Gearhead Engines Glossary: Understanding the Language of Remanufacturing
Whether you’re shopping for a replacement engine or learning about the remanufacturing process, this glossary will help you understand the key terms used across the Gearhead Engines site. From core charges to long blocks and crate engines, here’s everything you need to know to make an informed decision.
A
ABS (Anti-Lock Braking System)
A safety system that prevents wheels from locking during hard braking, helping maintain steering control.
AFM (Active Fuel Management)
A system that deactivates certain engine cylinders during light driving conditions to improve fuel efficiency.
Aftermarket Engine Parts
Engine components made by third-party manufacturers rather than the original equipment manufacturer (OEM). Quality and performance can vary depending on the supplier.
Air-Fuel Ratio
The ratio of air to fuel in combustion. Gasoline engines typically run most efficiently at about 14.7:1.
Align Boring
A precision machining process that restores proper alignment of an engine block’s main bearing bores.
Alternator
A component that generates electrical power while the engine runs, charging the battery and powering vehicle systems.
Axles
Shafts that transfer power from the drivetrain to the wheels and support vehicle weight.
B
Balancing an Engine
The process of equalizing rotating component weights to reduce vibration and improve durability.
Block (Engine Block)
The main structure of the engine that houses the cylinders, pistons, and crankshaft.
Block Decking
Machining the top of an engine block to create a perfectly flat surface for the cylinder head and gasket.
Blown Engine
Severe internal engine failure caused by overheating, oil starvation, or mechanical damage. Usually requires replacement.
Bore and Stroke
Bore is cylinder diameter; stroke is piston travel distance. Together they determine engine displacement.
C
Camshaft
A rotating shaft that controls when engine valves open and close.
Camshaft Specifications (Cam Specs)
Measurements such as lift, duration, and lobe separation that influence engine performance and efficiency.
Carburetor
A device used in older engines to mix air and fuel before fuel injection became standard.
Catalytic Converter
An emissions device that converts harmful exhaust gases into less harmful substances.
Compression Stroke
The phase of the engine cycle where the air-fuel mixture is compressed before ignition.
Connecting Rod
Links the piston to the crankshaft and transfers combustion force into rotational motion.
Core Inspection Process
Evaluation of a returned engine core to determine if it qualifies for a refund.
Crankshaft
Converts piston movement into rotational engine power.
Crankshaft Grinding
Machining process used to restore worn crankshaft journals to proper specifications.
Crate Engine vs. Reman Engine
A crate engine is shipped fully assembled; a reman engine is rebuilt to OEM specifications.
Cylinder Heads
The top portion of the engine that seals the combustion chamber and houses valves, spark plugs, and fuel injectors.
Cylinder Honing
Machining that creates a crosshatch pattern inside cylinders for proper piston ring seating.
D
Diesel Engine
An engine that ignites fuel using high compression instead of spark plugs. Known for durability, torque, and fuel efficiency.
Differential
A drivetrain component that allows wheels on the same axle to rotate at different speeds when turning.
Displacement
The total volume swept by all pistons in an engine, typically measured in liters or cubic centimeters.
Drivetrain
All components that transfer engine power to the wheels, including transmission, driveshaft, differential, and axles.
Dyno Tested
Engines tested on a dynamometer to verify performance and reliability.
E
ECU (Engine Control Unit)
The vehicle’s computer that controls fuel delivery, ignition timing, and engine performance.
EGR (Exhaust Gas Recirculation)
A system that recirculates exhaust gases back into the engine to reduce emissions.
Engine Assembly Process
The installation and torquing of internal engine components according to manufacturer specifications.
Engine Blueprinting
A precision process ensuring engine parts meet exact factory tolerances.
Engine Break-In Period
The first 500–1,000 miles after installation when driving habits and oil changes affect long-term engine life.
Engine Compatibility
Whether a replacement engine matches a vehicle’s year, make, model, VIN, and emissions requirements.
Engine Core
The old engine returned when purchasing a remanufactured unit.
Engine Swap
Replacing a vehicle’s original engine with another engine.
Engine Warranty Coverage
Defines what parts and repairs are covered after purchase.
F
Financing an Engine Replacement
Allows customers to pay monthly instead of upfront.
Flywheel
A heavy rotating disk that smooths engine power delivery.
Fuel Injector
A device that sprays fuel into the combustion chamber for controlled combustion.
G
Gasket
A sealing component placed between engine parts to prevent fluid or gas leaks.
Gear Ratios
The relationship between engine speed and wheel speed that determines torque and vehicle acceleration.
Glow Plug
A heating element used in diesel engines to aid cold starts.
H
Harmonic Balancer
A crankshaft-mounted device that reduces engine vibration.
Head Gasket Failure
Occurs when the seal between block and cylinder head fails, often causing overheating or coolant loss.
Horsepower (HP)
A measurement of engine power output. One horsepower equals 550 foot-pounds per second.
I
Idle Air Control Valve (IACV)
Regulates engine idle speed by controlling airflow.
Ignition Coil
Converts battery voltage into the high voltage needed for spark plugs.
Internal Combustion Engine
An engine that generates power by burning fuel inside cylinders.
L
Liftgate Delivery
Freight service that lowers heavy engines to ground level at delivery.
Limited Slip Differential (LSD)
A differential that improves traction by limiting wheel speed differences.
Line Boring
Machining process restoring main bearing alignment.
Long Block
An engine assembly including block, pistons, crankshaft, and cylinder heads.
Long Block vs. Short Block
Short block = block + internals; long block = short block + heads and valve train.
Low Engine Compression
A condition caused by worn rings, valves, or gasket failure that reduces engine power.
M
Mass Air Flow Sensor (MAF)
Measures air entering the engine so the ECU can deliver the correct fuel amount.
Metal Shavings in Oil
A sign of internal engine wear that may indicate serious damage.
O
Octane Rating
A fuel’s resistance to premature combustion or knocking.
OEM Spec Engine
An engine rebuilt or manufactured to original manufacturer specifications.
Oil Starvation
Occurs when engine parts do not receive enough lubrication, leading to severe damage.
P
Piston
Moves up and down inside the cylinder to generate engine power.
Piston Rings
Seal the combustion chamber, transfer heat, and control oil usage.
Powertrain
The system that delivers power to the wheels, including engine, transmission, and drivetrain.
R
Radiator
Transfers heat from engine coolant to the air to prevent overheating.
Rear Main Seal
Prevents oil from leaking where the crankshaft exits the engine.
Remanufactured Engine
An engine fully disassembled, machined, and rebuilt to OEM or better standards.
Rod Knock
A knocking noise caused by worn connecting rod bearings.
RPM (Revolutions Per Minute)
A measure of how fast the engine’s crankshaft rotates.
S
Seized Engine
An engine that has locked up due to overheating or lack of lubrication.
Serial Number (Engine)
A unique identifier used to track engine specifications and history.
Short Block
An engine assembly including block, pistons, rods, and crankshaft.
Sludge Build-Up
Thick deposits of contaminated oil inside the engine that restrict lubrication and can cause damage.
Spark Plug
Creates the spark that ignites the air-fuel mixture.
Spun Bearing
A bearing that has shifted from its proper position, causing internal engine damage.
Supercharger
A device that forces additional air into the engine to increase power.
T
Throttle Body
Controls the amount of air entering the engine.
Timing Belt or Chain
Synchronizes crankshaft and camshaft rotation to ensure valves open at the correct time.
Timing Chain Failure
Occurs when the chain stretches, slips, or breaks, potentially causing major engine damage.
Torque
A measure of rotational force produced by the engine.
Torque Converter
Transfers engine power to an automatic transmission using fluid coupling.
Torque Plate Honing
Machining process that simulates cylinder head pressure to ensure accurate bore alignment.
Transfer Case
Distributes engine power between front and rear axles in AWD/4WD vehicles.
Transmission
Adjusts gear ratios and transfers power from the engine to the wheels.
Turbocharger (Turbo)
A turbine-driven device that increases engine power by forcing compressed air into the combustion chamber.
V
Valve
Controls intake and exhaust flow in the engine.
Vaporization
The process of turning fuel into vapor for combustion.
VIN (Vehicle Identification Number)
A unique 17-character code used to identify vehicle specifications.
VIN Engine Matching
Ensures the replacement engine matches the vehicle’s VIN for proper fit and emissions compliance.
VVT (Variable Valve Timing)
Technology that adjusts valve timing to improve performance and efficiency.
W
Water Pump
Circulates coolant through the engine to regulate temperature.
