RECIPROCATING Moving back and forth; as a
piston reciprocating in a cylinder.
RELIEF VALVEA valve that opens when a preset
pressure is reached.
This relieves or prevents
REVOLUTION A term to describe a 360° circular
motion of the crankshaft.
RICH MIXTUREAn air-fuel mixture that has a low
proportion of air and a high proportion of fuel.
ROCKER ARMA device that rocks or pivots on the
rocker arm shaft as the cam rotates, causing the
valve to open.
ROCK POSITIONThe piston and connecting rod
position (top or bottom dead center) at which the
crank can rock or rotate a few degrees without
appreciable movement of the piston.
ROD CAPThe lower part of a connecting rod that
can be taken off by removing bolts or nuts so the rod
can be detached from the crankshaft.
SAESociety of Automotive Engineers.
SCAVENGING-A cleaning or blowing out action in
reference to exhaust gases.
SEMIFLOATING PISTON PINA piston pin in
which the ends of the pin are free to move in the
piston bearings of the bosses.
SHROUDA hood placed around an engine fan to
improve air flow.
SLEEVE METERINGA system of metering fuel
delivery by incorporating a movable sleeve with
which port opening and/or port closing is
SMOGA term coined from the words "smoke" and
"fog." First applied to the foglike layer that hangs in
the air under certain atmospheric conditions;
generally used to describe any condition of dirty air
and/or fumes or smoke.
SOHCSingle overhead camshaft.
SPILL VALVEA valve used to end injection at a
controllable point on the pumping stroke by
allowing fuel to escape from the pumping chamber.
SPRING RETAINERThe piece of metal that holds
the valve spring in place, and is itself locked in
place by the valve spring retainer locks.
STATIONARY PARTSThe main parts of an engine
that do not move, but provide support
STROKEThe movement, or the distance of the
movement, in either direction, of the piston travel in
SUPERCHARGERIn the intake system of the
engine, a pump that pressurizes the incoming air or
air-fuel mixture. This increases the amount of fuel
that can be burned, increasing engine power. If the
supercharger is driven by the engine exhaust gas, it
is called a turbocharger.
SUPPLY PUMPA pump for transferring the fuel
from the tank and delivering it to the injection
TANK SENDING UNITA device in the fuel tank
that provides indication of fuel level for instrument
TDC (TOP DEAD CENTER)The position of a
reciprocating piston at its uppermost point of
TEMPERATURE INDICATORA gauge that
indicates to the operator the temperature of the
engine coolant, or a light that comes on if the
coolant gets too hot.
THERMAL EFFICIENCYThe ratio between the
power output and the energy in the fuel burned to
produce the output.
THERMOSTATA device for automatic regulation
of temperature; usually contains a temperature-
sensitive element that expands or contracts to
open and close off the flow of air, a gas, or a
THERMOSTATIC SWITCHA switch that is
turned on or off by temperature change.
THRUSTA force tending to push a body out of
alignment, A force exerted endwise through a
member upon another member.
THRUST BEARINGBearing that limits the axial
(longitudinal) movement of the shaft.
TIMING DEVICEA device responsive to engine
speed and/or load to control the timed relationship
between injection cycle and engine cycle.
TORQUEA force that produces a turning or twisting
effort; measured in pound-feet.