D
deck The surface of the engine block on which the head gasket and cylinder sit.
degreeing a cam Using a dial indicator and a degree wheel to verify that a cam's lift and duration is accurate.
departure angle The maximum angle a truck can descend before hitting the rear bumper or other components located behind the rear tires.
Detroit Locker A popular brand of automatic locking differential.
dial-in 1. To set up a truck's engine, chassis, drivetrain, stereo, or other system so that maximum performance results. 2. To set up a mechanical component for trouble-free operation.
direct ignition system Ignition system that has no distributor; ignition is sent directly from the multiple modulators (coils to the spark plugs).
directional tire Tire with an asymmetrical tread that is designed to produce superior traction when rotating in one direction only.
double-line A type of winch rigging that runs the cable to an anchor point and back to the vehicle, thereby doubling the pulling power.
Double-pumper A four-barrel Holley carburetor with mechanical linkage to open both the primary and secondary barrels and mechanical accelerator pumps in both the primary and secondaries.
drag link Steering link that connects the pitman arm to the steering arm.
droop Any downward suspension travel.
drop the hammer To accelerate rapidly from a stop.
dropped pitman arm An offset arm that lessens the angle between the steering box and drag link.
dualie A truck that has dual rear tires on each side.
dual plane An intake manifold with runners that do not share a common plenum, usually designed for low- to midrange engine performance.
dyno Abbreviation for dynamometer, a machine used to measure engine torque either at the flywheel (engine dyno) or rear tires (chassis dyno).
E
ECU Electronic Control Unit, computer unit for engine management.
EFI Electronic Fuel Injection; computer-controlled fuel delivery system.
EGR Exhaust Gas Recirculation, an emissions-controlled device that reintroduces burned exhaust gases to an engine's combustion chamber.
electronic ignition Ignition system that uses transistorized circuits instead of breaker points.
E.O. Number Executive Order Number, the number assigned to a part by the California Air Resources Board when it becomes legal to use on emissions-controlled vehicles.
exhaust backpressure Resistance to the free flow of exhaust gases through an exhaust system
exhaust headers Performance exhaust manifold built from equal-length steel tubes that is designed to speed the flow of exhaust gases exiting the cylinder head(s).
exhaust manifold Tubular cast-iron component that routes exhaust gases from the cylinders to the exhaust system.
F
fairlead A steel guide installed onto a winch mount to help direct the winch cable. Fairleads come in two styles: roller, which uses steel rollers, or Hawse, which features a simple bracket with large radiused edges for the cable to ride against.
fan clutch Thermostatically controlled clutch device that engages or disengages a mechanical radiator cooling fan according to the engine's cooling needs.
flathead An early engine design that located the valves in the block beside the cylinders, rather than the head (overhead valves) as is currently done.
flat spot Momentary decrease in engine power at some point within the powerband.
flat-top 1. A piston without a dish or a dome. 2. A popular '50s haircut.
forced induction Supercharged or turbocharged
four-banger A four-cylinder engine.
four-bolt main A crankshaft's main bearing caps held in place by four bolts.
freewheeling When the front hubs are unlocked and the wheels spin because of momentum rather than power.
fuelie Old slang referring to a fuel-injected engine or vehicle.
fuel injector Electromechanical device that squirts fuel into an engine.
full-floater An axle assembly designed to hold the weight of the vehicle on the axlehousing instead of on the axleshafts; has bearings at both the differential and wheel ends.
G
gas shock Damper shock absorber with two separate compartments, one containing hydraulic fluid, one containing nitrogen gas. The gas keeps pressure on a flexible, in some cases, moveable separating disc, that, in turn, keeps pressure on the fluid, thereby reducing the fluid's tendency to foam during aggressive driving.
g-force Measurement of the force generated during cornering, acceleration, or deceleration, expressed in units of gravity.
glasspacks Tubular style of muffler that uses fiberglass packing to absorb sound.
gnarly A difficult portion of a trail that may or may not make you nervous. Syn. exceptional.
granny gear An extremely low First gear in a manual transmission. For example, an SM465 has a 6.55:1 First gear ratio.
grenade Catastrophic failure of an expensive part. Engines, transmissions, and axle assemblies can all grenade.
greenhouse Upper portion of a truck's body; the structure above the beltline, including the roof, windows, and pillars. Syn. office.
ground effect Reduced airflow under a truck provided by an air dam and side skirts. Less pressure underneath a truck allows the air passing over its top to push downward, thus creating an improved grip on the road as well as improved top speed and fuel efficiency. Impedes ground clearance in 4x4s.
gumbo Deep, sticky mud.
gun it To deliberately rev an engine.
gusset Triangular metal support used to add strength; is welded in place where two framerails connect or where two tubes of a rollcage are welded together.
GVWR Gross Vehicle Weight Rating, the combined weight of a vehicle and its rated cargo capacity.
H
halogen light High-output headlight or driving light that has halogen gas inside the bulb. When surrounded by a halogen gas, the bulb's tungsten filament can carry a higher current, thus producing a more brilliant white light.
hammered 1. A truck that's thoroughly destroyed. 2. A truck that has a chopped top or a severely lowered suspension.
handle The nickname you use on the CB.
H.E.I. High-Energy Ignition, a powerful and reliable GM distributor assembly with a self-contained coil.
Heliarc welding A form of tungsten inert gas welding used primarily on aluminum and stainless steel.
Helicoil Stripped thread repair system, consisting of small coil-spring inserts that thread into place on damaged female screw threads.
high-centered When a truck is firmly stuck, usually caught on its frame on an obstacle unable to move.
high-pinion See reverse-rotation.
hi-Po High-performance.
hole shot Beating a competitor at the start of a race; coming off of a dead stop quicker; coming out of the hole quicker.
hook up 1. To gain traction. 2. To gain a date.
hub Wheel mounting surface.
huffer A beltdriven supercharger.
hydraulic'd Past tense only, said of an engine that has been submerged in water and has sucked water into its cylinders through the intake and will no longer rotate because the pistons moving up the cylinders cannot compress the water.
I
IFS Independent Front Suspension, a type of suspension system that allows the two tires on one axlehousing to move separately from one another.
intake ports Passages within a cylinder head that route air and fuel to the intake valves.
J
juicebox An automatic transmission.
K
kick-down Quick downshift on an automatic transmission when the engine is given full throttle.
kicker shocks Shocks mounted in a near horizontal position between the axlehousing and the leaf springs. Kicker shocks are valved with a high rate of compression damping and are intended to reduce axlewrap.
kick-up Section of a frame that is curved up to clear an axlehousing.