Reply to "Wide and Flat Torque Curve"

The cross-sectional area of the port's runner is reasonably small and constant along the length of the runner, the extra volume is gained via a large valve pocket. The large valve pocket slows the velocity of the gases so they can make the turn into the valve pocket and distribute evenly around the back side of the valve.

The sharper the turn, the more the gases must be slowed down. High ports turn less sharply, low ports turn more sharply.

Sizing the port has more to do with powerband than velocity. The gases in a high performance motor gain velocity as the result of piston speed, not port cross section. If you reduce the size of the port too much, to gain gas velocity at low piston speeds, the port will act as a restriction to gas flow at higher speeds, and the gain in inertial energy at low speeds is usally not enough to perform any usful benefit. That is as per Mr. Morgan.

As far as I'm concerned, discussion of port height is more important than the usual discussion of air velocity. This is one good example, where a high velocity port looks like a lower velocity port because of the large volume number. But the large volume is the result of a large pocket, not a large cross-section runner. The large pocket was needed due to port height!

Another aspect of the design, the ports are very non-turbulent, air flow keeps increasing as the valve keeps opening, all the way out to 1" valve lift! Mr Morgan says the exhaust port is the best "low port" he's ever designed. That's saying a lot. This aspect is also more crucial than the usual "small ports" and "high gas velocity" sales talk.

One last point I'd like to make, the price of these heads aren't cheap, but that is because Scott refuses to have them cast in China. He has them cast domestically in Australia. I think a lot of us would give him kudos for that.

Now back to that torque curve ... isn't anyone besides me impressed?


-G