"By all means, I would be interested in reading some "Pent-head Propaganda"."
Info on pent head design:
formatting link
"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."
formatting link
"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. "
formatting link
"...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."
formatting link
"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