Chapter Six: Engine Components
Terms in this set (40)
a bearing constructed with balls or rollers between journal and bearing surfaces to provide rolling instead of sliding friction
Automatic Compression Release
a mechanism on the camshaft designed to lift the exhaust valve slightly during cranking to release part of the compression pressure
Shaft containing lobes or cams that operate engine valves.
Piston rings designed to provide a strong seal, keeping the compressed air-fuel mixture and the burning gases above the piston by preventing passage between the piston and the cylinder wall.
Link that attaches the piston to the crankshaft.
Thin metal projections on the cylinder block that increase the surface area around the outside of the cylinder on air-cooled engines.
The housing for the crankshaft and other related internal parts.
Seals that prevent leakage of oil from the areas where the crankshaft and crankcase come together.
The major rotating part of the engine. It converts the reciprocating (back-and-forth) motion of the piston into rotary (circular) motion.
The offset portion of the crankshaft measured from the centerline of the main bearing bore to the centerline of the connecting rod journal.
The portion of the engine block that contains the cylinder bore.
Casting of iron or an aluminum alloy designed to keep all engine parts in alignment.
piston rings installed with the ring end gaps staggered to avoid gap alignment and possible oil flow through the series of gaps to the combustion chamber
A heavy wheel fastened to one end of the crankshaft to improve the running quality of the engine. The inertia of the flywheel keeps the crankshaft spinning and smoothes engine operation.
a bearing that uses a smooth, sliding surface to reduce friction between moving parts
the full-diameter ridges between the piston grooves
Oil Control Rings
Piston rings designed to remove surplus oil from the cylinder walls.
Overhead Cam (OHC)
a valve train arrangement in which both the camshaft and valve assemblies are located in the cylinder head
Overhead Valve (OHV)
a valve train arrangement in which the camshaft is installed in the crankcase and the valves are installed in the cylinder head
the section of the piston surrounding the piston pin hole. It is thick and often reinforced with cast-in webs
a piston ring that is held in position by a short pin that fits into the piston ring groove. The pin prevents rotation of the ring around the groove
a part that moves up and down in the cylinder in order to draw air-fuel mixture into the cylinder during the intake stroke, compress the mixture during the compression stroke, transfer force to the crankshaft during the combustion stroke, and force exhaust out of the cylinder during the exhaust stroke
the journal for the bearing in the small end of an engine connecting rod. The piston pin also passes through the piston walls, holding the piston to the connecting rod
a circular ring that fits into a piston groove and exerts tension on the cylinder wall. Piston rings prevent blowby of exhaust gases into the crankcase and leakage of oil into the combustion chamber
The part of the piston below the rings and the bosses.
A valve structure consisting of a circular head with an elongated stem attached in the center.
a connecting link in an operating mechanism, such as the rod between the valve lifter and rocker arm on an overhead valve engine
Rewind Starter Assembly
Mechanism mounted above the flywheel on many small engines that spins, or cranks, the engine during starting.
the force that a piston ring exerts on the cylinder wall
a device used in an overhead valve system to transfer the upward motion of the pushrod to a downward force on the valve
space that allows piston rings to move in and out of the piston ring grooves while maintaining tension on the cylinder walls
side-to-side movement of the piston in the cylinder caused by too much clearance
Fasteners that are compressed and placed in grooves in the piston pin bosses. They prevent the pin from rubbing on the cylinder surface.
The part of the block in a small four-stroke engine that holds and collects the lubricating oil.
the sides of the piston forced against the cylinder wall. These surfaces are at right angles (90 degrees) to the centerline of the crankshaft and piston pin
Hole machined in the engine block to align the valve and ensure accurate raising and lowering in relation to the seat.
A rod or plunger that transfers motion from the cam and the other valve train components.
a spring attached to a valve to return it to the seat after it has been released from the lifting or opening operation
all components that work together to transform the rotation of the crankshaft into the opening and closing of the valves
a valve train arrangement in which the camshaft is located in the crankcase and the valves are located in the cylinder block, directly above the camshaft lobes
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