Dictionary of Automotive Terms: S

SAE: Society of Automotive Engineers.

SAE or RATED HORSEPOWER: A simple formula of long standing is used to deter mine what is commonly referred to as the SAE or Rated Horsepower. The formula is: (Bore Diameter x Number of Cylinders / 2.5). This formula is used primarily for licensing purposes and is not too accurate a means of determining actual brake horsepower.

SAFETY FACTOR: Providing strength beyond that needed, as an extra margin of insurance against part failure.

SAFETY HUBS: Device installed on the rear axle to prevent wheels from leaving car in event of a broken axle.

SAFETY RIM: Rim having two safety ridges, one on each lip, to prevent tire beads from entering drop center area in event of a blowout. This feature keeps tire on rim.

SAFETY VALVE: Valve designed to open and relieve pressure within a container when container pressure exceeds predetermined level.

SAND BLAST: Cleaning by the use of sand propelled at high speeds in an air blast.

SAYBOLT VISCOMETER: Instrument used to determine fluidity or viscosity (resistance to flow) of an oil.

SCALE (Cooling System): Accumulation of rust and minerals within cooling system.

SCATTER SHIELD: Steel or nylon guard placed around bell or clutch housing to protect driver and spectator from flying parts in event of part failure at high rpm. Such a shield is often placed around transmissions and differential units.

SCAVENGING: Referring to a cleaning or blowing out action in reference to the exhaust gas.

SCHRADER VALVE: Valve, similar to spring loaded valve used in tire stem, used in car air conditioning system service valves.

SCORE: Scratch or groove on finished surface.

SCREW EXTRACTOR: Device used to remove broken bolts, screws, etc., from holes.

SCS: Speed Control Switch. (Speed sensitive spark advance control.)

SEAL: Device which prevents oil leakage around moving part.

SEALED BEAM HEADLIGHT: Headlight lamp in which lens, reflector, and filament are fused together to form single unit.

SEALED BEARING: Bearing that has been lubricated at factory and then sealed. It can not be lubricated during service.

SEAT: Surface upon which another part rests or seats. Example: Valve seat is matched surface upon which valve face rests.

SEAT (Rings): Minor wearing of piston ring surface during initial use. Rings then fit or seat properly against the cylinder wall.

SECONDARY CIRCUIT (Ignition System): High voltage part of ignition system.

SECONDARY, REVERSE, or TRAILING BRAKE SHOE: Brake shoe that's installed facing rear of car.

SECONDARY WIRES: High voltage wire from coil to distributor central tower and from outer towers to spark plugs.

SECTION MODULUS: Relative structural strength measurement of member (such as frame rail) that's determined by cross- sectional area and member shape.

SECTION WIDTH (Tire): Overall width minus height of any lettering or pattern extending outward from sidewalls.

SEDIMENT: Accumulation of matter which settles to bottom of a liquid.

SEIZE: See Freezing.

SELF-ENERGIZING: Brake shoe (some times both shoes) that when applied develops wedging action that actually assists or boosts braking force applied by wheel cylinder.

SELF-INDUCTION (Electromagnetic): Creation of voltage in a circuit by varying cur rent in circuit.

SEMA: Specialty Equipment Manufacturer’s Association.

SEMI-ELLIPTICAL SPRING: Spring, such as commonly used on truck rear axles, consisting of one main leaf and number of progressively shorter leaf springs.

SEMI-FLOATING AXLE: Type of axle commonly used in modern car. Outer end turns wheel and supports weight of car; inner end which is splined, “floats” in differential gear.

SEPARATORS ( Battery): Wood, rubber, or plastic sheets inserted between positive and negative plates to prevent contact.

SERIES CIRCUIT: Circuit with two or more resistance units so wired that current must pass through one unit before reaching other.

SERIES-PARALLEL CIRCUIT: Circuit of three or more resistance units in which a series and a parallel circuit are combined.

SERVICEABLE: A part or unit whose design and construction permit disassembly for purposes of rebuilding. Can also be used to indicate a part or unit whose condition is such that it can still be used.

SERVICE MANAGER: Person in charge of overall shop or garage operation.

SERVICE VALVES: Valves in air conditioning system which allow system to be charged (filled), evacuated (emptied), and tested with pressure gauges.

SERVO (Transmission): Oil operated device used to push or pull another part -- such as tightening the transmission brake bands.

SERVO ACTION: Brakes so constructed as to have one end of primary shoe bearing against end of secondary shoe. When brakes are applied, primary shoe attempts to move in the direction of the rotating drum and in so doing applies force to the secondary shoe. This action, called servo action, makes less brake pedal pressure necessary and is widely used in brake construction.

SHACKLE: Device used to attach ends of a leaf spring to frame.

SHAVE: Removal of some chrome or decorative part.

SHAVE (Engine): Removal of metal from contact surface of cylinder head or block.

SHIFT FORKS: Devices that straddle slots cut in sliding gears. Fork is used to move gear back and forth on shaft.

SHIFT MECHANISM: Device for changing transmission gears range.

SHIFT POINT: Point, either in engine rpm or road speed, at which transmission should be shifted to next gear.

SHIFT RAILS: Sliding rods upon which shift forks are attached. Used for shifting the transmission (manual).

SHIFT RANGE (4-wheel drive): Used to refer to two-speed transfer case gear position. Case can be shifted into HIGH RANGE (no gear reduction) or LOW RANGE (around two to one reduction).

SHIM: A thin piece of brass, steel, etc., inserted between two parts so as to adjust distance between them. Sometimes used to adjust bearing clearance.

SHIMMY: Front wheels shaking from side to side.

SHOCK ABSORBER: Oil filled device used to control spring oscillation in suspension system.

SHORT BLOCK: Engine block complete with crankshaft and piston assemblies.

SHROUD: Metal enclosure around fan, engine, etc., to guide and facilitate flow of air.

SHORT or SHORT CIRCUIT: Refers to some “hot” portion of the electrical system that has become grounded. (Wire touching a ground and providing a completed circuit to the battery.)

SHRINK-FIT: Fit between two parts which is so tight, outer or encircling piece must be expanded by heating so it will fit over inner piece. In cooling, outer part shrinks and grasps inner part securely.

SHUNT: An alternate or by-pass portion of an electrical circuit.

SHUNT WINDING: Wire coil forming an alternate or bypass circuit through which current may flow.

SIDE-DRAFT CARBURETOR: Carburetor in which air passes though carburetor into intake manifold in a horizontal plane.

SIDEWALL: Part of tire between tread and bead, usually has size and rating information.

SIGHT GLASS: Clear glass window in air conditioning line which lets mechanic check refrigerant for air bubbles (low refrigerant) and moisture (pink color).

SILENCER: Muffler.

SILVER SOLDER: Similar to brazing except that special silver solder metal is used.

SINGLE-BARREL, DOUBLE-BARREL, and FOUR-BARREL CARBURETORS: Number of throttle openings or barrels from the carburetor to the intake manifold.

SINTERED BRONZE: Tiny particles of bronze pressed tightly together so that they form a solid piece. The piece is highly porous and is often used for filtering purposes.

SIPE: Small slits in tire tread designed to in crease traction. Also called kerfs.

SKID PLATE: Stout metal plate or plates attached to underside of vehicle to protect oil pan, transmission, fuel tank, etc., from damage caused by “grounding out” on rocks, curbs, and road surface.

SKIVING: Cutting away a portion of tire tread to correct out-of-round problem.

SLANT ENGINE: In-line engine in which cylinder block has been tilted from vertical plane.

SLEEVE (Cylinder): See Cylinder Sleeve.

SLIDING-FIT: See Running-Fit.

SLIDING GEAR: Transmission gear splined to, the shaft. It may be moved back and forth for shifting purposes.

SLIP ANGLE: Difference in actual path taken by a car making a turn and path it would have taken if it had followed exactly as wheels were pointed.

SLIP JOINT: Joint that will transfer driving torque from one shaft to another while allowing longitudinal movement between two shafts.

SLINGSHOT: Form of dragster using rather long thin frame with a very light front axle and wheel assembly.

SLUDGE: Black, mushy deposits throughout interior of the engine. Caused from mixture of dust, oil, and water being whipped together by moving parts.

SMOG: Fog made darker and heavier by chemical fumes and smoke.

SNAP RING: Split ring snapped into a groove in a shaft or in a groove in a hole. It is used to hold bearings, thrust washers, gears, etc., in place.

SNUBBER: Device used to limit travel of some part.

SODIUM VALVE: Valve in which stem has been partially filled with metallic sodium to speed up transfer of heat from valve head, to stem and then to guide and block.

SOHC: Engine with single overhead cam shaft.

SOLDERING: Joining two pieces of metal together with lead-tin mixture. Both pieces of metal must be heated to insure proper adhesion of melted solder.

SOLENOID: Electrically operated magnetic device used to operate some unit. Movable iron core is placed inside of coil. When cur rent flows through coil, core will attempt to center itself in coil. In so doing, core will exert considerable force on anything it's connected to.

SOLID AXLE: Single beam runs between both wheels. May be used on either front or rear of car.

SOLID STATE: An electrical device, such as a regulator, that has no moving parts. Such units use transistors, diodes, resistors, etc., to perform all electrical functions.

SOLVENT: Liquid used to dissolve or thin other material. Examples: Alcohol thins shellac; gasoline dissolves grease.

SPARK: Bridging or jumping of a gap between two electrodes by current of electricity.

SPARK ADVANCE: Causing spark plug to fire earlier by altering position of distributor breaker points in relation to distributor shaft.

SPARK ARRESTOR: Device used to prevent sparks (burning particles of carbon) from being discharged from exhaust pipe. Usually used on off-road equipment to prevent forest fires.

SPARK GAP: Space between center and side electrode tips on a spark plug.

SPARK KNOCK: See Pre-ignition.

SPARK PLUG: Device containing two electrodes across which electricity jumps to pro duce a spark to fire fuel charge.

SPECIALIZATION: When a mechanic concentrates in one particular area of auto repair — brakes, tune-up, transmission, engines.

SPECIFIC GRAVITY: Relative weight of a given volume of specific material as com pared to weight of an equal volume of water.

SPEED: Time rate of motion without regard to direction. Forward speed (mph or km/h) of a vehicle, rotational speed (rpm) of an engine, etc.

SPEEDOMETER: Instrument used to deter mine forward speed of an auto in miles per hour or kilometers per hour.

SPIDER GEARS: Small gears mounted on shaft pinned to differential case. They mesh with, and drive, the axle end gears.

SPINDLE (Wheel): Machined shaft upon which inside races of front wheel bearings rest. Spindle is an integral part of steering knuckle.

SPIRAL BEVEL GEAR: Ring and pinion setup widely used in automobile differentials. Teeth of both ring and pinion are tapered and are cut on a spiral so that they are at an angle to center line of pinion shaft.

SPLINE: Metal (land) remaining between two grooves. Used to connect parts.

SPLINED JOINT: Joint between two parts in which each part has a series of splines cut along contact area. The splines on each part slide into grooves between splines on other part.

SPLIT MANIFOLD: Exhaust manifold that has a baffle placed near its center. An exhaust pipe leads out of each half.

SPONGY PEDAL: When there is air in brake lines, or shoes that are not properly centered in drums, brake pedal will have a springy or spongy feeling when brakes are applied. Pedal normally will feel hard when applied.

SPOOL BALANCE VALVE (Automatic Transmission): Hydraulic valve that balances incoming oil pressure against spring control pressure to produce a steady pressure to some control unit.

SPOOL VALVE: Hydraulic control valve shaped somewhat like spool upon which thread is wound.

SPORTS CAR: Term commonly used to describe a relatively small, low slung, car with a high performance engine.

SPOT WELD: Fastening parts together by fusing, at various spots. Heavy surge of electricity is passed through the parts held in firm contact by electrodes.

SPRAG CLUTCH: Clutch that will allow rotation in one direction but that will lock up and prevent any movement in the other direction.

SPRING (Main Leaf): Long leaf on which ends are turned to form an “eye” to receive shackle.

SPRING BOOSTER: Device used to “beef” up sagged springs or to increase the load capacity of standard springs.

SPRING CAPACITY AT GROUND: Total vehicle weight (sprung and un-sprung) that will be carried by spring bent or deflected to its maximum normal loaded position.

SPRING CAPACITY AT PAD: Total vehicle sprung weight that will be carried by spring bent or deflected to its normal fully loaded position.

SPRING LOADED: Device held in place, or under pressure from a spring or springs.

SPRING STEEL: Heat treated steel having the ability to stand a great amount of deflection and yet return to its original shape or position.

SPRING WINDUP: Curved shape assumed by rear leaf springs during acceleration or braking.

SPROCKET: Toothed wheel used to drive chain or cogged belt.

SPRUNG WEIGHT: Weight of all parts of car that are supported by suspension system.

SPUR GEAR: Gear on which teeth are cut parallel to shaft.

SPURT or SQUIRT HOLE: Small hole in connecting rod big end that indexes (aligns) with oil hole in crank journal. When holes index, oil spurts out to lubricate cylinder walls.

SQUARE ENGINE: Engine in which bore diameter and stroke are of equal dimensions.

SQ. FT.: Square Foot.

SQ. IN.: Square Inch.

STABILIZER BAR: Transverse mounted spring steel bar that controls and minimizes body lean or tipping on corners.

STALL: To stop rotation or operation.

STAMPING: Sheet metal part formed by pressing between metal dies.

STARTER (Engine): Electric motor which uses a gear-drive to crank (spin) engine for starting.

STARTER PINION GEAR: Small gear on end of starter shaft that engages and turns large flywheel ring gear.

STARTER SOLENOID: Large electric relay that makes and breaks the electrical connection between the battery and starting motor.

STARTING SYSTEM: Parts (starter motor, gear drive, switch, solenoid, wires, battery, etc.) involved in system used to crank car for starting.

STATIC BALANCE: When a tire, flywheel, crankshaft, etc., has an absolutely even distribution of weight mass around axis of rotation, it will be in static balance. For ex ample, if front wheel is jacked up and tire, regardless of where it's placed, always slowly turns and stops with the same spot down, it would not be in static balance. If, how ever, wheel remains in any position in which it's placed, it would be in static balance. (Bearings must be free, no brake drag, etc.)

STATIC ELECTRICITY: Electricity generated by friction between two objects. It will remain in one object until discharged.

STATIC PRESSURE (Brakes): Certain amount of pressure that always exists in brake lines — even with brake pedal released. Static pressure is maintained by a check valve.

STATIC RADIUS: Distance from road surface to center of wheel with vehicle normally loaded, at rest.

STATIC SUPPRESSION: Removal or minimizing of unwanted electromagnetic waves that cause radio static interference (hissing, crackling, etc.).

STATOR: Small hub, upon which series of vanes are affixed in radial position, that's so placed that oil leaving torque converter turbine strikes stator vanes and is redirected into pump at an angle conducive to high efficiency. Stator makes torque multiplication possible. Torque multiplication is highest at stall when the engine speed is at its highest and the turbine is standing still.

STEEL PACK MUFFLER: Straight-through (no baffled) muffler utilizing metal shavings surrounding a perforated pipe. Quiets exhaust sound.

STEERING ARMS: Arms, either bolted to, or forged as an integral part of steering knuckles. They transmit steering force from tie rods to knuckles, thus causing wheels to pivot.

STEERING AXIS INCLINATION: See Kingpin Inclination.

STEERING GEAR: Gears, mounted on lower end of steering column, used to multi ply driver turning force.

STEERING GEOMETRY: Term sometimes used to describe various angles assumed by components making up front wheel turning arrangement, camber, caster, toe-in, etc. Also used to describe related angles assumed by front wheels when car is negotiating a curve.

STEERING KNUCKLE: Inner portion of spindle affixed to and pivoting on either a kingpin or on upper and lower ball joints.

STEERING KNUCKLE ANGLE: Angle formed between steering axis and centerline of spindle. This angle is sometimes referred to as Included Angle.

STEERING LINKAGE: Various arms, rods, etc., connecting steering gear to front wheels.

STEERING SYSTEM: All parts (steering wheel, shaft, gears, linkage, etc.) used in transferring motion of steering wheel to front wheels.

STETHOSCOPE: Device (such as used by doctors) to detect and locate abnormal engine noises. Very handy tool for trouble shooter.

STICK SHIFT: Transmission that's shifted manually through use of various forms of linkage. Often refers to upright gearshift stick that protrudes through floor.

Either floor or steering column mounted manual shift device for transmission.

STOCK CAR: Car as built by factory.

STOICHIOMETRIC FUEL MIXTURE: A fuel mixture in which proportions of air and fuel are such as to permit complete burning. The ideal mixture for any given engine and set of conditions.

STOPLIGHT: Warning lights, red in color, attached to rear of vehicle. Stoplights come on whenever brake pedal is depressed.

STORAGE BATTERY: Another term for car battery. See Battery.

STOVEBOLT: Generally refers to Chevrolet (GMC) 6-cylinder, in-line, valve-in-head (push rod operated) engine.

STREET ROD: Slightly modified rod that will give good day-to-day performance on the streets.

STRESS: To apply force to an object. Force or pressure an object is subjected to.

STRIPING TOOL: Tool used to apply paint in long narrow lines.

STROBOSCOPE: See Timing Light.

STROKE: Distance piston moves when traveling from TDC to BDC.

STROKED CRANKSHAFT: Crankshaft, either special new one or stock crank re worked, that has connecting rod throws off set so that length of stroke is increased.

STROKER: Engine using crankshaft that has been stroked.

STUD: Metal rod with threads on both ends.

STUD PULLER: Tool used to install or remove studs.

SUCTION: See Vacuum.

SUCTION LINE: See Low Pressure Line.

SUCTION THROTTLING VALVE: Valve placed between air conditioning evaporator and compressor which controls evaporator pressure to provide maximum cooling without icing evaporator core.

SULFATION: Formation of lead sulphate on battery plates.

SUMP: Part of oil pan that contains oil.

SUN GEAR: Center gear around which planet gears revolve.

SUPER CAR: Car with high horsepower engine that will provide fast acceleration and high speed.

SUPERCHARGER: Unit designed to force air, under pressure, into cylinders. Can be mounted between carburetor and cylinders or between carburetor and atmosphere.

SUPERHEAT SWITCH: See Compressor Protection Switch.

SURE-GRIP DIFFERENTIAL: High traction differential which causes both axles to rotate under power.

SWAY BAR: See Stabilizer Bar.

SWEATING: Joining two pieces of metal together by placing solder between them and then clamping them tightly together while heat, sufficient to melt the solder, is applied.

SWING AXLE: Independent rear suspension system in which each driving wheel can move up or down independently of other. Differential unit is bolted to frame and various forms of linkage are used upon which to mount wheels. Drive axles, utilizing one or more universal joints, connect differential to drive wheels.

SWITCH (Electric): A device to make (complete) or break (interrupt) flow of current through a circuit.

SYNCHROMESH TRANSMISSION: Trans mission using device (synchromesh) that synchronizes speeds of gears that are being shifted together. This prevents “gear grinding.” Some transmissions use synchromesh on all shifts, while others synchronize second and high gearshifts.

SYNCHRONIZE: To bring about a timing that will cause two or more events to occur simultaneously; plug firing when the piston is in correct position, speed of two shafts being the same, valve opening when piston is in correct position, etc.