GM Iron Duke Engine
   HOME

TheInfoList



OR:

The Iron Duke engine (also called 151, 2500, Pontiac 2.5, and Tech IV) is a
Straight-4 A straight-four engine (also called an inline-four) is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft. The vast majority of automotive four-cylinder engines use a straight-four layout (with the ...
piston engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
built by the Pontiac Motor Division of
General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
from 1977 to 1993. Thereafter GM's 2.2 L
OHV An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located bel ...
4-cylinder replaced it across the entire lineup of vehicles that offered it. Although its original purpose was to serve as Pontiac's new
economy car Economy car is a term mostly used in the United States for cars designed for low-cost purchase and operation. Typical economy cars are small (compact or subcompact), lightweight, and inexpensive to both produce and purchase. Stringent design const ...
engine, it was later adapted for use in a wide variety of applications across GM's lineup in the 1980s.


Development

At the time of the
1973 oil crisis The 1973 oil crisis or first oil crisis began in October 1973 when the members of the Organization of Arab Petroleum Exporting Countries (OAPEC), led by Saudi Arabia, proclaimed an oil embargo. The embargo was targeted at nations that had supp ...
the only engines Pontiac built were , , and versions of their V8 engine. Recognizing that future products would need to be smaller and more fuel-efficient, Pontiac engineers were tasked with developing a new engine that would be suitable for these future products. The engineers considered developing smaller displacement versions of the existing V8, a V6 derived from the V8, a V4 derived from the V8, and an inline-four derived from one of the
cylinder bank The engine configuration describes the fundamental operating principles by which internal combustion engines are categorized. Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categorize ...
s of the V8 (in the same fashion the 1961 Pontiac Tempest's "Trophy 4" engine), but ultimately decided to create an entirely new four-cylinder engine. The development team's design goals were to minimize noise and vibration while maximizing durability, drivability, fuel economy, and "usable" power at lower engine speeds. They began by analyzing other four-cylinder engines in production at General Motors at the time, and they found that
GM do Brasil General Motors do Brasil is the largest subsidiary of General Motors in South America, one of the oldest and largest car producers in Brazil. Founded in 1925 and initially located in the historic district of Ipiranga, São Paulo, the company a ...
's version of the Chevrolet 153 cu in four-cylinder—with a shorter
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
and longer
connecting rod A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksh ...
s—had significantly reduced secondary vibration as compared to the original Chevrolet design and the newer 2.3 L four-cylinder from the
Chevrolet Vega The Chevrolet Vega is a subcompact automobile that was manufactured and marketed by GM's Chevrolet subdivision from 1970 to 1977. Available in two-door hatchback, notchback, wagon, and sedan delivery body styles, all models were powered by an ...
. This obviated the need for counter-rotating balance shafts, which would have increased the weight, complexity and cost of the engine. Despite sharing the same bore, stroke and cylinder spacing as the Brazilian engine, the majority of parts are not interchangeable. Focusing on making power at lower engine speeds was a deliberate consideration in order to meet the rest of the design goals. Careful consideration was made to the design of the
intake manifold In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/ air mixture to the cylinders. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the ...
and
exhaust gas recirculation In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide () emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust ...
system to ensure power output from each cylinder was equalized. Power consumption of the water and oil pumps were reduced, and the
piston ring A piston ring is a metallic split ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine. The main functions of piston rings in engines are: # Sealing the combustion chamber so that there is min ...
s, cylinder bores and crankshaft journals were designed to minimize friction. To maximize durability the
engine block In an internal combustion engine, the engine block is the structure which contains the cylinders and other components. In an early automotive engine, the engine block consisted of just the cylinder block, to which a separate crankcase was atta ...
was made of cast iron with five
main bearing Main may refer to: Geography * Main River (disambiguation) **Most commonly the Main (river) in Germany * Main, Iran, a village in Fars Province *"Spanish Main", the Caribbean coasts of mainland Spanish territories in the 16th and 17th centuries ...
s, rather than the relatively fragile cast aluminum block used by the 2.3 L Vega engine. (Even with the cast iron block the Iron Duke only weighed about 20 pounds more.) The 2.3 L engine's belt-driven
overhead camshaft An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion c ...
was eschewed in favour of an overhead valve design with timing gears. Specially-designed bolts that stretch slightly farther than a conventional bolt were used to secure the intake and exhaust manifolds to the
cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...
, to allow slight movement while maintaining the seal of the gaskets in order to prevent cracking the manifolds as they expand with heat. A two-stage, two-barrel carburetor with electric choke was used to improve performance in cold starts, while heat shields incorporated underneath the carburetor and between the intake and exhaust manifolds were used to prevent heat soaking the gasoline in the carburetor thereby improving performance in hot weather. Recognizing that cars with four-cylinder engines equipped with
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
tended to experience drivability issues in hot weather, other improvements were made including a cut-off switch that shut the compressor off at
wide open throttle Wide open throttle or wide-open throttle (WOT), also called full throttle, is the fully opened state of a throttle on an engine (internal combustion engine or steam engine). The term also, by extension, usually refers to the maximum-speed state o ...
and a delay incorporated into the air conditioning's circuitry to prevent the compressor from engaging on until twelve seconds after the engine was started.


Early applications

The Iron Duke's first applications were in the 1977 Astre and
Sunbird Sunbirds and spiderhunters make up the family Nectariniidae of passerine birds. They are small, slender passerines from the Old World, usually with downward-curved bills. Many are brightly coloured, often with iridescent feathers, particularly ...
subcompact cars, replacing the 2.3 L Vega engine, and in the compact
Phoenix Phoenix most often refers to: * Phoenix (mythology), a legendary bird from ancient Greek folklore * Phoenix, Arizona, a city in the United States Phoenix may also refer to: Mythology Greek mythological figures * Phoenix (son of Amyntor), a ...
. As these cars were originally designed for Chevrolet engines the Iron Duke also used the Chevrolet bell housing bolt pattern, instead of the Buick-Oldsmobile-Pontiac V8 pattern. The following year use of the engine expanded to the Sunbird's Chevrolet and
Oldsmobile Oldsmobile or formally the Oldsmobile Division of General Motors was a brand of American automobiles, produced for most of its existence by General Motors. Originally established as "Olds Motor Vehicle Company" by Ransom E. Olds in 1897, it produ ...
twins, the
Monza Monza (, ; lmo, label=Lombard language, Lombard, Monça, locally ; lat, Modoetia) is a city and ''comune'' on the River Lambro, a tributary of the Po River, Po in the Lombardy region of Italy, about north-northeast of Milan. It is the capit ...
and Starfire. For model year 1979 the engine was extensively redesigned. The original
reverse-flow cylinder head In engine technology, a reverse-flow or non-crossflow cylinder head is one that locates the intake and exhaust ports on the same side of the engine. The gases can be thought to enter the cylinder head and then change direction to exit the head. T ...
was replaced by a crossflow design, a new two-barrel carburetor called "Vara-Jet" was introduced, the
distributor A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
was relocated, and the size of the oil pan was reduced. The only parts carried over from the 1978 engines were the connecting rods. Peak power increased to 90 hp. For 1980 the Iron Duke engine was redesigned to be mounted transversely, to suit the new front-drive General Motors "X-body" cars. The bellhousing bolt pattern was revised to match that of the new 60° V6 engine. GM also began selling the engine to
American Motors Corporation American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 1954. At the time, it was the ...
(AMC) starting with 1980 model year. It was the base engine in
Spirit Spirit or spirits may refer to: Liquor and other volatile liquids * Spirits, a.k.a. liquor, distilled alcoholic drinks * Spirit or tincture, an extract of plant or animal material dissolved in ethanol * Volatile (especially flammable) liquids, ...
,
Concord Concord may refer to: Meaning "agreement" * Pact or treaty, frequently between nations (indicating a condition of harmony) * Harmony, in music * Agreement (linguistics), a change in the form of a word depending on grammatical features of other ...
, and
Eagle Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, just ...
automobiles, as well as in base-model Jeep CJs. The engines purchased by AMC continued to use the Chevrolet V8 bellhousing pattern. The four-cylinder engine was dropped from AMC rear-wheel drive models after 1982. During 1983, the all-wheel drive Eagle base engine switched from the Iron Duke to a new, AMC-developed four-cylinder. The 1983 Jeep CJs were the last with the Iron Duke as base engine. * 1981–1982
AMC Concord The AMC Concord is a compact car manufactured and marketed by the American Motors Corporation for model years 1978–1983. The Concord was essentially a revision of the AMC Hornet that was discontinued after 1977, but more luxurious, quieter, ...
* 1981–1983
AMC Eagle AMC may refer to: Film and television * AMC Theatres, an American movie theater chain * AMC Networks, an American entertainment company ** AMC (TV channel) ** AMC+, streaming service ** AMC Networks International, an entertainment company *** ...
* 1980–1982 AMC Spirit * 1980–1981
Buick Skylark The Buick Skylark is a passenger car formerly produced by Buick. The model was made in six production runs, during 46 years, over which the car's design varied dramatically due to changing technology, tastes, and new standards implemented over t ...
* 1980–1981
Chevrolet Citation The Chevrolet Citation is a range of compact cars that was produced by the Chevrolet division of General Motors. The first Chevrolet sold with front-wheel drive, a single generation of the Citation was sold from the 1980 to 1985 model years. The s ...
* 1978–1980
Chevrolet Monza The Chevrolet Monza is a subcompact automobile produced by Chevrolet for the 1975 through 1980 model years. The Monza is based on the Chevrolet Vega, sharing its wheelbase, width, and standard inline-four engine. The car was designed to accommoda ...
* 1980–1983 Jeep CJ * 1980–1981
Oldsmobile Omega The Oldsmobile Omega is a compact car manufactured and marketed from 1973-1984 by Oldsmobile, as the brand's most affordable, entry level vehicle — across three distinct generations. The first two generations of the Omega used rear-wheel ...
* 1978–1980
Oldsmobile Starfire The Oldsmobile Starfire is an automobile nameplate used by Oldsmobile, produced in three non-contiguous generations beginning in 1954. The Starfire nameplate made its debut as a convertible concept car in 1953 followed with the 1954–1956 Nine ...
* 1977
Pontiac Astre The Pontiac Astre is a Subcompact car, subcompact automobile that was marketed by Pontiac (automobile), Pontiac as a badge engineering, rebadged variant of the Chevrolet Vega. Initially marketed in Canada for model years 1973–1974, the Astre deb ...
* 1977–1981 Pontiac Phoenix * 1977–1980
Pontiac Sunbird The Pontiac Sunbird (also known as the Pontiac J2000 and Pontiac 2000) is a model line that was manufactured and marketed by Pontiac from the 1976 to the 1994 model years. Loosely deriving its name from the Pontiac Firebird, the Sunbird was intr ...


Tech IV

Iron Dukes were fitted with
fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All comp ...
(TBI, via a single injector in the throttle body) in 1982. This version was christened the Tech IV, though ''
Car and Driver ''Car and Driver'' (''CD'' or ''C/D'') is an American automotive enthusiast magazine. In 2006 its total circulation was 1.23 million. It is owned by Hearst Magazines, who purchased prior owner Hachette Filipacchi Media U.S. in 2011. It was f ...
'' later ridiculed it as the ''low''-Tech IV. Power output increased to . This was replaced by a swirl-port head with 9.0:1 (instead of 8.25:1) compression ratio in 1984 for a gain. Other additions for 1985 included roller lifters, improved bearings, and a new
crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...
. Several significant changes were made in 1987, which included: an improved cylinder head, intake manifold and
throttle-body fuel injection Manifold injection is a mixture formation system for internal combustion engines with external mixture formation. It is commonly used in engines with spark ignition that use petrol as fuel, such as the Otto engine, and the Wankel engine. In a mani ...
module, a more-modern serpentine belt with an automatic spring-loaded tensioner for the accessories, and a
Distributorless Ignition System A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
(DIS). This revision to the engine increased power to . In 1988, a balance shaft was added to smooth engine vibrations. Up to this point, the engine incorporated a 'dogbone' upper front engine mount secured to the cowling of the vehicle's hood latch, aiding in controlling the vibration. Further improvements in later years included new pistons, rods, crankshaft, and an in-pan oiling system. The most powerful variant of the Tech IV raised the rev limit to 5500 rpm, and achieved . The Tech IV uses the same
bellhousing Bell housing or bellhousing is a colloquial/slang term for the portion of the transmission that covers the flywheel and the clutch or torque converter of the transmission on vehicles powered by internal combustion engines. This housing is bolte ...
pattern as the 2.8 L '' 60-Degree'' V6. Over the years, the Tech IV engine has proved to be a reliable workhorse for owners when not pushed to its limits. All 1978-1990 Iron Duke engines used a
micarta Micarta is a brand name for composites of linen, canvas, paper, fiberglass, carbon fiber, or other fabric in a thermosetting plastic. It was originally used in electrical and decorative applications. Micarta was developed by George Westinghouse ...
camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...
gear that meshed directly with a steel gear on the crankshaft. 1991-92 VIN R and U engines used a timing chain instead. * 1982–1992
Buick Century Buick Century is the model name that was used by Buick for a line of upscale full-size cars from 1936 to 1942 and 1954 to 1958, as well as from 1973 to 2005 for mid-size cars. The first Buick Century debuted as the Series 60 then renamed in 19 ...
* 1982–1991
Buick Skylark The Buick Skylark is a passenger car formerly produced by Buick. The model was made in six production runs, during 46 years, over which the car's design varied dramatically due to changing technology, tastes, and new standards implemented over t ...
* 1985–1987 Buick Somerset/Somerset Regal * 1985–1990
Chevrolet Astro The Chevrolet Astro is a van that was manufactured and marketed by the Chevrolet division of American auto manufacturer General Motors from 1985 to 2005. Sold alongside the GMC Safari, the Astro was marketed in multiple configurations, in ...
Cargo Van * 1982–1985
Chevrolet Camaro The Chevrolet Camaro is a mid-size American automobile manufactured by Chevrolet, classified as a pony car. It first went on sale on September 29, 1966, for the 1967 model year and was designed to compete with the Ford Mustang. The Camaro ...
* 1982–1990
Chevrolet Celebrity The Chevrolet Celebrity is a mid-size automobile that was produced by the Chevrolet division of General Motors from the 1982 to 1990 model years. Replacing the Malibu, the Celebrity was initially slotted between the Citation and the Impala w ...
* 1990–1992
Chevrolet Lumina The Chevrolet Lumina is a mid-size car that was produced and marketed by the Chevrolet division of General Motors from 1989 until 2001. __TOC__ Background The first generation of the Lumina replaced the Chevrolet Celebrity and Chevrolet ...
* 1985–1993
Chevrolet S-10 The Chevrolet S-10 is a compact pickup truck that was produced by Chevrolet. It was the first domestically built compact pickup of the big three American automakers. When it was first introduced as a "quarter-ton pickup" in 1981 for the 1982 m ...
* 1985–1987
Chevrolet S-10 Blazer The Chevrolet (S-10) Blazer and its badge engineered GMC (S-15) Jimmy counterpart are compact/mid-size SUVs manufactured and marketed by Chevrolet and GMC from the 1983 through 2005 model years, over two generations – until the early 1990s a ...
* 1985–1987
GMC S-15 Jimmy GMC may refer to: Government India * Gandhinagar Municipal Corporation, in Gujarat * Gobichettipalayam Municipal Corporation, in Tamil Nadu * Guntur Municipal Corporation, in Andhra Pradesh * Guwahati Municipal Corporation, in Assam * Gwalior ...
* 1985–1993 GMC S-15 Sonoma * 1985–1990
GMC Safari The Chevrolet Astro is a van that was manufactured and marketed by the Chevrolet division of American auto manufacturer General Motors from 1985 to 2005. Sold alongside the GMC Safari, the Astro was marketed in multiple configurations, in ...
Cargo Van * 1987–1994
Grumman LLV The Grumman Long Life Vehicle (LLV) is an American light transport truck model, designed as a mail truck for the United States Postal Service, which is its primary user. It is also used by Canada Post. History The Grumman LLV was specifically ...
(
USPS The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or Postal Service, is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the ...
delivery vehicle) * 1985–1991
Oldsmobile Cutlass Calais The Oldsmobile Calais is a compact car that was manufactured and marketed by Oldsmobile from 1985 through 1991, superseding the Oldsmobile Omega and named after the city of Calais, France. Renamed the Cutlass Calais for 1988, and briefly availab ...
* 1982–1992
Oldsmobile Cutlass Ciera The Oldsmobile Cutlass Ciera is a mid-size car that was manufactured and marketed from the 1982 through 1996 model years by the Oldsmobile Division of General Motors. It shared the front-wheel drive A platform with the Buick Century, Pontiac 6 ...
* 1982–1991
Pontiac 6000 The Pontiac 6000 is a Mid-size automobile manufactured and marketed by Pontiac for model years 1982-1991 in 2-door coupe, 4-door sedan and 5-door wagon body styles – as one of four rebadged variants, including the Buick Century, Chevrolet Celebri ...
* 1984–1988
Pontiac Fiero The Pontiac Fiero is a mid-engine sports car manufactured and marketed by Pontiac (automobile), Pontiac for model years 1984-1988. Designed by George Milidrag and Hulki Aldikacti as a sports car, it was the first two-seater Pontiac (automobile) ...
* 1982–1985
Pontiac Firebird The Pontiac Firebird is an American automobile that was built and produced by Pontiac from the 1967 to 2002 model years. Designed as a pony car to compete with the Ford Mustang, it was introduced on February 23, 1967, five months after GM's Che ...
* 1985–1991
Pontiac Grand Am The Pontiac Grand Am is a mid-size car and later a compact car that was produced by Pontiac. The Grand Am had two separate three-year runs in the 1970s: from 1973 to 1975, and again from 1978 to 1980. It was based on the GM A platform. Productio ...


Super Duty

The Iron Duke block formed the basis of Pontiac's ''Super Duty'' four-cylinder racing engines of the 1980s, the last in a line of high-performance Pontiac Super Duty engines. The engines were featured in
NASCAR The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
's Charlotte/Daytona Dash Series, the
IMSA GT Championship IMSA GT was a sports car racing series organized by International Motor Sports Association. Races took place primarily in the United States, and occasionally in Canada. History The series was founded in 1969 by John and Peggy Bishop, and Bill ...
(in GTP and GTU class cars), and even in
American Power Boat Association The American Power Boat Association (APBA) is an American membership-owned corporation. In 1903, New York's Columbia Yacht Club had formulated a constitution for what ultimately became the APBA. It is the United States sanctioning authority for the ...
racing boats. Super Duty engines continued to be used in ARCA racing until well into the 2000s. In addition to parts matching the Iron Duke's stock 2.5 L displacement other crankshafts and their corresponding connecting rods were offered by Pontiac Motorsports, resulting in displacements ranging from 2.1 L to 3.2 L. A 2.7 L, Super Duty engine powered the 1984 Fiero Indy Pace Car to over during the race, but Super Duty engines were never available in factory-built GM vehicles. However, GM sold the Super-Duty-specific parts at authorized dealers; a hobbyist could order all of the parts required to convert their stock Iron Duke engine to a Super Duty version. Kansas Racing Products continued to make the engines in the early 21st century after buying rights to make them from GM.
Cosworth Cosworth is a British automotive engineering company founded in London in 1958, specialising in high-performance internal combustion engines, powertrain, and electronics for automobile racing (motorsport) and mainstream automotive industrie ...
also produced a 16-valve, double-overhead cam head for the 3.0 L version of the racing engine (
Cosworth Cosworth is a British automotive engineering company founded in London in 1958, specialising in high-performance internal combustion engines, powertrain, and electronics for automobile racing (motorsport) and mainstream automotive industrie ...
Project DBA, 1987).


See also

*
GM H platform The H Platform, or H-body, name has been used twice by General Motors. The 1970s H-body was an inexpensive rear-wheel drive compact automobile platform from the 1970s, used for the Chevrolet Vega and Monza and their Buick, Oldsmobile, and Pontiac ...
*
GM engines This list of GM engines encompasses all engines manufactured by General Motors and used in their cars. Divisions When General Motors was created in 1908, it started out with Buick and soon after acquired Oldsmobile, Cadillac and Oakland. There we ...


References

* 1979 chevy Monza Brochure


External links

{{commons category, General Motors Iron Duke engines
Jeep 151 information
Iron Duke Gasoline engines by model Straight-four engines