A valve actuation system is described containing a collapsible pushrod device for use in a reciprocating piston machine cylinder such as an engine. The collapsible pushrod device replaces a conventional pushrod. The system can include a driver base, plunger, and a deactivation pin assembly. In normal operation, the pins lock the driver base and plunger together thereby providing regular valve motion. Under selected conditions, the pin assembly controller unlocks the driver base from the plunger. Valve lift is reduced or eliminated. When eliminated, the cylinder is deactivated. The system can vary the effective compression ratio between higher for cold starting and other selected operating conditions and lower for warmed-up running, as well as trap additional exhaust residuals to assist starting and light load. This is especially useful for Diesel engines. Various means may be used to unlock the pins including oil pressure, bi-metal spring temperature, or electromagnetic activation. The telescoping motion which limits the motion of the valve may occur in one or more steps.