I would not be surprised to find that the quality of the
castings have improved.
Everything else a side, we can not stare at our computer screens and
theorize what parts are better and why, and expect to come to a conclusive
answer. If someone sends me a brand new H20 part and the identical brand
new U20 part I will take it to the lab, and run some test. Maybe then we
will determine which is the better part, in MY not so expert opinion. I
believe I will probably conclude both parts are of inferior quality. On the
other hand we can just give these parts a try, hope they hold together and
be happy knowing the inferior parts are strong enough for our demands.
Ian Miller
66 1600 (stroked)
U20 pistons
H20 crank
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