Appendix I Glossary

APPENDIX 1 GLOSSARY ACCELERATING PUMP—A device in the carburetor that supplies an additional amount of fuel, temporarily enriching the air-fuel mixture when the throttle is suddenly opened ACCELERATION—The process of increasing velocity. Average rate of change of increasing velocity, usually in feet per second. AIR BLEED—An opening into a gasoline passage through which air can pass (or bleed) into the gasoline as it moves through the passage. AIR CLEANER—A device mounted on the engine through which air must pass before entering the combustion chamber. A filtering device in the air cleaner removes dust and dirt particles from the air. AIR-COOLED ENGINE—An engine cooled by air circulating between cylinders and around cylinder head. AIR FILTER—A filter through which air passes, and which removes dust and dirt particles from the air. AIR-FUEL RATIO—The ratio between the volume of air and the volume of fuel used to establish a combustion mixture. AIR-INJECTION SYSTEM—A system which injects air into the exhaust manifold or thermal reactor so that the combustion of the carbon monoxide and unburned hydrocarbons in the exhaust gases can be completed. AIR POLLUTION—Contamination of the air by natural and manufactured pollutants. AIR PRESSURE—Atmospheric pressure (14.7 pounds per square inch at sea level) or pressure of air produced by pump, by compression in engine cylinder, and so on. ALLOY—A mixture of two or metals, usually produced to improve characteristics of the base metal. ANCHORED PISTON PIN—A stationary wrist pin secured to the piston at the bosses that allows the connecting rod to move about the pin. ATDC —After top dead center. ANTIFREEZE—A substance added to the liquid- cooled engine to prevent freezing. ANTIFRICTION BEARING—Type of bearing in which moving parts are in rolling contact; ball, roller, or tapered roller bearing. ANTIKNOCK—Refers to substances that are added to gasoline to decrease the tendency to knock when the air-fuel mixture is compressed and ignited in the engine cylinder. ATOMIZATION —The spraying of a liquid through a nozzle so that the liquid is broken into tiny globules or particles. AUTOMATIC CHOKE—A choke that operates automatically in accordance with certain conditions, usually temperature and intake manifold vacuum. BABBIT—An antifriction metal lining used as a wearing surface for bearing to reduce the friction between moving components. BACKFIRING—Pre-explosion of air-fuel mixture so mat explosion passes back around the opened intake valve and flashes back through the intake manifold. BACK PRESSURE—The resistance of gases to flow through a system. BAFFLE—A plate or shield to divert the flow of liquid or gas. BALL-CHECK VALVE—A valve consisting of a ball and seat. Fluid can pass in one direction only; it is checked by the ball seating on the seat. BBDC—Before bottom dead center. BDC—Bottom dead center; the position of the piston when it reaches the lower limit of travel in the cylinder. BEARING—A mechanical component that supports and aligns the location of another rotating or sliding member. AI-1