Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Va"

V

A letter rating for tires to indicate that they are theoretically rated for speeds up to 210 kph (130 mph), as in P220VR15. The next higher rating is W and the one lower rating is H.
A letter indicating a valve configuration as in 16v meaning a 16 valve engine.
A letter indicating the configuration of the cylinders in an engine as in V-8
Acronym for Volts

V-4: See
V-four

V-6: See
V-six

V-8: See
V-eight

V-10: See
V-ten

V-12: See
V-twelve

V-16: See
V-sixteen

VA: Value analysis.

Vac: Abbreviation for Vacuum
Also See
Master vac
Master vac servo unit

Vac servo: See
Master vac servo unit

Vac servo unit: See
Master vac servo unit

Vacuum

An enclosed area in which the air pressure is below that of the surrounding Atmospheric pressure.
Technically, a complete absence of pressure (0 psi), although the term is commonly used to describe any pressure less than atmospheric.

Also See
Air-valve carburetor
Constant vacuum
Manifold vacuum
Ported vacuum advance
Pulse vacuum hublock
Venturi vacuum

Vacuum activators: Dampers and control valves used in automotive air conditioning system controlled by the vacuum created by engine intake manifold vacuum.

Vacuum advance: A mechanism on the side of the Distributor that automatically varies the instant at which the Spark occurs as a function of Intake manifold vacuum. Vacuum advance provides the additional advance that is needed when the engine is operating at part throttle. At part throttle less Air-fuel mixture gets into the Cylinders and the mixture takes longer to burn after it is ignited. Because the mixture burns more slowly, the Piston will be past Top dead center and moving down before the mixture has a chance to burn and produce high power. As a result much of the power in the fuel will be lost. The vacuum advance mechanism consists of a flexible spring-loaded Diaphragm connected by a Linkage to the Breaker plate on which the points are mounted. The sealed side of the Diaphragm is connected by a tube to the Carburetor. The Throttle valve is below the vacuum passage in the Carburetor Air horn so there is no vacuum advance when the engine is idling because the throttle is closed. However, when the throttle is partly open, Intake manifold vacuum pulls the Diaphragm in and this causes the Breaker plate to rotate a few degrees and advance the Timing. With wide-open throttle there is very little vacuum in the Intake manifold so there will be no vacuum advance. In most instances the vacuum advance is disconnected before checking the timing and Point gap.

Also See
Ported vacuum advance
Speed control vacuum advance

Vacuum advance mechanism: See
Vacuum advance

Vacuum advance unit: See
Vacuum advance

Vacuum assisted brake: See
Brake booster.

Vacuum assisted brakes: See
Brake booster.

Vacuum assist unit: An actuating mechanism that uses vacuum on one side of a diaphragm as a source of power.

Vacuum booster

A small Diaphragm Vacuum pump, generally in combination with the Fuel pump, that is used to bolster engine Vacuum during Acceleration so that the vacuum operated devices will continue to operate.
A power brake actuating mechanism that uses vacuum on one side of a diaphragm as a power source.

Vacuum brake booster: A device directly connected to the master cylinder and mounted on the engine side of the bulkhead, which uses engine manifold vacuum to produce additional braking force

Vacuum brake supply line: The conduit for transmitting supply vacuum from a vacuum source to the vacuum reservoirs.

Vacuum brake system: A brake system that utilizes vacuum means for operation and control.

Vacuum capsule: A pneumatic actuator that converts air pressure differences into a regulating short-stroke movement; the circular, flat capsule has a spring-loaded diaphragm with a lever attached

Vacuum chamber: A pneumatic actuator that converts air pressure differences into a regulating short-stroke movement; the circular, flat capsule has a spring-loaded diaphragm with a lever attached

Vacuum check valve: (VCK-V) a one-way valve used to retain a vacuum signal in a line after the vacuum source is gone

Vacuum control: A load-dependant mechanical ignition timing, controlled by the inlet manifold vacuum

Vacuum control switch: A switch that monitors the vacuum signal enabling the ECU to recognize open or closed throttle (idle) operation

Vacuum control system: Intake manifold vacuum is used to operate dampers and controls in some automobile systems.

Vacuum control unit: An assembly for load-dependent ignition timing controlled by the intake manifold vacuum, consisting of a vacuum capsule with a spring-loaded diaphragm linked to the breaker plate

Vacuum control valve: (VCV) a ported vacuum switch, controls vacuum to other emission devices during engine warm up

Vacuum delay valve: (VDV) a valve used by GM to bleed ported vacuum to the vacuum advance unit through a small orifice and control vacuum advance rate. Used to retard or delay the application of a vacuum signal. Also called Delay valve

Vacuum differential valve: (VDV) a device used in a Thermactor system with a catalyst that sense intake manifold vacuum and triggers the bypass valve to dump injection air to the atmosphere during deceleration

Vacuum distillation: Distillation under reduced pressure (less the atmospheric) which lowers the boiling temperature of the liquid being distilled. This technique with its relatively low temperatures prevents cracking or decomposition of the charge stock.

Vacuum-electric Switch: Vacuum-electric Switch

A component which gives gross reading of vacuum in the intake manifold by using a diaphragm to operate a simple on-off electrical switch.

Vacuum filter: A filter which removes electrical noise from the vacuum signal sent from the vacuum sensor to the ECU

Vacuum gage: See
Vacuum gauge.

Vacuum gauge: A gauge used to determine the amount of Vacuum existing in a chamber.

Vacuum hose: A pipe which connects the intake manifold to the vacuum brake booster

Vacuum hublock: See
Pulse vacuum hublock

Vacuum hydraulic power unit: A unit consisting of a vacuum brake cylinder or chamber, hydraulic cylinder(s) and control valve, in which driver effort is combined with force from the cylinder piston or chmber diaphragm to displace fluid under pressure for actuation of the brake(s).

Vacuum ignition-timing control: See
Vacuum control

Vacuum leak: A loss of vacuum from a leaking hose or defective gasket

Vacuum modulated EGR: An exhaust gas recirculation in which the amount of exhaust gas admitted to the intake manifold depends on a vacuum signal controlled by throttle position. When the throttle is closed, at idle or during deceleration, there is no vacuum signal to the EGR valve; as the throttle is opened, a vacuum signal is supplied causing the EGR valve to open

Vacuum modulator: A small unit attached to the Automatic transmission. If the vehicle tends to stay in Low gear, shifts with difficulty or produces whitish smoke, has an Automatic transmission, and is constantly low in Transmission fluid, try replacing the vacuum modulator before undertaking major repairs. Most vacuum modulators simply screw into place. See Modulator.

Vacuum motor: A vacuum-actuated device used to operate doors and valves.

Vacuum operated exhaust heat control valve: (VHC) a vacuum operated heat riser valve used by Ford to cause the exhaust to flow through the intake crossover passage for preheating of the air-fuel mixture

Vacuum over hydraulic brake system: A hydraulic-type brake system actuated by a vacuum-powered master cylinder.

Vacuum-powered master cylinder: A brake master cylinder actuated by a vacuum cylinder or chamber.

Vacuum power motor: A device for use in opening doors in heating and air conditioning systems

Vacuum power unit: A device for use in opening valves and doors in heating and air conditioning systems using vacuum as a source of power.

Vacuum pressure: Any pressure less than that exerted by the atmosphere.

Vacuum pump

A Diaphragm type of Pump used to produce a Vacuum.
A special high efficiency device used for creating high vacuums for testing or drying purposes.
A mechanical device used to evacuate an air conditioning system to rid it of moisture, air, and contaminants.
A device which creates a vacuum to actuate the brakes.

Vacuum reducer valve: (VRV) A valve used by GM to limit the amount of vacuum governing the ignition advance mechanism of the distributor; on some ignition systems, a VRV is used to reduce intake manifold vacuum when the coolant temperature is above 104°C, in order to prevent or reduce detonation

Vacuum regulator valve three and four-port: (VRV) this type of vacuum regulator valve is used to control the vacuum advance to the distributor

Vacuum regulator valve two-port: (VRV) this vacuum regulator provides a constant output signal when the input level is greater than a preset level. At a lower input vacuum, the output equals the input

Vacuum relief valve: A valve which automatically opens and closes a vent for relieving a vacuum within the a system, depending on whether the vacuum is above or below a predetermined value.

Vacuum reservoir: (VRESER) stores excess vacuum to prevent rapid fluctuations and sudden drops in a vacuum signal, such as during acceleration

Vacuum restrictor: (VREST) controls the flow rate and/or timing in actions to the different emission control components

Vacuum retard: A vacuum control unit for retarding the spark

Vacuum retard delay valve: (VRDV) delays a decrease in vacuum at the distributor vacuum advance unit when the source vacuum decreases. Used to delay release of vacuum from a diaphragm -- a momentary vacuum trap

Vacuum retard unit: A vacuum control unit for retarding the spark

Vacuum runout point: This refers to the point reached when a vacuum brake power Piston has built up all the braking force it is capable of with the Vacuum available.

Vacuum sealing apparatus: A component in continuous zinc vapor deposition lines through which steel strips enter the deposition chamber and which prevents a build-up of pressure within the chamber

Vacuum sensor: A sensor which detects changes in manifold pressure in comparison to barometric pressure; such changes indicate the need for an adjustment in air/fuel mixture and electronic spark timing to maintain efficient engine operation. Also called Manifold pressure sensor, Pressure differential sensor, or Manifold vacuum sensor

Vacuum servo: A flexible diaphragm with a linkage attached to it installed in a sealed housing. When vacuum is applied to one side of the diaphragm, atmospheric pressure on the other side moves the diaphragm and linkage to perform work.

Also See
Vacuum brake booster

Vacuum solenoid: On some engines, a vacuum solenoid controlled by an electrical sensor switch is used to control the EGR valve

Vacuum suction cup: Dent Puller

A hand tool for pulling out shallow body dents and for lifting flat, heavy objects such as windshields or sheet metal

Vacuum suspended power booster: A type of power booster that contains vacuum in both chambers of the booster when the brake pedal is at rest. When the pedal is applied, the rear chamber is vented to the atmosphere, causing the diaphragm of the booster to move toward the master cylinder which assist the driver in the application of the brakes

Vacuum-suspended power chamber: A booster power chamber that has vacuum on both sides of its diaphragm when the brakes are not applied.

Vacuum switch: A switch that closes or opens its contacts in response to changing vacuum conditions.

Also See
Thermal vacuum switch

Vacuum switching valve: (VSV) an electrically controlled vacuum switching valve used to control emission control devices

Vacuum tank: A tank in which a Vacuum exists. It is generally used to provide vacuum to a Power brake installation in the event engine vacuum cannot be obtained. The tank will supply several brake applications before the vacuum is exhausted.

Vacuum timing control: See
Vacuum control

Vacuum transducer: Vacuum transducer

A sensor with a vacuum diaphragm which moves an iron rod inside a coil of wire sending a signal to the computer that is proportional to the amount of vacuum.

Vacuum transmitting valve: (VTV) a valve used to limit the rate of vacuum advance

Vacuum unit: See
Vacuum control unit

Vacuum valve: See
Thermal vacuum valve

Vacuum vent valve: (VVV) controls the induction of fresh air into a vacuum system to prevent chemical decay of the vacuum diaphragm that can occur on contact with fuel

VAF

Acronym for Vane air-flow meter
Acronym for Volume Air Flow

Valance: A panel used to conceal structural detail or to provide extra protection.

Also See
Rear corner valance
Rear quarter valance
Rear valance

Valet parking: The parking of your car by a parking attendant

Valet switch: On some alarm systems, a switch to override the alarm system for valet parking, car washes, etc.

Value: See
Actual cash value
Cd value
Duty paid value
Expected residual value
Net sales value
Ph value
Residual value
Stated residual value

Value added: See
Census value added

Value of shipment: Summation of value of shipments produced by establishment, receipts of custom and repair revenue.

Valve: A device used to either open or close an opening to allow or prevent the flow of a liquid or gas from one place to another. There are many different types.

Also See
ABS relay valve
Accumultor valve
Air-valve carburetor
Air control valve
Air gulp valve
Air select valve
Air switching valve
Anti-backfire valve
Anti-percolation valve
Antibackfire valve
Antipercolation valve
Aspirator valve
Back pressure modulated valve
Back pressure valve
Ball valve
Bleeder valve
Bleed valve
Blow-off valve
Blowoff valve
Boost control valve
Boost valve
Brake proportioning valve
Burned valves
Butterfly valve
Bypass valve
Cam follower
Change valve
Check valve
Choke valve
Combination valve
Compensator valve
Control valve
Delay valve
Delivery valve
Discharge valve
Disc valve
Diverter valve
Dropped valve
Dump valve
Eac Valve
Eas Valve
Economizer valve
Egr valve
Electric air control valve
Electric air switching valve
Exhaust valve opens
Exhaust valve
Expansion valve
Four valve
Frequency valve
Fuel injector nozzle
Fuel injector valve
Governor valve
Gulp valve
Hairpin valve spring
Heat control valve
Heat control valve
High pressure relief valve
Hydraulic valve lifter
Idle stop valve
Inlet valve
Intake valve closes
Intake valve opens
Intake valve
Kickdown valve
Kneuter valve
Lightened valve
Load-sensitive proportioning valve
Manifold heat control valve
Manual valve
Metering valve
Modulator valve
Mushroom valve
Needle valve
Negative back pressure modulated valve
Negative back pressure valve
Negative transducer EGR valve
Oil cooler bypass valve
Oil drain valve
Oil filter bypass valve
Oil filter oil filter bypass valve
One-way valve
Outlet valve
Overhead valves
Overrun control valve
Oversize valve guide
Parallel valves
PCV valve
Petcock
Poa suction throttling valve
Pop-off valve
Poppet valve
Power valve
Pressure limiting valve
Pressure regulating valve
Pressure regulator valve
Pressure relief valve
Presta valve
Primary valve
Progressive valve spring
Progressively wound valve spring
Proportioning valve
Quick take-up valve
RAVE valve
Reed valve
Reed valve induction timing
Regulated proportioning valve
Relay valve
Relief valve
Residual check valve
Residual pressure valve
Reverse inhibitor valve
Rotary disc valve
Rotary valve
Running-on control valve
Safety valve
Scavenging valve
Schrader valve
Shift valve
Shuttle valve
Sleeve valve
Slide valve
Sodium-cooled exhaust valve
Sodium-cooled valve
Solenoid valve
Sponge rubber valve
Spool balance valve
Spool valve
Suction throttling valve
Temperature valve
Thermal time valve
Thermal vacuum valve
Throttle valve
Tire valve
Unloader valve
Vacuum reducer valve
Valve-in-head engine
Valve clearance
Valve cover
Valve duration
Valve face
Valve float
Valve grinding
Valve guide
Valve keeper
Valve key
Valve lash
Valve lift
Valve lifter
Valve margin
Valve oil seal
Valve overlap
Valve port
Valve rotator
Valve seat
Valve seat grinding
Valve seat insert
Valve spring
Valve stem
Valve tappet
Valve timing
Valvetrain
Valve umbrella
Variable valve actuation
X-valve

Valve actuation: See
Variable valve actuation

Valve adjusting screw: A screw at the end of a rocker which bears on a pushrod; used to tilt the rocker and thus adjust the valve clearance

Valve and transducer assembly: This type of EGR valve consist of a modified ported EGR valve and a remote Transducer. Works the same way as an integral backpressure transducer EGR valve

Valve angle: A segment of the full circle of a rotary disc valve cut out to admit the fresh charge into the cylinder

Valve aperture: See
Valve hole

Valve assembly: A device through which a tire is inflated. It includes a valve stem, valve core, and valve cap. Also see Control valve assembly

Valve block: See
Control valve assembly

Valve body: Part of the valve assembly containing plungers, pistons, springs, etc.

Valve body housing: A housing which incorporates the bores in which the valve spools slide and the canals which channel the oil flow

Valve body separator plate: A plate sandwiched between two gaskets which separates the upper and lower parts of the valve body

Valve bounce: The bouncing of a valve on its seat due to the valve spring resonating at very high engine speeds. See Bounce. Also called flutter.

Valve bushing: See
Valve guide

Valve cap: A screw-on cap to prevent the entry of dirt and dust into the tire valve. It does not keep the air in -- the Valve core does that.

Valve carburetor: See
Air valve carburetor

Valve clearance: The distance between the small end of the Valve stem and the Rocker arm or Valve lifter. This gap is necessary to compensate for Expansion due to heat. Also called Valve lash.

Valve clearance depression: A recess in the piston crown

Valve closes: See
Exhaust valve closes
Intake valve closes

Valve core: A check valve within a tire air valve which permits air pressure chucks without undue loss of air pressure. The core should not be considered a valve seal.

Valve cover: A long metal lid located on the top of the Cylinder head on vehicles with overhead camshafts. The valve cover is removed when the valves need adjusting. The British term is rocker box or rocker cover.

Valve cover gasket: A gasket between the cylinder head and the valve cover; usually either a flat paper or cork gasket or an O-ring. The British term is rocker cover gasket.

Valve crown: See
Valve head

Valve cut-out: On some four-valve engines at low speed the main rocker arms open only two valves per combustion chamber in order to keep the energy of the gases at a high level; with increasing rpm, the energy of the gases becomes sufficiently strong for the remaining two valves to be opened via hydraulic locking bolts

Valve diameter: Intake valves can be distinguished from exhaust valves by their larger diameter

Valve duration: The length of time, measured in degrees of engine Crankshaft rotation, that a valve remains open.

Valve engine: See
Sixteen valve engine

Valve, expansion: Type of refrigerant control which maintains constant pressure in the low side of refrigerating mechanism. Valve is caused to operate by pressure in low or suction side, Often referred to as an automatic expansion valve or AEV.

Valve extension: Extra length added to a tire valve stem for greater accessibility particularly on inside duals.

Valve face: The outer lower edge of the Valve head. The face contacts the Valve seat when the valve is closed.

Valve float: A condition where the valves in the engine are forced back open before they have had a chance to seat. Brought about (usually) by extremely high rpm. The Valve lifters lose contact with the cam lobes because the Valve springs are not strong enough to overcome the Momentum of the various Valvetrain components. The onset of valve float prevents higher-rpm operation. Extended periods of valve float will damage the Valvetrain. Also called Valve bounce

Valve follower: See
Valve lifter.

Valve gear: A mechanism that operates the intake and exhaust valves; includes the cams, pushrods, rocker arms, etc. but not the valves themselves

Valve grinder: A special automotive tool consisting of a wooden shaft and rubber suction cup(s) for hand grinding valves. Also see Suction valve grinder

Valve grinding: Renewing the Valve face area by grinding on a special grinding machine.

Valve grinding compound: An abrasive compound used for refacing valve seats. The suction cup is placed on the valve head and the valve is pressed into the seat; turning the handle between one's hands will grind the valve into its seat; always use with grinding paste. Not to be confused with valve seat cutter which is used to cut worn valve seats to a specific angle

Valve grinding tool: A special automotive tool consisting of a wooden shaft and rubber suction cup(s) for hand grinding valves

Valve guide: The cylindrical hole which is located in the Cylinder head or Block through which the stem of the Poppet valve passes. It is designed to keep the valve in proper alignment. It also serves as a bearing surface. Some guides are pressed into place and others are merely drilled in the block or in the head metal. Also see Oversize valve guide

Valve guide driver: A tool for installing valve guides

Valve guide reamer: A tool used to enlarge worn valve guides to accommodate oversized valve stems

Valve guide remover: A drift punch for driving out valve guides

Valve guide seal: See
Valve stem seal

Valve head: The surface of the large end of a valve.

Valve hole: The circular opening in the rim of a wheel for mounting tubeless tires. Tubeless car tires commonly have a snap-in valve consisting of a rubber molding bonded to the metal stem casing. The rubber molding has a groove formed at the base; when the valve is pulled through the valve hole, the pliable rubber base snaps into position. Commercial vehicle valves for tubeless tires are all metal; they are attached to the rim and the valve hole by an extended thread formed at the base and secured by a nut. Airtight sealing is achieved by either an O-ring or a fiat and flanged rubber washer. Commercial vehicle valve stems may have a single, double, or triple bend to accommodate different rim profiles and single and twin wheel combinations. On bicycle rims, the hole may be one of two sizes to accommodate Presta or Schrader valves. Also called valve aperture

Valve induction: See
Reed valve induction timing

Valve induction timing: See
Reed valve induction timing

Valve in head engine: See
Valve-in-head engine.

Valve-in-head engine: An engine in which both Intake and Exhaust valves are mounted in the Cylinder head and are driven by pushrods or by an overhead camshaft. Also called I-head engine or Overhead-valve engine.

Valve job: Replacing or regrinding old valves

Valve keeper: A small unit that snaps into a groove in the end of the Valve stem. It is designed to secure the Valve spring, valve spring retaining washer and valve stem together. Some are of a split design, some of a horseshoe shape, etc. Also called Valve key or valve retainer.

Valve key: Key, keeper, washer, or other device which holds valve spring cup or washer in place on valve stem See Valve keeper.

Valve lapper: A special automotive tool for grinding (lapping) valves into valve seats; some types are power-operated, thus allowing faster grinding compared with standard suction-type valve grinding tools

Valve lapping compound: See
Valve grinding compound

Valve lash: Valve tappet Clearance or total Clearance in the valve operating train with Cam follower on Camshaft Base circle. Also see Valve clearance

Valve lift: Distance a valve moves from the full closed to the full open position. It is usually about a quarter of the diameter of the port.

Valve lifter

The cylindrically shaped component that presses against the lobe of a camshaft and moves up and down as the cam lobe rotates. Most valve lifters have an oil-lubricated hardened face that slides on the cam lobe. So-called roller lifters, however, have a small Roller in contact with the cam lobe -- thereby reducing the friction between the cam lobe and the lifter. Also called valve follower or Cam follower.
A tool that compresses valve springs for removal and replacement.
Also see
Hydraulic valve lifter

Valve lock: Key, keeper, washer, or other device which holds valve spring cup or washer in place on valve stem

Valve margin: The width of the edge of the Valve head between the top of the valve and the edge of the face. Too narrow a margin results in Preignition and valve damage through over-heating.

Valve oil seal: A Neoprene rubber ring that is placed in a groove in the Valve stem to prevent excess oil entering the area between the stem and the guide. There are other types of these seals.

Valve opens: See
Exhaust valve opens
Intake valve opens

Valve overlap: A certain period in which both the Intake and Exhaust valve are partially open. The intake is starting to open while the exhaust is not yet closed. It is usually expressed in degrees of crankshaft rotation and determined by the valve timing, valve overlap is necessary for the efficient flow of gases in and out of the combustion chamber

Valve plate: Part of compressor located between top of compressor body and head. It contains compressor valves and ports.; See
Valve body separator plate

Valve port: The opening, through the Head or block, from the Intake or Exhaust manifold to the valve seat.

Valve principle: The original method of ABS control using an electrically operated valve to control the air pressure

Valve retainer: See
Valve keeper.

Valve rotator: A unit that is placed on the end of the Valve stem so that when the valve is opened and closed, the valve will rotate a small amount with each opening and closing. This gives longer valve life. Also called Roto cap

Valve seat

The area onto which the face of the Poppet seats when closed. The two common angles for this seat are forty-five and thirty degrees.
The surface against which a valve comes to rest to provide a seal against leakage.

Valve seat cutter: A special automotive tool with carting blades for use with power tools; used to cut worn valve seats with 30° or 45° angles

Valve seat face: An annular part of a valve head located at the valve seat of the cylinder head

Valve seat grinding: Renewing the valve seat area by grinding with a stone mounted upon a special Mandrel.

Valve seat insert: A hardened steel valve seat that may be removed and replaced. The use of valve seat inserts dispenses with the need for lead in the fuel to act as a lubricant between the valve head and seat Also see Insert.

Valve seat ring: A ring-shaped insert of a harder metal than that of the cylinder head; the use of valve seat inserts dispenses with the need for lead in the fuel to act as a lubricant between the valve head and seat

Valve, service: Device used to check pressures, service, and charge refrigerating systems.

Valve shim: A calibrated shim used to adjust valve clearance on OHV engines with bucket tappet assembly; for adjustment, a calibrated valve shim is placed or removed from between tappet and cam

Valve shim pliers: A special automotive tool for the removal and installation of valve shims

Valves-in-receiver unit: (VIR) a component used on GM system, in which the thermostatic expansion valve, POA suction throttling valve, the receiver-drier, and, if equipped, the sight glass are all combined into one assembly

Valve slot: Tube-type tires require a valve slot instead of a valve hole to allow the tire valve to be removed from the rim; a thread adaptor is molded to a circular rubber patch vulcanized to the inner tube; the valve stem casing is then screwed onto the tube adaptor

Valve, solenoid: Valve made to work by magnetic action through an electrically energized coil.

Valve spool

In an automatic transmission, a sliding cylindrical internal part of a valve with one or more sections of reduced diameter
A spool-shaped valve, such as in the power-steering unit.

Valve spring: A small Coil spring that closes the valve after it has been opened by the cam, and prevents the valve from bouncing on its seat. The action of the spring keeps the Lifter in contact with the cam. If the spring is weak, noise will be generated and the valve, spring, lifter and cam will be subjected to hammer-like blows that cause Metal fatigue.

Also See
Hairpin valve spring
Progressively wound valve spring
Progressive valve spring

Valve spring cap: The retaining cap (of intake or exhaust valves) which secures the valve keeper on the valve stem

Valve spring collar: The retaining cap (of intake or exhaust valves) which secures the valve keeper on the valve stem

Valve spring compressor: A special automotive tool used to compress valve springs for removal and replacement; the most common type is a c-shaped clamp

Valve spring depressor: A lever-type tool used to depress valve springs, e.g., for removal and installation of valve stem seals

Valve spring lifter: A pliers-type tool with two expanding jaws, used to lift and compress valve springs for removal and replacement

Valve spring retainer: See
Valve spring cap

Valve spring seat: A seat retaining the bottom of the valve spring

Valve stem: The long cylindrical portion of the valve that moves up and down in the Valve guide.

Valve stem seal: The oil seal between the valve and the cylinder head which prevents excessive oil leakage from the top of the cylinder head into the combustion chamber

Valve stem seal installer: A sleeve-type tool used to push down valve stem seals for installation

Valve stem seal pliers: A special plier for removing valve stem seals on overhead camshaft engines

Valve, suction: Valve in refrigeration compressor which allows vaporized refrigerant to enter cylinder from suction line and prevents its return.

Valve switch: See
Throttle valve switch

Valve system: See
Vtec Valve system

Valve tappet: An adjusting screw to obtain the specified Clearance at the end of the Valve stem (tappet clearance). The screw may be in the top of the Lifter, in the Rocker arm, or in the case of the Ball joint rocker arm, the nut on the mounting Stud acts in place of a tappet screw.

Valve timing: Adjusting the position of the Camshaft to the Crankshaft so that the valves will open and close at the proper time. Also see Variable valve timing

Valve tip: The upper end of the valve that contacts the rocker arm

Valvetrain: See
Valve train.

Valve train

Click image to supersize
Valve train

The various parts making up the valve and its operating mechanism which causes the valves to open and close.
The system of valves that lets the fuel charges in and let the exhaust gases out.

Valve umbrella: A washer-like unit that is placed over the end of the Valve stem to prevent the entry of excess oil between the stem and the guide. Used in valve-in-head installations.

Valve, water: In most water cooling units. a valve that provides a flow of water to cool the system while it is running.

Van

A covered road vehicle for carrying goods.
A recreational vehicle based on the body of a commercial van, usually with comfortable, plush interior trim, often with a bed.

Also See
Box van
Cube van
Light van

Vanadium Inhibitor: An organic and/or inorganic metal bearing chemical intended to chemically and/or physically combine with the compounds formed during combustion of heavy fuel oil to improve the surface properties of the treated ash compounds.

Van camper: See
Type B motorhome
Class B RV

Van conversions: See Class B RV

Vane: A thin plate that is affixed to a rotatable unit to either throw off air or liquid, or to receive the thrust imparted by moving air or liquid striking the vane. In the first case it would be acting as a Pump and in the second case as a Turbine.

Also See
External vane pump
Hall vane switch
Internal vane pump
Rotary vane pump

Vane air-flow meter: (VAF) a sensor with a moveable vane connected to a potentiometer calibrated to cause the amount of air flowing to the engine

Vane air temperature sensor: (VAT) located inside the vane airflow meter housing; sense the temperature of the air flowing into the engine

Vane-in-rotor pump: A Sliding-vane pump

Vane-in-stator pump: See
External vane pump

Vane pump: A type of rotary pump with either a slotted rotor and sliding vanes or a rotor with hinged vanes; typically used for air pumps in secondary air injection systems, as a compressor in air conditioning systems, and in some transmission systems.

Also See
External vane pump
Internal vane pump
Rotary vane pump

Vanes compressor: Mechanism for pumping fluid by revolving blades inside cylindrical housing.

Vane switch: See
Hall vane switch

Vane wheel impeller: An impeller with straight radial vanes

Vanity mirror: A mirror on the inside of a sun visor

Vanity plate: A personalized licence plate

Vapor

The gaseous form of a liquid which is usually created by heating the liquid.
A gas which is often found in its liquid state while in use.
The gaseous state of refrigerant. Vaporized refrigerant is preferred to the word gas.

Also See
Fuel vapor
Fuel vapor recirculation system

Vapor barrier: Thin plastic or metal foil sheet used in air-conditioned structures to prevent water vapor from penetrating insulating material.

Vapor canister: See
Activated carbon canister

Vapor degreasing: A type of cleansing procedure to remove grease, oil, and loosely attached solids from metals; a solvent such as trichlorethylene is boiled, and its vapors are condensed on the metal surfaces

Vapor deposition: A production of a surface film of metal on a heated surface, usually in a vacuum, either by decomposition of the vapor of a compound at the work surface, or by direct reaction between the work surface and the vapor. Also see Zinc vapor deposition

Vapor displacement: The release of vapors that had previously occupied space above liquid fuels stored in tanks. These releases occur when tanks are emptied and filled.

Vapor injection: See
Water injection.

Vaporization

Breaking the Gasoline into fine particles and mixing it with the incoming air.
Change of liquid into a gaseous state.

Vaporize: The action of converting a liquid into a mist or vapor by breaking it into small particles and mixing it with air. The design of the Carburetor and Fuel injectors vaporizes Gasoline to produce a combustible Fuel-air mixture. If it is not vaporized, the liquid gasoline may not burn properly and may even Hydraulic.

Vapor lines: Air conditioning system lines in which refrigerant is normally in a gaseous or vapor state.

Vapor lock

This is an unwanted condition where bubbles of air form in the fuel line caused by boiling or vaporizing of the fuel in the lines from excess heat. The boiling will interfere with the movement of the fuel and the air bubbles which form will in some cases, completely stop the flow. Sometimes it will cause the Float chamber to overflow which Floods the Carburetor and result in an over-rich mixture that can cause stalling of the engine when the Accelerator is depressed. Fuels containing Alcohol have lower Boiling points and many old-car owners have installed more-powerful electric Fuel pumps which overcome vapor lock tendencies of these fuels by pushing them through the air bubble. A wet rag will cool the line and get rid of the problem. To prevent the problem in hot weather, some mechanics wrap tinfoil around the fuel lines to reflect the heat away.
The abnormal condition that occurs when brake fluid contains too much moisture and is overheated, causing the moisture in the fluid to boil. Gas bubbles are formed in the fluid, which causes a spongy brake pedal or a complete loss of hydraulic pressure.
Condition where liquid is trapped in line because of bend or improper installation. Such vapor prevents liquid flow.

Vapor pressure

Pressure imposed by either a vapor or gas.
The tendency of a liquid to pass into the vapor state at a given temperature. With automotive fuels, volatility is determined by measuring RVP.

Vapor pressure curve: Graphic presentation of various pressures produced by refrigerant under various temperatures.

Vapor recirculation: See
Fuel vapor recirculation system

Vapor recirculation system: See
Fuel vapor recirculation system

Vapor recovery: An emission control system used by gasoline stations. A special filler nozzle seals the gap between the pump filler nozzle and the car's filler opening, preventing benzene vapors from escaping into the atmosphere; instead, they are recycled into the gas station's own fuel tank; the same system is also used when the gas station receives a new delivery of fuel from a gas tanker

Vapor recovery system: A system that prevents the escape of Gasoline vapors from the Fuel system into the atmosphere. The basic system consists of a Canister filled with activated Charcoal and pipes connecting the Canister to the Fuel tank and Carburetor. Any vapor-filled air that leaves the Fuel tank because of Expansion passes through special Emission control pipes to the Canister where the vapors are grabbed and stored by the Charcoal. Then when the engine is started, Intake manifold Vacuum draws fresh outside air up through an opening in the Canister. This moving air pulls the fuel vapor out of the Charcoal and carries it to the Carburetor and into the engine. In the meantime any Gasoline that evaporates from the Carburetor collects in the Carburetor and Air cleaner. As soon as the engine starts this vapor is drawn down through the Carburetor and into the engine along with the entering Fuel-air mixture. Also called evaporative Emission control. See Exhaust emission controls.

Vapor recycling: An emission control system used by gasoline stations. A special filler nozzle seals the gap between the pump filler nozzle and the car's filler opening, preventing benzene vapors from escaping into the atmosphere; instead, they are recycled into the gas station's own fuel tank; the same system is also used when the gas station receives a new delivery of fuel from a gas tanker

Vapor retarder: A material that retards the movement of water vapor through a building element (walls, ceilings) and prevents insulation and structural wood from becoming damp and metals from corroding. Often applied to insulation batts or separately in the form of treated papers, plastic sheets, and metallic foils.

Vapor, saturated: Vapor condition which will result in condensation into droplets of liquid if vapor temperature is reduced.

Vapor separator: A device used on cars equipped with air conditioning to prevent Vapor lock by feeding vapors back to the Fuel tank via a separate line.

Vapor withdrawal: A system of piping and connection to operate an engine directly on vapor taken from the top of an LPG tank

Vapour: British spelling for Vapor

VAR: A unit of reactive power in a circuit carrying a sinusoidal current. A VAR equals the amount of reactive power in the circuit when the product of the root-mean-square value of the voltage (volts) by the root-mean value of the current (amps) and the sine of the phase angle between the voltage and the current, equals 1.

VARI: Acronym for Vacuum Assisted Resin Injection -- a process for forming composite panels and bodywork with consistent, controllable results.

Variable: See
Infinitely variable transmission
Input variable

Variable air volume: (VAV) system on the heating and cooling system: A means of varying the amount of conditioned air to a space. A variable air volume system maintains the air flow at a constant temperature, but supplies varying quantities of conditioned air in different parts of the building according to the heating and cooling needs.

Variable air volume controller: (VAV) Device having electronic components used to regulate the volume of air in a distribution system.

Variable assist power steering: A power steering system that enables the stiffness or tension of the steering to increase at higher speeds for more control or to soften at low speeds when performing slower activities, such as parallel parking. See Variable ratio steering

Variable assist steering: See
Variable assist power steering

Variable belt transmission: A continuously variable transmission using rubber V-belts on expanding-contracting pulleys, depending on engine speed and load; originally developed by van Doorne for DAF and then used on the Volvo 340

Variable-choke carburetor: See
Variable-venturi carburetor

Variable displacement compressor: A compressor which can change its output in accordance with the conditions.

Variable dwell: See
Dwell-angle control

Variable exhaust port: See
Adjustable variable exhaust port.

Variable fuel vehicle: See
Flexible fuel vehicle.

Variable hole cutter: A drill bit with a stepped cutting head used to drill holes into sheet metal and to enlarge the radii gradually by advancing from one step diameter to the next on the same drill bit

Variable intake manifold: A setup in which the path through which air travels into the engine can be altered. Altering the path at a set point allows an engine to develop more power over its rev range.

Variable limited-slip axle/center differential: A limited-slip axle/center differential with an electronically operated multiple-disc clutch as a slip-inhibiting device

Variable pitch pulley: Pulley which can be adjusted to provide different pulley drive ratios.

Variable pitch stator: A Stator that has Vanes that may be adjusted to various angles depending on load conditions. The vane adjustment will increase or decrease the Efficiency of the Stator.

Variable rate springs: Springs which become stiffer under compression; variable rate gas springs are a feature of air suspension systems

Variable ratio steering: Steering ratio characteristics in power steering systems providing different ratios for small and large steering angles

Variable reluctance sensor: (VR or VRS) a non-contact Transducer that converts mechanical motion into electrical control signals

Variable resistor: A resistor, connected in series with an electric motor that can be adjusted to vary the amount of current available and thereby alter motor speed

Variable-speed wind turbines: Turbines in which the rotor speed increases and decreases with changing wind speed, producing electricity with a variable frequency.

Variable spring: Spring providing variable effective length through cam action to suit load.

Variable transmission: See
Continuously variable transmission
Infinitely variable transmission.

Variable valve actuation: In older engines, the Intake and Exhaust valves operated in a fixed program of timed openings and closings. With variable valve actuation, these actions are varied for a better balance of low-speed, medium-speed, and high-speed operation.

Variable valve timing: Through the use of computers, the precise time when the valves open and close can be altered. It may be better to change the timing slightly when the engine is at a higher RPM than when it is slower.

Variable-venturi: See
Air-valve carburetor.

Variable-venturi carburetor: The characteristic feature of this carburetor is the vacuum-operated piston which adjusts the cross-sectional area of the venturi and moves a jet needle in and out of a needle jet; typical designs are the SU and Stromberg carburetors

Variable volume induction system intake configuration: A restrictor plate that opens and closes controlling the amount of oxygen that can go into the engine.

Variomatic transmission: A transmission which used rubber belts and expanding pulleys to provide an infinitely variable belt drive. Also see Variable belt transmission

Varnish

A deposit on the interior of the engine caused by the engine oil breaking down under prolonged heat and use. Certain portions of the oil deposit themselves in hard Coatings of varnish.
Residue formed when Gasoline gets old and stale.

VAT: Acronym for Vane air temperature sensor

VATS: Acronym for Vehicle AntiTheft System

Vauxhall: Click image for books on
Vauxhall

A vehicle brand of which only the 25/70 and 30/98 models of 1925-1948 are Classic cars.

VAV: Acronym for Variable air volume

VAWT: Acronym for vertical-axis wind turbine