Central Virginia Machine Service - Home of the Injun Engine!

    This is an attempt to clarify certain technical terms and acronyms used throughout the automotive engine industry, OEM and aftermarket. There will be some lengthy explanations, as one must understand certain fundementals in order to understand the more complex and evolved concepts.

    Good place to start, "OEM". Original Equipment Manufacturer. And the accompanying "aftermarket" refers to any and all suppliers of parts and service for cars (or anything, really) not originally installed on factory produced cars, as they supply performance parts and appearance enhancements not available on the "as delivered" factory cars.

    Machinist's terms are of the utmost importance in order to be able to communicate with a technician. Some are technically correct, particularly nomenclature, or "the correct name of a component". Others are vernacular of the engine building industry. We will assume the reader is familiar with the basic concepts of the 4-stroke cycle engine, and is also familiar with the main components, such as crankshaft, cylinder head, etc. A good grasp of basic algebra and geometry is a plus. We will also assume the tools and machines described in these terms will be in good operating condition and the operator is trained and experienced. Use of worn out tools and wobbly machines will lead to disaster.

Balance	"Balancing" an engine is a machine process by which all the parts in the rotating mass have their weight matched and the appropriate modifications made to the crankshaft to accommodate those weights through a certain RPM range. The "rotating mass" consists of the crankshaft and any and all parts attached to the crankshaft. Those are the rod, piston, piston pin, rings, rod bearing, harmonic balancer, flywheel or flex plate, torque converter or clutch and pulleys. To balance an engine, all the parts must be weighed. The lightest piston is found. The other pistons in the set have a slight amount of material removed to make them match the "light" one. The rods are weighed at each end, and for overall "static" weight. One set of rings, one piston pin, one rod bearing (both halves) and a slight amount of (about 4 gm.) oil in the crankshaft passages are also weighed. There are the reciprocating parts and the rotating parts. Engine families have their own specifications. Most American V8s (including the Pontiac) use similar balancing specs. Those are 100% of the rotating weight and 50% of the reciprocating weight. The piston, pin, rings and "small end" of the rod make up the reciprocating weight. The "big end" of the rod, rod bearing and oil make up the rotating weight. From these calculations, "bob weights" are made up consisting of twice the total weight of one set of parts. A bob weight is attached to each rod journal on the crankshaft. The crankshaft is mounted in a fixture that will spin it and measure the vibrations associated with centrifugal force and weight. Some machines use a strobe light system , but in today's modern shop, electronic sensors measure the vibrations. Material is either added to or removed from the counterweights of the crankshaft to minimize the vibration, enhancing performance and engine life, particularly the main bearings. It is exactly the same principle as balancing the tires on your car, with a just a little more precision.... SAE specifications for a new vehicles during the muscle car era, were to maintain a balance to within 1/2 of one percent of the entire rotating mass. With a large V8, this means the balance must be accurate to within about 35 grams. A modern shop will balance your performance engine to within 1 gram, and some have the capability to get it within 1/10th of a gram. Balancing even a stock rebuild is highly recommended.
Blueprint	Perhaps one of the most misunderstood and commonly abused terms in engine building is "blueprint". A true "blueprint" is the meticulous machining and part-matching to have the engine build arrive at exactly the specifications (and same tolerance adherence throughout) put forth on the engineering drawings or blueprints. In practice, due to the popularity of altering factory specs for performance changes, blueprinting is more making all the dimensions equal, rather than making them all a specific size. One example is rod bearing clearance. Stock specifications call for .0005-.0025" clearance. In a performance engine, .003-.0035" is more common. Some of the more common parameters addressed in a "blueprint" are the parallelism between the main bearing housing bore, cam bore and deck surfaces. The deck is also set to be perpendicular to the centerline of each cylinder bore. The rod journals are "indexed" to assure exactly 90 degree separation. Stroke is also more closely set during the crankshaft grinding process. Combustion chambers are all measured and equalized. The valve stem length is set to assure consistent cam timing to each cylinder. Valve spring installed height or "stack" is set to keep all springs within a tight range of tension. Piston- to-cylinder wall clearance is adjusted to be consistent. Ring gap is carefully set. Blueprinting is labor-intensive and therefore very expensive. It also requires a shop with high quality machines and operators skilled in the use. The machinist must know how to consistently measure a variety of parameters. Blueprinting is not generally a job for your parts house machine shop. For a racing engine destined for a specific class where engine modifications are limited and necessary to be competitive, blueprinting the entire engine is a must. Due to the expensive nature of the process, this is usually reserved for the professional level of racing, such as NASCAR Cup, Busch, NHRA classes, etc. For an engine destined for street machines or bracket racing, only partial blueprinting is necessary. Those parameters that most affect engine life are more important than those that affect power production This can explain the variations in price for an engine in a given family. A brakcet racing 350 Chevy can be built for less than $10,000, and will provide perhaps several seasons of racing at a high level where a Nextel Cup 355 can cost upwards of $45,000 and be used for one weekend! The main differences are the level of the blueprint and the quality of the parts. A bracket engine does not have the requirement of running against other engines of the same family, under the same rules regarding performance modifications. A bracket engine also lives above 6,000 RPM for a short time in each usage. The Cup engine must live above 7,500 RPM for extended periods of time and race against others using exactly the same equipment. The few horsepower gained through a thorough blueprint and the lack of wear from even power pulses and parasitic drag can make the difference between winning and losing a Cup race, where those same benefits will not be as apparent to a bracket racer that can merely adjust his/her driving to compensate for engine performance.
Bore	"Bore" or "boring" is the process by which a round hole ("bore" as previously described), the walls of a given hole are drilled or cut to a predetermined size. In the vernacular, to "bore" a block is to enlarge the cylinder to a specific oversize as compared to standard. There is more than one method that may accomplish this task without necessarily drilling or cutting.
Bore gauge	A "bore gauge" or "dial bore gauge" is a device that accurately measures the diameter of a given "bore". A "bore" is any drilled or honed hole, not limited to the "bore" of the cylinder, such as a lifter "bore", valve guide "bore", etc. The bore gauge will typically use three points to position a dial indicator in the center of a bore.
Crankcase	The "crankcase" is the internal area of the engine, below the valley where the crankshaft actually spins. While sometimes referred to as part of the crankcase, the area above the valley and in the valve covers is not technically "crankcase". Crankcase ventilation is a significant factor in both power production and engine life. Crankcase pressure can create serious oil leak issues.
Cut	"Cutting" is the process where a tool or set of tools is used to tear or peel material from the surface of a given part. The "cutter" is the tool piece that does the actual work. It is usually made from a hardened material and ground to a profile consistent with the desired finish quality of the "cut". Cutters may be mounted on a rotating wheel (broach) or in a tool post (lathe) or in a chuck (mill, horizontal or vertical). The mainstay of cutter material over the years has been "high speed steel", so named for the processes used to smelt it. In recent years, "carbide" (a very hard surface with good wear characteristics and tolerable level of brittleness compared to other materials of similar hardness), and is the material of choice for most machine tool cutters. They are higher priced but the finish quality and usable life make them worth it. What ever the purpose of the cutter, it must always be harder than the material it is designed to cut, for obvious reasons.
Deck	The "deck" is the surface of the block where the cylinder head is attached. It is also the name of the head surface that attaches to the deck of the block. To "deck" a block is to resurface the deck, either to simply renew the surface or to set the distance between the centerline of the crankshaft and the deck surface, or "deck height".
Degree wheel	A "degree wheel" is a circular plate, usually aluminum, accurately marked in degrees (360). The degree wheel is used for a number of operations involving the crankshaft or camshaft, and in accurately timing the camshaft/crankshaft relationship. Is also used to find "true" top dead-center or bottom dead-center of the stroke. Some degree wheels have only one degree graduations, where many made with automotive use in mind, have approximate ranges marked for cam timing events.
Dial caliper	A "dial caliper" is a measuring device using a sliding mechanism and two points (flat or pointed) to determine the size. Calipers are calibrated in either standard or metric graduations. They are also available these days in "digital" form, where the size measured is displayed by an LED or LCD. A dial caliper is considered accurate to within .001". The latter is much easier to read by the untrained eye.
Dial indicator	A "dial indicator" is a measuring device that uses a plunger to move a needle on a calibrated face (like a watch face), capable of measuring accurately to .0001". Most designs are fully adjustable and require setting by the user, rather than having a preset range like the micrometer. There are a variety of mounting devices and fixtures to make the dial indicator one of the most versatile of common measuring devices.
Engine	An engine is the mechanical device that produces power by burning a fuel and converting the heat energy released into motion. There are many different types of engines. The Pontiac is an "internal combustion, 4-stroke cycle gasoline engine".
Feeler blade	The "feeler blade" is a useful tool for measuring clearance between two parts. A feeler blade is not as accurate as the micrometer or dial indicator. It is very useful in areas where accuracy is not as stringent as that of other areas. A good example is valve lash with a mechanical tappet. Feeler blades are usually made of a high quality, hardened steel, and ground to a close-tolerance thickness. There are those also made for electrical uses that are made of non-magnetic brass. Size ranges are usually from .0015" to .035" or .040" . They are also available in metric sizes, but that is outside the range of this discussion.
Gallery	The oil "galleries" are the passages that run through the block, distributing the oil to the areas that require oil under pressure. Galley The "galley" is a kitchen aboard ship. This a commonly misused word for "gallery" as previously described. If you want to sound like John. Q. Customer or a shade tree mechanic, say "oil galley". If you want to sound like you may know a little something, and gain the attention of the machinist you're working with, say "oil gallery". There are no kitchens in an engine.
General	When common words are used to describe a condition or situation, the most literal definition of that word should be considered. One example is "straight". When a part is "straight", it is EXACTLY straight. When it is "flat", the surface is true and requires no resurfacing. Some of this is technically correct and other is vernacular.
Grind	"Grind" or "grinding" is a process where material is removed from a part through a turning stone or similar material. Grinding will remove material better from harder surfaces than "cutting" and will also yield a variety of surface textures, depending on requirements. Grinding can also yield a very flat, round or true surface, again, depending on the requirements.
Hone	To "hone" a bore is to use a grinding technique (grinding requires a stone or similar media) to enlarge the diameter or resurface the walls of a bore. Honing may be done either "dry" or "wet" Dry is to rotate the stone in the bore without lubrication. Wet is to use some method of lubrication. For heavy honing processes, wet honing is generally used, as it cools the process and carries away the residue from the grinding process. For parts that reciprocate in a bore, honing will leave the most desirable finish for long life. Honing will also leave the most accurate dimensionally "round" (a perfect circle) bore. The machine or device used in the honing process is also known as a "hone". The measuring skills of the hone operator will determine the accuracy of the finished product.
Micrometer	A "micrometer" is a precision measuring device capable of accurately measuring a component to within .0001" (one ten-thousandth of an inch) Micrometers are referred to as their range of size. Most "mics" cover a range of 1". One that measures from 1" to 2" is known as a "one to two mic". There are "inside" and "outside" mics, for measuring either the inside or outside dimension of of a given part.
Mill	"milling" is the process where material is removed from a part while the part is fastened securely on a milling "table". The cutter is mounted in the milling "head". Either the table or the head move in a manner that allows the cutter to remove material from the desired area at the desired speed and depth. In most cases (by no means, all), the table will move and the head will remain stationary. There are vertical (cutter is mounted up and down), horizontal (cutter mounted sideways) and "swing" mills. The "Bridgeport" mill is probably the best known. Made in Bridgeport, Connecticut, these vertical mills are the standard by which all vertical and horizontal milling machines are measured The swing mill is most used for surfacing or resurfacing large, flat parts. The Storm Vulcan 85B "BlockMaster" is an excellent example of a swing mill for automotive use. This machine is very large and rigid. It uses an "overhead" swing broach (the work lies under the cutter wheel as the head passes over). The swing is an arch as the cutter wheel traverses the surface of the part using a fulcrum at the rear of the machine. As the name would indicate, it is very good for resurfacing an engine block. In the vernacular, "milling" a head or block may or may not include the use of a milling machine, but does indicate the part has been resurfaced, regardless of the technique used to do it. "Planing", "shaving", "surfacing" and "grinding" are also vernacular for resurfacing a cylinder head.
Motor	In the vernacular, a "motor" is an engine. In truth, a motor is an electric device that converts electric energy into a rotating motion through the use of magnetic induction. In the engines business, we use the word "motor" often. It is technically incorrect, but very popular.
Port	The "port" is the passage in the head that the intake charge or exhaust gasses pass through on their way in or out. To "port" is to remove material from the entrance/exit of the port, or to enlarge the cross-sectional area of the port. Another term used to describe the port (usually the intake) is "runner".
Pushrod	The "pushrod" is the small diameter shaft that rides between the lifter and rocker arm, activating the appropriate valve by following the camshaft profile. It should not be confused with the connecting rod. If someone says they have a "blown rod", they're not referring to the pushrod, though there have been some confusing conversations where this was the case.
Ream	"Reaming" a hole is to drive a rotating cutter with a precision size and finish through it. The tool is a "ream" or "reamer". Reaming is a good prelude to honing, as with valve guides. In many processes of initial machining to a raw casting, reamers immediately follow drills. The drill will be small enough to allow the reamer to leave a precision finish over the entire wall of the bore or "hole". The drawback of a reamer compared to a hone is the reamer will follow any longitudinal imperfections (down the length) of a bore. A hone will force the centerline to as close to perfect as is possible. A reamer will maintain good dimensional integrity in the diameter. There are reamers of various types of material to do a quality job and give reasonable tool life for certain specific materials. A reamer for cast iron valve guides will have a different surface hardness and blade profile than one bronze guides.
Rod	The "rod" is the connecting rod. That's the long piece that connects the piston to the crankshaft. It commonly confused with the "pushrod".
Standard	When used describing equipment or design, "standard" is what ever came on a given car, as delivered from the factory . 3.55:1 axle ratio was "standard" with manual transmission GTOs When used describing a dimension (measurement), "standard" is the original dimension. A rod journal measuring 2.249" is "standard". There is also a calibration tool known as a "standard". An example is that for micrometers, where a hardened shaft is cut and ground to EXACTLY a specific length, inserted into a micrometer in order to determine the accuracy of that micrometer. One that is 1" long may be used to calibrate either a 0"-1" or 1"-2" mic.
Telescoping Gauge	A "telescope gauge" or "snap gauge" in the vernacular, expands in two directions and has a Gauge locking mechanism to accurately retain a certain length (any length covered by the gauge's range) to be measured by an outside mic. The snap gauge is useful in measuring bores in hard-to-reach areas. Also useful in repeating a specific dimension while sizing more than one part to the same specification.
Timing	There are two forms of "timing" in an engine. These are often an area of confusion. There is "cam timing" and "ignition timing". Cam timing describes the relationship between the valve events and the crankshaft or position of the piston, read in crankshaft degrees. Ignition timing is the point where the spark is thrown to the appropriate cylinder from the distributor, also read in crankshaft degrees. For the most part, the two are independent of each other.
Tunnel	There are two "tunnels" in a typical engine block. The cam tunnel and main bearing tunnel. These are the housing bores for the camshaft and crankshaft. Another name for the main bearing tunnel is the main "saddles", as that's where the main bearings ride in the block. The straightness and roundness of these tunnels is very important, and being parallel to each other is also extremely important. The centerlines of these tunnels must also be parallel to the deck surface of the block.
Valley	The "valley" of the block is the area above the camshaft, where the lifter bores are. This may be the single weakest point in a factory Pontiac block. Pontiac knew this, as the Super Duty blocks had additional ribbing in this area. The aftermarket Indian Adventures block has a "solid" valley, making it MUCH stronger in this area than any of the factory blocks.
Windage	"windage" is the term used to describe the action of the oil and air captured by the spinning crankshaft. Windage can also have significant effects on engine performance and oiling. The oil clinging to it, and the oil being churned into a vapor mixing with the air in the crankcase, will create a parasitic drag on the entire rotating mass.
Work	"Work" is any part, or piece of material destined to become a part, mounted in a machine for the purpose of using the machine to perform that particular operation. Work is also what we do all week so we can enjoy the hobby of building and driving old Pontiacs on the weekends!