Glossary
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ANTI-PUMP-UP TAPPET: The Iskenderian Hydraulic tappet which automatically bleeds off trapped lifter oil through a patented relief port when the lifter pumps up due to accidental over revving of the engine.ANTI-THRUST BEARING: A special needle bearing secured to the cam sprocket or gear which prevents axial float of the camshaft into the timing case cover at high speed. This condition can drastically change ignition timing as well as damage the cam and engine.
AREA UNDER THE HORSEPOWER CURVE: The area the horsepower curve envelops when plotted graphically from dynamometer torque and rpm readings.
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BARREL SPRING: A valve spring design by Iskenderian which visibly resembles the shape of a barrel, being slightly smaller in diameter at each end than at the center.BASE CRICLE: The concentric or round portion of the cam lobe where valve lash adjustments are made (also called the heel).
BLOWER (or supercharger): A mechanical device which forces greater quantities of fuel and air into the engine's cylinders by means of rotating impellers which are driven from the power of the engine. The 2 most common types are centrifugal and Roots (GMC type). Also called forced induction.
BLOWN: Refers to a supercharged engine.
BOOST: The amount of pressurized air forced into the engine by the supercharger, measured in lbs. per sq. in. or on the barometer in inches of mercury. One lb. per sq. in. equals approximately 2 inches of mercury on the barometer. Atmospheric pressure at sea level is approximately 15 lbs. per sq. in. and most of today's supercharged engines raise this pressure to approximately 30 lbs. per sq. in. or 2 atmospheres.
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CALIBRATED CRANKSHAFT HUB: A hub calibrated in degrees so that ignition and cam timing may be accurately determined.CAM COMPARATOR: This expensive equipment compares and evaluates production cams to a precision master cam to check any possible variation.
CAM CONTOUR: See "CAM PROFILE."
CAM FOLLOWER: Usually a roller or flat faced companion to the camshaft that transfers the action of the camshaft to the rest of the valve train by sliding or rolling on the cam lobe surface.
CAM MASTER: After the design of the cam is computed, it's transferred to a precision template or master. The master is then installed in the cam grinding machine to generate the shape of the lobes of the production cam. The lobes on the master are 5 times that of a regular camshaft so that any variance from the actual computed profile is reduced 5 times.
CAM PROFILE: The actual shape of the cam lobe. At Iskenderian, these profiles are determined by an IBM computer.
CAMSHAFT: A shaft containing many cams that convert rotary motion to reciprocating (lifting) motion. For every 2 revolutions of the crankshaft, the camshaft rotates 1 revolution. The lobes on the camshaft actuate the valve train in relation to the piston movement in an internal combustion engine.
CARBURIZING: Gas carburizing is a method used by Iskenderian to heat treat steel camshaft billets. In this method the camshaft is placed in a gas-carbon atmosphere furnace and heated to the proper temperature. When the shaft has absorbed the proper amount of carbon it's removed from the furnace and quenched to the proper temper.
CAST BILLET: A term used by lskenderian to describe a camshaft which is made from a casting. The material for the casting is a special grade of iron alloy called Proferal."
CHILLED IRON LIFTER: A cam follower made from high quality iron alloy that is heat treated by pouring the molten iron into a honeycomb mold with a chilled steel plate at the bottom to heat treat the face of the lifter. It's compatible with steel and hardface overlay cams only.
CLEARANCE RAMPS: The portion of the cam lobe adjacent to the base circle which lifts at a constant slow speed (usually .00035-00055 in. per degree of cam rotation). Its purpose, in theory, is to compensate for small deflections and take up the slack in the valve train created by the valve lash.
COIL BIND: A valve spring that has been compressed to the point where the coils are stacked solid and the spring's downward movement has stopped.
CONCENTRIC: Running true or having the same center. In camshaft terminology the cam bearings and lobes are concentric to each other when the cam is straight and there is .001 or less runout between all cams and bearings.
CORE DIAMETER: The diameter of the camshaft as measured between the cam lobes.
CORRECTION GRINDING: The process by which another manufacturer's camshaft is reground and corrected to the perfect geometric coordinates of an lskenderian design.
COUNTER-BORING HOLE SAW: When installing high performance large diameter valve springs, it's sometimes necessary to enlarge the spring bases on the head by using this type of tool.
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DESMODROMIC: A special and complex type of valve train. Each valve is operated by 2 lobes . . . 1 lobe opens the valve, the other lobe closes; therefore no springs are used to return the valves to their seats.DREAM WHEEL: A name for the Iskenderian Ratio Computer. Accurately converts MPH to RPM, or RPM to MPH . . . Set gear ratio desired opposite tire diameter, and read MPH opposite engine RPM. The dream wheel resembles a circular slide rule.
DURATION: The amount of time measured in degrees that the valves are off their seats during the lifting cycle of the cam lobe.
DYNAMOMETER: An apparatus for measuring the torque of an automobile engine at various rpm. This torque reading is then converted to horsepower.
DYNO: An abbreviated word for dynamometer.
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ECCENTRIC: A disc having its axis of revolution out of its center of figure -- used for reciprocating or lifting motion. The lobes of the camshaft are eccentric to the cam bearings.
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FITTED DIMENSION: Referring to valve springs, this is the same as installed height of the spring from its base on the cylinder head to its seat at spring retainer.FLAME HARDENING: A heat treating process whereby a camshaft is exposed to an open flame and then quenched (cooled in oil).
FLANKS: The sides of the cam lobe, or the portion of the lobe that lies between the nose and the base circle on either side.
FORCED INDUCTION: See 'SUPERCHARGER."
FORGING: A metal object which was formed under pressure while in a red hot or semi-molten state.
4130: A common grade of chrome-moly steel. The 41 represents the molecular structure of chrome-moly steel, and 30 represents 301100 of 1% of carbon present in the material. This carbon factor determines to what degree the material may be heat treated.
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GEAR DRIVE: A special camshaft drive employing gears in lieu of the common timing chain. The gear drive eliminates cam and distributor timing changes due to wear or stretch of the stock timing chain. The gear drive gives immaculate (precision- perfect) timing.GILMER BELT: A trade name for a flat rubber cog belt used to drive superchargers. The rubber belt has a core of steel wire for reinforcement and the inner side of the belt has evenly spaced cogs which match grooves machined in the supercharger drive pulleys.
GILMER PULLEY: A trade name which is used in conjunction with the Gilmer belt. The pulley has grooves machined into it to mesh with the cogs on the Gilmer belt.
GROOV-MATIC "O" RING TOOL: A tool designed and manufactured by Iskenderian to cut a groove around the cylinder. After the groove is cut, copper wire is inserted so that .010 of the wire is above the plane of the block. The purpose of the raised portion of wire is to increase the pressure on the head gasket around the cylinder to prevent pressure leaks when supercharging the engine.
GROSS LIFT: The theoretical valve lift obtained by multiplying the cam lift by the rocker arm ratio.
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HARDENABLE IRON LIFTERS: A cam follower made from high quality iron alloy. Manufactured with the latest electronic furnace techniques, this the cam bearings and lobes are concentric to each other when the cam is straight and there is .001 or less runout between all cams and bearings.HAROFACE OVERLAY: A process originated by Ed Iskenderian to apply a tungstencarbide, chrome-nickel alloy to the outer surface of the cam lobe. These combined alloys provide an extra-durable surface for the tremendous spring pressures and high rpm of today's all-out competition engines. Camshafts that have been hardfaced are for maximum competition only, and cannot be used on the street.
HEAVY DUTY SPLIT VALVE LOCKS: A component which resembles a semiconical form on the outside. The inside of the cone is notched to coincide with the grooves on the top of the valve. The valve locks prevent the valve from slipping through the spring retainer. Iskenderian is the only company that manufactures special chromemoly locks which replace the stock stamped steel part.
HEEL OF THE LOBE: Same as the "BASE CIRCLE" or the concentric portion of the cam lobe.
HOLE SAW: See "COUNTER-BORING HOLE SAW."
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INERTIA RAM: A condition created by the piston as it reaches the bottom of its intake stroke, by which the inertia of the intake air column continues to pack the cylinder until the pressure exceeds that of the atmosphere.INNER VALVE SPRING: For many racing applications a single valve spring may not exert adequate pressure on the valve train and valve float may occur. Isky engineers have determined the spring pressures necessary for each of our grinds and when this pressure cannot be obtained with 1 spring, a smaller inner spring is used inside the larger outer spring.
INTERFERENCE FIT: In a dual spring combination where the O.D. of the inner spring and the 1.0. of the outer spring nearly approximate each other so that there is a slight press fit between the 2 springs. This produces a dampening effect on valve spring vibration and surge.
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LIFTER: See "CAM FOLLOWER." LIFT GRAPH: By installing the camshaft in a bare block, the mechanic can plot the lift of the cam in relation to each degree of camshaft rotation by installing a dial indicator on the cam follower or tappet and a degree wheel on the crankshaft. All that is necessary is to rotate the crankshaft every 5 degrees and take a reading on the dial indicator at each of these intervals and transfer the readings to graph paper.LOBE: The lobe is eccentric to the cam bearings of the camshaft and transmits a lifting motion through the valve train to operate the valves. The design of the lobe determines the usage of the camshaft - i.e., street use, all-out competition.
LOBE CENTERS: The distance measured in degrees between the center line of the intake lobe and the center line of the exhaust lobe of the same cylinder.
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MICRO SPRING SHIMS: These shims serve the same function as the regular spring shims except they are offered by Iskenderian in .005 increments. By combining different thicknesses, the mechanic can precisely adjust spring height and pressure.MUSHROOM LIFTER: Serves the same purpose as a regular lifter (flat tappet) but is a different shape. The face of the lifter (the area that contacts the cam) is of a larger diameter than that of the lifter body - . - it vaguely conforms to the shape of an inverted mushroom.
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NET LIFT: The actual lift of the valve. This lift can be approximated by subtracting the valve lash dimension from the gross lift figure in the catalog. Production tolerances on rocker arms can vary this figure as much as ±.O1O.NORMALLY ASPIRATED: An engine that utilizes either carburetors or fuel injection without a mechanical device that forces the fuel/air mixture into the combustion chambers (non-supercharged).
NOSE OF LOBE: The highest portion of the cam lobe off the base circle (full lift position).
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OFFSET BUSHINGS: An eccentric bushing placed in the cam gear or sprocket to advance or retard the camshaft with relation to the crankshaft. The dowel pin hole in the cam gear or sprocket is drilled oversize to accept this bushing.OFFSET KEY: A stepped key which is used to advance or retard the camshaft where the cam contains a keyway rather than a dowel pin. Offset keys are also used on the crankshaft to vary cam timing.
OHV: Abbreviation for over head valve." OUTER VALVE SPRING: In a dual spring combination the outer valve spring is always the larger of the 2 springs. It's usually made from a heavier wire than that of the inner spring.
OVERLAP: A situation where both the intake and exhaust valves are open at the same time when the piston is at (TDC).
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PARKERIZING: A thermo-chemical application whereby a non-metallic, oil absorptive coating is applied to the outer surface of the camshaft. This permits rapid break in without scuffing the cam lobes.PISTON NOTCHING TOOL: Today's high lift camshafts often bring the engine's valves too close to the piston crown. Therefore, it's necessary to cut deeper notches in the piston crown to allow adequate valve-to-piston clearance, and prevent the valves from striking the pistons. (Minimum recommended clearance is 100.) POLY LOCKS: A valve train component which replaces the stock adjusting nuts on Chevrolet, Pontiac and Ford rocker arms. These Poly-Locks allow for a finer and more secure adjustment over a wider range and can be used with either mechanical or hydraulic tappets.
PRE-LOAD: To load before applying a different load as with the Isky UltraRev Kit which pre-loads the roller tappets to the cam lobe to keep them in constant contact.
PROFERAL IRON: A very high quality cast iron alloy. Used primarily for camshafts because of its excellent wearing ability.
PUSHROD: A component of the valve train which connects the tappet and rocker arm in an OHV engine. Iskenderian pushrods are manufactured from seamless chrome-moly tubing and come either adjustable or non-adjustable. They are also of special wall thickness for highest strength and lightest possible weight.
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RATIO COMPUTER: See "DREAM WHEEL."REFINISHING: A process by which the cam face is refinished to the same geometrical shape, however, being slightly smaller in size.
REGRINDING: Refers to an operation where a stock camshaft is modified to racing specifications. This should only be done where it is difficult to obtain new cores, as with imported cars.
REV LUBE: A non-detergent lubricant containing Molybdenum-Disulphide which is spread on the cam lobes when installing a camshaft to prevent galling and insure protection during the critical break-in-period - the first 5 minutes of operation.
ROLLER TAPPET: The roller tappet performs the same function as the mechanical or hydraulic tappet. However, instead of sliding on the cam face, the lifter contains a roller bearing which rolls over the cam surface. Its main advantage is that its operating range is very flexible and can be used for street and strip, low or high speed performance.
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SCREW-IN STUDS: Some engines are equipped with press-in studs from the factory for locating and attaching the rocker arms. Under racing conditions, these studs are prone to pulling out and must be replaced with screw-in type rocker arm studs.Installation requires removal of the old studs and tapping the stud holes with a special tap supplied with the installation kit.
SEAT BOUNCE: When there is a lack of valve spring tension, or where a poorly designed cam having excessive deceleration and velocity characteristics is used, the valve lands with such force on the valve seat that it has a tendency to bounce on impact, causing a loss of compression and power in the cylinder.
SOLIDS: Purely mechanical cam followers. This follower or tappet requires either adjustable pushrods or adjustable rocker arms to obtain the required valve lash.
SPLIT OVERLAP: An occurrence when both the intake valves and exhaust valves are off their seats at the same time and the same distance. At this time, the TDC mark on the harmonic damper should correspond with the pointer on the engine.
SPRING FATIGUE: Valve springs have a tendency to lose tension after being run in an engine for certain periods of time, because of the tremendous stress they are under. At 6000 rpm, for example, each spring must cycle 50 times per second. The tremendous heat generated by this stress eventually effects the heat-treating of the spring wire and causes the spring to take a slight set (drop in pressure).
SPRING HARMONICS: See "SPRING SURGE."
SPRING HEIGHT: See "FITTED DIMENSION."
SPRING PRESSURE: The force exerted by a valve spring as it is compressed (measured in pounds per sq. in.).
SPRING RETAINER: A stepped type washer made of either steel, titanium or aluminum that transfers the force exerted by the compressed valve spring to the valve.
SPRING SHIM: A thin metal washer which is placed between the spring seat and the head. Its purpose is to compress the spring to the correct installed height and tension.
SPRING SURGE: The factor which causes unpredictable valve spring behavior at high reciprocating frequencies. It's caused by the inertia effect of the individual coils of the valve spring. At certain critical engine speeds, the vibrations caused by the cam movement excite the natural frequency characteristics of the valve spring and this surge effect substantially reduces the available static spring load. In other words, these inertia forces oppose the valve spring tension at critical speeds.
STACK SOLID: Refers to valve springs. See 'COIL BINDING."
STEEL BILLET: A solid piece of steel bar stock from which Iskenderian machines most of their roller tappet camshafts.
SUPERCHARGER: A mechanical device which forces greater quantities of fuel and air into the engine's cylinders by means of rotating impellers which are driven from the power of the engine. The main types are centrifugal, Roots (GMC type) and vane.
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ULTRA REV KIT: A device designed by Ed lskenderian .to preload the roller tappet to the camshaft to allow higher rpm. The kit consists of 2 plates which are located on each side of the valley chamber and a spring for each roller tappet. The springs fit between the roller tappet and the valley plate.V
VALVE: A mushroomed shaped object which is used to regulate the incoming fresh air! fuel mixture and the outgoing exhaust gases in the cylinder of an internal combustion engine.VALVE EVENT: The opening and closing points of the valve with relation to the crankshaft.
VALVE FLOAT: A detrimental condition caused by over revving of the engine, or by inadequate spring pressure, resulting in a lag of the valve gear components where they fail to follow the dictates of the cam profile. Under this condition the valve is a greater distance off its seat than it normally would be, causing a loss in compression and power, as well as possible damage to the engine if the floating valve strikes the oncoming piston.
VALVE GEAR: Same as "VALVE TRAIN."
VALVE LASH: Same as valve clearance. Valve lash is necessary to allow for thermal expansion of the valve train components during operation.
VALVE SPRING DAMPER: A flat wound spring coil inside the outer valve spring, which because of its rubbing contact on the inner surface of the coils, produces a friction-dampening effect on valve spring surge (harmonics). Wherever possible, lskenderian Valve Springs incorporate this damper coil.
VALVE TRAIN: The components or train of parts used to operate the valves in conjunction with the camshaft.
VASCO JET 1000: The Chrome-Vanadium alloy steel used in the sky Vasco Jet 1000 racing valve springs which virtually eliminates the fatigue problem encountered with ordinary valve springs.
VINCO CAMSHAFT INSPECTION OPTICAL DIVIDING HEAD: The world's most accurate dividing head -- accurate to ±1 second of arc (1!3600 part of 1 degree) and .000015 115 millionths of an inch). This machine is used to inspect all