Dictionary of Automotive Terms: N-O

- N -

NADA: National Automobile Dealers’ Association.

NASCAR: Letters denoting National Association for Stock Car Auto Racing.

NBFU: National Board of Fire Underwriters.

NC THREADS: National Coarse thread sizes.

NEEDLE BEARING (Antifriction): Roller type bearing in which rollers have very narrow diameter in relation to their length.

NEEDLE VALVE: Valve with long, thin, tapered point that operates in small hole or jet. Hole size is changed by moving needle valve in or out.

NF THREADS: National Fine thread sizes.

NEGATIVE TERMINAL: Terminal (such as on battery) from which current flows on its path to positive terminal.

NEUTRON: Neutral charge particle forming part of an atom.

NEWTON’S LAW: For every action there is an equal, an opposite reaction.

NHRA: National Hot Rod Association.

NHTSA: National Highway Traffic Safety Administration.

NITROGEN OXIDES: In combustion process, nitrogen from air combines with oxygen to form nitrogen oxides.

NLGI: National Lubricating Grease Institute.

NONFERROUS METALS: All metals containing no iron — except in very minute quantities.

NON-SERVICEABLE: A part or device whose design and construction does not permit rebuilding. Can also be used to indicate a part of device that's no longer fit for use.

NORTH POLE (Magnet): Magnetic pole from which lines of force emanate; travel is from north to south pole.

NOx: See Oxides of Nitrogen.

NOZZLE: Opening through which fuel mixture is directed into carburetor air stream.

NSC: National Safety Council.

NUMBER DRILLS: Series of drills in which each size is designated by number (0-80).

- O -

OCTANE RATING: Rating that indicates a specific gasoline’s ability to resist detonation.

OD: Outside diameter.

ODOMETER: Device used to measure and register number of miles traveled by car.

OEM: Original Equipment Manufacturer.

OFF-ROAD VEHICLE: Vehicle designed to operate in rough country (hills, sand, mud, etc.) without benefit of regular roads.

OHM: Unit of measurement used to indicate amount of resistance to flow of electricity in a given circuit.

OHMMETER: Instrument used to measure amount of resistance in given unit or circuit. (In ohms.)

OHM’S LAW: Formula for calculating electrical values in a circuit.

OIL BATH AIR CLEANER: Air cleaner that utilizes a pool of oil to insure removal of impurities from air entering carburetor.

OIL BURNER: Engine that consumes an excessive quantity of oil.

OIL CLASSIFICATION — CA, CB, CC, CD: Classifications for oil designed for use in diesel engines. Many automotive diesel engines require oil marked with classification SF/DC, SF/CC. Follow manufacturers recommendations.

OIL CLASSIFICATION — SA: (Utility Gasoline and Diesel Engine Service.) Oil for applications under light load, moderate speed, highly favorable service. Contains few or no additives.

OIL CLASSIFICATION — SC: (Minimum Duty Gasoline Engine Service.) For mild operating conditions. Contains some additives.

OIL CLASSIFICATION — SC: (1964 Gasoline Engine Service.) For service such as that experienced by engines built from 1964— 1967. Contains additives to retard low temperature deposits, rust, wear, corrosion, etc.

OIL CLASSIFICATION — SD: (1968 Gasoline Engine Warranty Maintenance Service.) For service such as needed for 1968 through 1970 light truck and car engines. Contains more additives than SC oil.

OIL CLASSIFICATION — SE: (1972 Gasoline Engine Warranty Maintenance.) Oil for 1972 through 1979 light truck and car engines. Contains more additives than SD oil.

OIL CLASSIFICATION — SF: (1980 Gasoline Engine Warranty Service.) Oil recommended for 1980 and later car and light truck engines. Provides excellent protection against wear, heat, deposits, etc. Can be used where SE, SD, or SC are recommended.

OIL — COMBINATION SPLASH and PRESSURE SYSTEM: Engine oiling system that uses both pressure and splash oiling to accomplish proper lubrication.

OIL CONTROL RING (Piston): A piston ring designed to prevent excessive oil consumption by scraping excess oil from cylinder and returning it to oil pan sump. Usually lower (furthest down in cylinder) ring or rings.

OIL COOLER: Device used to remove excess heat from engine and/or transmission oil. Can be air or water cooled design.

OIL DIPSTICK: See Dipstick.

OIL FILTER: Device used to strain oil in engine thus removing abrasive particles.

OIL—FULL PRESSURE SYSTEM: Engine oiling system that forces oil, under pressure, to moving parts of engine.

OIL GALLERY: Pipe or drilled passageway in engine used to carry engine oil from one area to another.

OIL GAUGE: A dash-mounted device that indicates engine oil pressure in pounds per square inch (psi) or kilopascals (kPa). Can be of either electrical or Bourdon tube design.

OIL PAN: See Pan.

OIL PICKUP: Connects to oil pump and ex tends into bottom of oil pan. Oil is drawn through pickup into pump.

OIL PUMP: Device used to force oil, under pressure, to various parts of the engine. It is driven by gear on camshaft.

OIL PUMPING: Condition wherein an excessive quantity of oil passes piston rings and is consumed in combustion chamber.

OIL RING: Normally bottom piston ring which scrapes excess oil off cylinder wall.

OIL SEAL: Device used to prevent oil leakage past certain area.

OIL SLINGER: Device attached to revolving shaft so any oil passing that point will be thrown outward where it will return to point of origin.

OIL — SPLASH SYSTEM: Engine oiling system that depends on connecting rods to dip into oil troughs and splash oil to all moving parts.

OIL STRAINER (Engine): A fine wire mesh screen through which oil entering oil pump is drawn. It will remove larger particles of dirt or other abrasives.

OIL SUMP: That portion of oil pan that holds supply of engine oil.

ONE-WAY CLUTCH: It locks shaft in one direction and allows rotation in other direction.

OPEN CIRCUIT: Circuit in which a wire is broken or disconnected.

OPEN CIRCUIT VOLTAGE ( Battery): Cell voltage when battery has no completed circuit across posts and is not receiving or delivering energy.

ORIFICE: A small hole or restricted opening used to control flow of gasoline, air, oil, etc.

OSCILLATING ACTION: Swinging action such as that in pendulum of a clock.

OSCILLOSCOPE: Testing unit which projects visual reproduction of the ignition system spark action onto screen of cathode ray tube.

OTTO CYCLE: Four-stroke cycle consisting of intake, compression, firing, and exhaust strokes.

OUTPUT SHAFT: Shaft delivering power from within mechanism. Shaft leaving transmission, attached to propeller shaft, is transmission output shaft.

OVERDRIVE: Unit utilizing planetary gear set so actuated as to turn drive shaft about one-third faster than transmission output shaft.

OVERDRIVE STAGES: Locked-out; direct, freewheeling; and overdrive.

OVERHEAD CAMSHAFT: Camshaft mounted above the head, driven by long timing chain or belt.

OVERHEAD VALVES: Valves located in head.

OVERRUNNING CLUTCH: Clutch mechanism that will drive in one direction only. If driving torque is removed or reversed, clutch slips.

OVERRUNNING CLUTCH STARTER DRIVE: Starter drive that's mechanically engaged. When engine starts, overrunning clutch operates until drive is mechanically disengaged.

OVERSQUARE ENGINE: Engine in which bore diameter is larger than length of stroke.

OVERSTEER: Tendency for car, when negotiating a corner, to turn more sharply than driver intends.

OXIDES OF NITROGEN (NOx): Undesirable exhaust emission, especially prevalent when combustion chamber flame temperatures are high.

OXIDIZE (Metal): Action where surface of object is combined with oxygen in air to pro duce rust, scale, etc.

OXIDIZING FLAME: Welding torch flame in which an excess of oxygen exists. Free or unburned oxygen tends to burn molten metal.

OXYGEN: Gas, used in welding, made up of colorless, tasteless, odorless, gaseous element oxygen found in atmosphere.