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Boots

Performance term for tires.

Borden Tube

A thermo-mechanical device in the fuel injection system that regulates the amount of fuel being injected according to differences in temperature and pressure in the intake manifold.

Borderline Lubrication

1. Poor lubrication as a result of greasy friction. 2. Moving parts coated with a thin film of lubricant.

Bore

1. The diameter of an engine cylinder. 2. To increase the diameter of a cylinder.

Bore

A cylinder--i.e., a cylindrical hole in an engine block into which a connecting rod and piston are placed. The term also refers to the specific diameter of the cylinder. An engine that has been bored or overbored has larger-than-stock bores.

Bore Align

To machine an engine's main bearing journals to assure they are in perfect alignment.

Bore Centers

The center-to-center distance between two bores.

Bore In The Water

To bore a cylinder out far enough to brake through the water passage.

Bored And Stroked

A combination of an enlarged cylinder bore and a lengthened piston stroke to increase an engine's displacement.

Boss

1. The reinforced extension on a part that holds a mounting pin, bolt, or stud. 2. A slang term for outstanding quality.

Bottle Warmer

A heater for a nitrous bottle that is designed to maintain the proper temperature, so that the contents will be at the ideal pressure. A bottle blanket also can be used to stabilize the bottle at the desired temperature.

Bottom

1. The underside; the lowest part. 2. When a vehicle's chassis hits the lowest point allowed by its suspension system. 3. When the springs are fully compressed.

Bottom Dead Center

A piston's lowest position in a cylinder.

Bottom Dead Center (BDC)

Piston position at bottom of stoke.

Bottom End

The crankshaft main bearing and connecting-rod bearing assembly in an engine.

Bottom Gear

English term for 1st Gear

Bottom Out

If a race car settles down tightly on its springs on an oval track as it travels through a baked turned, centrifugal force tends to push the car downward, toward the track's surface, causing its chassis to "bottom out."

Bottom U-bolt Plate

A plate that is located on the bottom side of the spring or axle and is held in place when the U-bolts are tightened.

Bottom Valve

A shock absorber component to control the flow of oil into the reservoir during compression and rebound.

Bounce Back

A condition that occurs when particles of paint sprayed on a body panel bounce away from the surface.