The Piston Cup
The position of the piston that has not reached TDC
BTDC
An engine that relies on electrical spark to ignite air/fuel mixture
SI or spark ignition
The stroke in the engine cycle when the piston moves from TDC to BDC
Intake stroke or power stroke
A shaft with lobes that operate the valve mechanisms
Camshaft
The clearance between the piston and cylinder wall
Piston clearance
The metal between the ring grooves, that supports the rings
Ring lands
An engine that runs on heat applied externally to the cylinder, i.e. steam engine
External Combustion Engine
An up and down motion with the cylinder
Reciprocating motion
An engine that has enough clearance between piston and valves that they do not hit if timing belt brakes
Freewheeling
An engine that burns fuel internally and creates movement due to thermal gas expansion
Internal combustion engine
The reinforced area of the piston, where the wrist pin attaches to the piston
Piston Pin Boss
The effort to produce a push or pull action
Force
The stroke when the piston moves up and burned gasses are pushed out of cylinder
Exhaust
The amount the valve will open
Lift
The position of the piston once it has moved beyond top dead center
ATDC
The volume of air that is moved by the piston
Displacement
Locking devices that keep the valve retained by the valve spring seat
Keepers
The lighting of the air fuel mixture in the combustion chamber
The time during which the intake and exhaust valves are open at the same time
overlap
The amount of time the valve stays open given in degrees of rotation of the crankshaft
Duration
The area below the ring groove that prevents piston from cocking or jamming in bore
Piston Skirt
The result of combustion gasses leaking past rings and getting into crankcase
Blow-by gas
The stroke of the piston which air fuel mixture is pushed into a small area
Compression
An engine in which the camshaft is located in the engine block
Cam-in-block or overhead valve
A device that is able to shift camshaft timing while the camshaft is turning
Phaser