Dictionary of Automotive Terms: B

BACKFIRE (Intake system): Burning of fuel mixture in intake manifold. May be caused by faulty timing, crossed plug wires, leaky intake valve, etc.

BACKFIRE (Exhaust system): Passage of unburned fuel mixture into exhaust system where it's ignited and causes an explosion (backfire).

BACKLASH: Amount of “play” between two parts. In case of gears, it refers to how much one gear can be moved back and forth without moving gear into which it's meshed.

BACK PRESSURE: Refers to resistance to flow of exhaust gases through exhaust system.

BACKUP LIGHTS: White lights attached to the rear of a vehicle. Lights are turned on whenever transmission is placed in reverse. Provides illumination for backing at night.

BAFFLE: Obstruction used to slow down or divert the flow of gases, liquids, sound, etc.

BALANCE (Tire): See Static Balance and Dynamic Balance.

BALK RING: Ring attached to balk gear hub in overdrive unit. It lets gear rotate while ring is stationary.

BALL AND TRUNION: Type of universal joint using needle bearing mounted balls which swivel inside sockets.

BALL BEARING: (Antifriction): Bearing consisting of an inner and outer hardened steel race separated by a series of hardened steel balls.

BALL JOINT: Flexible joint utilizing ball and socket type of construction. Used in steering linkage setups, steering knuckle pivot supports, etc.

BALL JOINT ROCKER ARMS: Rocker arms that instead of being mounted on shaft, are mounted upon ball-shaped device on end of stud.

BALL JOINT STEERING KNUCKLE: Steering knuckle that pivots on ball joints instead of on a kingpin.

BALLAST RESISTOR: Resistor constructed of special type wire, properties of which tend to increase or decrease voltage in direct proportion to heat of wire.

BAROMETRIC PRESSURE: Atmospheric pressure as determined by a barometer.

BASE CIRCLE: As applied to camshaft— lowest spot on cam. Area of cam directly opposite lobe.

BATTERY: Electrochemical device for producing electricity.

BATTERY CAPACITY: Rating of current output of battery. Determined by plate size, number of plates, and amount of acid in electrolyte.

BATTERY CHARGING: Process of renewing battery by passing electric current through battery in reverse direction.

BATTERY — MAINTENANCE-FREE: A battery so designed as to not need any additional water during its normal service life.

BATTERY RATING: Standardized measurement of battery’s ability to deliver electrical energy under specified conditions.

BATTERY RESERVE CAPACITY: Measurement (in minutes) of battery’s ability to supply electrical energy to the electrical system in event generating system is in operative.

BATTERY RESERVE CAPACITY

RATING: The measure of number of minutes a full charged battery at 80°F (26.7°C) can be discharged at 25 amperes and still maintain a minimum voltage of 1.75 volts per cell.

BATTERY SHEDDING: Grids loosing active materials that fall off and settle in bottom of battery case.

BATTERY STATE OF CHARGE: Electrical energy available from a given battery in relation to that which would be normally available if battery were fully charged.

BATTERY VOLTAGE: Determined by the number of cells. Each cell has 2.1V. Three cells will produce a 6V battery and six cells a 12V battery.

BBDC: Before Bottom Dead Center.

BCI: Battery Council International.

BDC: Bottom Dead Center.

BEAD (Tire): Steel wire reinforced portion of tire that engages the wheel rim.

BEARING: Area of unit in which contacting surface of a revolving part rests.

BEARING CLEARANCE: Amount of space left between shaft and bearing surface. This space is for lubricating oil to enter.

BELL HOUSING (Clutch housing): Metal covering around flywheel and clutch, or torque converter assembly.

BELTED BIAS: Tire plies crisscrossed; belts beneath tread area.

BENDIX TYPE STARTER DRIVE: A self- engaging starter drive gear. Gear moves into engagement when starter starts spinning and automatically disengages when starter stops.

BEVEL GEAR: Gear in which teeth are cut in a cone shape, as found in axle end gears.

BEVEL SPUR GEAR: Gear in which teeth are cut in a cone shape. Teeth are aligned with cone centerline, as found in some differential gears.

BEZEL: Crimped edge of metal that secures glass face to an instrument.

BHP: Brake horsepower. Measurement of actual power produced by engine.

BIAS PLY: Tire plies crisscross; belts not used under tread area.

BLEEDING: Removing air, pressure, fluid, etc., from a closed system, as in air conditioning.

BLEEDING THE BRAKES: Refers to removal of air from hydraulic system. Bleeder screws are loosened at each wheel cylinder, (one at a time) and brake fluid is forced from master cylinder through lines until all air is expelled.

BLOCK: Part of engine containing cylinders.

BLOW-BY: Refers to escape of exhaust gases past piston rings.

BLOWER: Supercharger.

BLUEPRINTING (Engine): Dismantling engine and reassembling it to EXACT specifications.

BMEP: Brake Mean Effective Pressure.

BODY PUTTY: Material designed to smooth on dented body areas. Upon hardening, putty is dressed down and area painted.

BOILING POINT: Exact temperature at which a liquid begins to boil.

BONDED BRAKE LINING: Brake lining that's attached to brake shoe by adhesive.

BOOSTER. Device incorporated in car system (such as brakes and steering), to in crease pressure output or decrease amount of effort required to operate or both.

BOOT: British term for trunk.

BORE: May refer to cylinder itself or to diameter of the cylinder.

BORE DIAMETER: Diameter of cylinders.

BORING: Renewing cylinders by cutting them out to a specified size. Boring bar is used to make cut.

BORING BAR (Cylinder): Machine used to cut engine cylinders to specific size. As used in garages, to cut worn cylinders to a new diameter.

BOSS: A rib or enlarged area designed to strengthen a certain portion or area of an object.

BOTTLED GAS: LPG (Liquefied Petroleum Gas) gas compressed into strong metal tanks. When confined in tank under pressure, gas is in liquid form.

BOUND ELECTRONS: Electrons in inner orbits around nucleus of atom. They are difficult to move out of orbit.

BOURDON TUBE: Circular, hollow piece of metal used in some instruments. Pressure on hollow section causes it to attempt to straighten. Free end then moves needle on gauge face.

BOXED FRAME: A frame in which two channel shaped rails are welded together (open side to open side) forming a box shape providing great strength.

BOXED ROD: Connecting rod in which I-beam section has been stiffened by welding plates on each side of the rod.

BRAKE ANCHOR: Steel stud upon which one end of brake shoes is either attached to or rests against. Anchor is firmly affixed to backing plate.

BRAKE ANTI-ROLL DEVICE: Unit in stalled in brake system to hold brake line pressure when car is stopped on upgrade. When car is stopped on upgrade and brake pedal released, anti-roll device will keep brakes applied until either clutch is released or, as on some models, accelerator is de pressed.

BRAKE BACKING PLATE: Rigid steel plate upon which brake shoes are attached. Braking force applied to shoes is absorbed by backing plate.

BRAKE BAND: Band, faced with brake lining, that encircles a brake drum. Used on several parking brake installations.

BRAKE BLEEDING: See Bleeding the Brakes.

BRAKE CYLINDER: See Wheel Cylinder.

BRAKE — DISC TYPE: Braking system that instead of using conventional brake drum with internal brake shoes, uses steel disc with caliper type lining application. When brakes are applied, section of lining on each side of spinning disc is forced against disc thus imparting braking force. This type of brake is very resistant to brake fade.

BRAKE DRUM: Cast iron or aluminum housing, bolted to wheel, that rotates around brake shoes. When shoes are expanded, they rub against machined inner surface of brake drum and exert braking effect upon wheel.

BRAKE DRUM LATHE: Machine to refinish inside of a brake drum.

BRAKE FADE: Reduction in braking force due to loss of friction between brake shoes and drum. Caused by heat buildup.

BRAKE FEEL: Discernible, to driver, relationship between the amount of brake pedal pressure and the actual braking force being exerted. Special device is incorporated in power brake installations to give driver this feel.

BRAKE FLUID: Special fluid used in hydraulic brake systems. Never use anything else in place of regular fluid.

BRAKE FLUSHING: Cleaning brake system by flushing with alcohol or brake fluid. Done to remove water, dirt, or any other contaminant. Flushing fluid is placed in master cylinder and forced through lines and wheel cylinders where it exits at cylinder bleed screws.

BRAKE HORSEPOWER (bhp): Measurement of actual usable horsepower delivered at crankshaft. Commonly computed using an engine on a chassis dynamometer.

BRAKE HOSE: Flexible hose which connects brake lines to wheel cylinders. It allows suspension movement without damage.

BRAKE LINE: Steel tubing which carries brake fluid from master cylinder to wheel cylinders.

BRAKE LINING: Friction material fastened to brake shoes. Brake lining is pressed against rotating brake drum thus stopping car.

BRAKE — PARKING or EMERGENCY: Brake used to hold car in position while parked. One type applies rear brake shoes by mechanical means and other type applies brake band to brake drum installed in drive train.

BRAKE — POWER: Conventional hydraulic brake system that utilizes either engine vacuum or hydraulic pressure to operate a power piston. Power piston applies pressure directly to master cylinder piston. This reduces amount of pedal pressure driver must exert to stop car.

BRAKE SHOE GRINDER: Grinder used to grind brake shoe lining so it will be square to and concentric with brake drum.

BRAKE SHOE HEEL: End of brake shoe adjacent to anchor bolt or pin.

BRAKE SHOE TOE: Free end of shoe, not attached to or resting against an anchor pin.

BRAKE SHOES: Part of brake system, located at wheels, upon which brake lining is attached. When wheel cylinders are actuated by hydraulic pressure, they force brake shoes apart and bring lining into contact with drum.

BRAKES — POWER BOOSTER (Hydraulic): Brake booster employing hydraulic pressure from the power steering system to apply force to master cylinder.

BRAZE: To join two pieces of metal together by heating edges to be joined and then melting drops of brass or bronze on area. Unlike welding, this operation is similar to soldering, only a higher melting point material is used.

BREAK-IN: Period of operation between installation of new or rebuilt parts and time in which parts are worn to the correct fit. Driving at reduced and varying speed for a specified mileage to permit parts to wear to the correct fit.

BREAK-OVER ANGLE: Included angle that a vehicle can cross over without dragging underneath center section. Break-over angle is determined by vehicle ground clearance and wheelbase.

BREAKER (Tire): Rubber or fabric (or both) strip placed under tread to provide additional protection for main tire carcass.

BREAKER ARM: Movable arm upon which one of breaker points is affixed.

BREAKER POINTS (Ignition): Pair of movable points that are opened and closed to break and make the primary circuit.

BREATHER PIPE: Pipe opening into interior of engine. Used to assist ventilation. Pipe usually extends downward to a point just below engine so passing air stream will form a partial vacuum thus assisting in venting engine.

BROACH: Bringing metal surface to desired shape by forcing multiple-edged cutting tool across surface.

BRONZE: An alloy basically consisting of tin and copper.

BRUSH: Pieces of carbon, or copper, that rub against the commutator on the generator and starter motor.

B&S GAUGE (Brown and Sharpe): Standard measure of wire diameter.

BTDC: Before Top Dead Center.

BTU (British thermal unit): Measurement of the amount of heat required to raise temperature of one pound of water, one degree Fahrenheit.

BUDC: Before Upper Dead Center. Same as BTDC.

BURNISH: To bring a surface to a high shine by rubbing with hard, smooth object.

BUSHING: Bearing for shaft, spring shackle, piston pin, etc., of one piece construction which may be removed from part.

BUTANE: Petroleum gas that's liquid, when under pressure. Often used as engine fuel in trucks.

BUTTERFLY VALVE: Valve in carburetor that's so named due to its resemblance to in sect of same name.

BYPASS: To move around or detour regular route or circuit taken by air, fluid, electricity, etc.

BY-PASS FILTER: Oil filter that constantly filters’ PORTION of oil flowing through engine.

BY-PASS VALVE: Valve that can open and allow fluid to pass through in other than its normal channel.