Engine Glossary

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Engine Glossary

Post by Amskeptic » Sat Jan 14, 2012 11:01 am

********** Engine **********

Turns Over (cranks) - engine spins with starter motor but doesn't fire

Catches - sporatic combustion events and kicking but not running

Backfire - combustion that blasts out the tailpipe, loud sometimes smoke

Pop - combustion that comes up the carb, muted by air filter if on, scary pow if air filter is off ... good idea to keep cranking to suck any flame back into the engine

Ping - can be a subtle rattle sound, but it is very damaging detonation under full load due to overheat or advanced timing

Rattle - can be a dumb loose bracket or tin, or internal part failure, like loosening valve clearances

Knock - dumb loose large part hitting, or dangerous internal large part loosening up, like connecting rod bearing failure or worn main bearings

Tick - most usually a benign loose valve/hydraulic lifter

Thump - out-of-round tires dragging out-of-round brake drums/rotors, loose or damaged shock bushings

Whine - electrical interference through radio, bad alternator/generator bearing, bad transmission bearing, fresh generator commutator (benign)

Whistle - benign air flow sound through FI throttle body, vacuum leak, fresh air leak through seals or ventilation

Whir - cam gear mesh, distributor bushings, generator/alternator brushes, foreign object rubbing v-belt

Surge - a noticeable change in power output while accelerating

Miss - either intermittent or steady negative pulse most usually indicating a loss of spark or dead cylinder

Hesitate - a full engine intermittent loss of power

Lean - insufficient fuel at the combustion chambers > low power and hesitation, gets worse as engine warms up

Rich - too much fuel at combustion chambers causes stumbling and low power but can run really well when cold

Overrun - any time the car is pushing the engine, as in engine braking

Accelerate - when engine or car is increasing in rpm or speed

Decelerate - when engine or car is losing rpm or speed

Light throttle - just off idle operation or slow rate of acceleration

WOT (Wide-Open Throttle) - pedal-to-the-metal full acceleration where engine vacuum is at its lowest

Clearance - the space required for parts to function through expansion and contraction based changes of dimension, usually measured in thousandths of an inch

Play(end-play) - the space required for parts to function through expansion or contraction or load

Slop - unintended clearances or play due to wear
Preload - the intentional running of parts under contact load, like steering gear or differential ring and pinion

Seize - the unintended bonding of two parts that wish they didn't > most usually under heat and friction

Grenade - colloquial term describing the destruction of a complex assembly like an engine or transaxle where destroyed parts destroy other parts > necessitates a rebuild or replacement of engine

Valve Drop - a catastrophic release of a valve from its retainer where it falls into the piston > necessitates a rebuild

Seat recession - the movement or erosion of the hard steel ring that seals valves in the cylinder heads > necessitates a rebuild

Smokes - the burning of oil either through the engine or on hot surfaces

Drips - usually oil sometimes gas or brake fluid or gear oil > always investigate

Flooding - the uncontrolled dumping of gasoline into the carburetor or the rich stall of an engine due to too much fuel delivery

Starvation - inadequate fuel (or oil supply > a dangerous condition)

TDC (Top Dead Center) - piston at the very top of the cylinder, an important reference point for timing the spark or setting parts to be synchronized with each other

BTDC (Before Top Dead Center) - the movement of the crankshaft in degrees before the piston arrives at the top of the cylinder

ATDC (After Top Dead Center) - the movement of the crankshaft in degrees after the piston goes down the cylinder
Combustion Chamber- the specially shaped portion of the cylinder heads where the valves and spark plug reside and combustion is enhanced

Thrust Bearing - any surface that has to resist axial movement of a rotating part

Bearing Saddle - the structure under main bearings that supports and absorbs combustion and rotational forces

Bearing Inserts - replaceable surfaces that ride against rotating parts

Bearing over/undersize - optional size replacement bearings that are matched to reconditioned machined under or over-sized rotating parts
BobD - 1978 Bus . . . . . . . . . . . 112,660 miles
Chloe - 1970 bus . . . . . . . . . . . 206,845 miles
Naranja - 1977 Westfalia . . . . . 112,885 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,899 miles

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