Internal combustion engine

An internal combustion engine, having at least one cylinder, comprising:

• an axially displaceable cam shaft;
• at least two cams fixed for rotation together with the cam shaft;
• the at least one cylinder having an intake and an exhaust valve, each valve being operable by a cam-activated push rod;
• the intake valve being operable by a first multiple lobe cam having at least two push rod activating lobes, one of the lobes having a first eccentric circumferential surface relative to the cam shaft axis for periodically opening and closing the intake valve over a first timing range, and the other of the at least two lobes having a second eccentric circumferential surface relative to the camshaft axis for periodically opening and closing the intake valve over a second timing range, the cam further having a transition surface on which the push rod can easily slide between adjacent lobes;
• the exhaust valve being operable by a second multiple lobe cam having at least two push rod activating lobes, one of the lobes having a third eccentric circumferential surface relative to the cam shaft axis for periodically opening and closing the exhaust valve over a third timing range, and the other of the at least two lobes having a fourth eccentric circumferential surface relative to the camshaft axis for periodically opening and closing the exhaust valve over a fourth timing range, the cam further having a transition surface on which the push rod can easily slide between adjacent lobes;
• and,
• the respective lobes of the multiple lobe cams being selectively positionable to engage and activate the push rods through axial displacement of the cam shaft during operation of the engine, whereby the timing ranges of the intake and exhaust valves may be selected, without interfering with operation of the engine, to improve efficiency and gas mileage at different engine speed ranges.