Far square tumble flow engine

A replaceable cylinder head assembly for a successive inlet valve engine, the assembly comprising:

• a first inlet to a first parallel port of a combustion chamber of the engine;
• a second inlet to a second parallel port of the combustion chamber, wherein the first of the inlets facilitates angled, substantially non-perpendicular tumble flow of a spark-ignited air-fuel mixture to the combustion chamber in advance of the mixture through the second inlet;
• and
• a restriction between the at least two inlets to increase a velocity of the mixture to one of the inlets in contrast to the other of the inlets.

A method of generating tumble in an engine for use of a spark-ignited air-fuel mixture in a combustion chamber thereof, the method comprising:

• directing the mixture toward the combustion chamber;
• separating the mixture into first and second inlets coupled to first and second parallel intake ports of the engine in advance of the combustion chamber;
• successively delivering the fuel to the ports with a valve assembly comprising the inlets to generate a tumble flow of the fuel into the chamber;
• and
• restricting the mixture at a location between the first and second inlets to increase a velocity of the mixture into the second inlet in contrast to the first inlet.