"By all means, I would be interested in reading some "Pent-head
Propaganda".grin"


Info on pent head design:

http://www.speedoptions.com/articles/2327/

"The modern, now almost universal low pent roof, narrow valve angle style
four valves per cylinder combustion chamber, was designed, or re-invented
etc., by Keith Duckworth of Cosworth engineering in 1966 for the incredibly
successful Cosworth DFV Formula One engine. This engine dominated world
Formula One racing from 1967 to 1983 and produced one hundred and fifty-five
world championship victories. The advantages to this type of combustion
chamber are focusing the compressed charge to the spark plug, raising an
engine's knock threshold and the ability to run higher compression ratios.
Additionally, higher port runner angles and of course more valve curtain and
port area are also major advantages."

http://hometown.aol.com/dvandrews/timing.htm

"Note how little advance a four valve, pent roofed combustion chamber needs,
this is because of the very short and equal length flame paths from the
centrally placed plug promoting a very fast burn. Engines with a faster burn
time have a much higher RPM potential, the faster the burn, the less advance
requirement, and therefore the fewer problems at high RPM. This is why Grand
Prix engines have many small cylinders; these have small combustion chambers
that have very fast burn times, allowing much higher RPM than engines with
fewer large cylinders. "

http://www.shotimes.com/SHO3gas.html

"...Yamaha's 4-valve pent-roof combustion chamber with its centrally located
spark plug is about near-perfect, which means it can extract more power out
of the burn than a poorly designed combustion chamber. Some of the venerable
small and big block high compression V8's of yore had absolutely rotten
combustion chamber designs, making their octane requirements higher than the
more efficient designs of today. Additionally, modern engine management
systems are able to detect trace knock and manage spark timing much more
effectivey than older systems with fixed mechanical and vacuum advance
curves."

http://www.schubeckracing.com/Anewge...aceengine.html

"The chamber of choice of the Japanese "super" bikes (the Kawasaki Ninja,
the Honda Hurricane, the Yamaha FZR, etc.) and Indy and Formula 1 engines,
the pent-roof permits a flat (or even concave) piston, a cylinder head that
is only slightly domed, and a centrally placed spark plug. The effect is
that the fuel and air mix are ignited rapidly because the mix is
concentrated tightly around the plug. That allows higher compression ratios
to be used with less fear of dreaded detonation-the charge quickly burns
before the detonation. There's another benefit of the pent-roof design.
Because the mixture is inflamed quickly, heat loss to cooler parts of the
head is cut down so more energy is available to push the piston down. And
the flatter combustion chamber offers less material (124cc to the Hemi's
167cc of combustion chamber) to further impede heat-energy loss.
Additionally, a pent-roof design allows for generous squish areas-flat
sections of the chamber roof where the near contact of the piston to the
head creates turbulence."

jon