GM Iron Duke engine

Iron Dukes were fitted with fuel injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....

 (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
Car and Driver is an American automotive enthusiast magazine. Its total circulation is 1.31 million. It is owned by Hearst Magazines, who purchased prior owner Hachette Filipacchi Media U.S. in 2011...

later ridiculed it as the low-Tech IV. Power output remained at 90 hp.

This was replaced by a swirl-port head with 9.0:1 (instead of 8.2:1) compression ratio in 1984 for a 2 hp (1.5 kW) gain. Other additions for 1985 included roller lifters, improved bearings, and a new crankshaft.

Several significant changes were made in 1987. These included an improved cylinder head, intake manifold and throttle body injection module, a more-modern serpentine belt with an automatic spring-loaded tensioner for the accessories, and a distributorless ignition system (DIS). This revision to the engine increased power to 98 hp. In 1988, a balance shaft
Balance shaft
In piston engine engineering, a balance shaft is an eccentric weighted shaft which offsets vibrations in engine designs that are not inherently balanced...

 was added to smooth engine vibrations. 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 5500rpm, and achieved 110 hp.

The Tech IV uses the same bellhousing pattern as the 2.8 L 60-Degree
GM 60-Degree V6 engine
The General Motors 60° V6 family of engines began with the 1980 Chevrolet 2.8 L V6 and continues to be produced today . Its use in the X-body cars leads some to refer to it as the X engine.It is a 60° vee block with pushrod heads, except for a single DOHC member, the LQ1...


Over the years, the Tech IV engine has proved to be a reliable, if noisy, workhorse for owners when not pushed to its limits. All 1978-1990 Iron Duke L-4's are outfitted with a micarta
Micarta is a trademark of Norplex-Micarta industrial high pressure laminates and refers to a composite of linen, canvas, paper, fiberglass, carbon fiber or other fabric in a thermosetting plastic, originally used in electrical and decorative Koekjes applications. Micarta was developed by George...

 camshaft gear that meshes directly with a steel gear on the crankshaft (no timing chain). 1991-92 VIN R and U engines received a timing chain. The timing gear has a tendency to crumble a tooth anytime after 80,000 miles. The cam gear simply shears a tooth at startup and the engine won't start; because of the non-interference design of the engine, no further damage occurs. When the cam gear loses a tooth, the camshaft AND distributor stop rotating during engine cranking. Replacing the gear requires heating the new gear in hot oil and quickly installing it for a press fit on the cam stub.

A few Tech IV owners experience minor driveability issues with the engine. There are several cheap/easy repairs that the shadetree mechanic can perform to keep this engine running at its best.

Inspection (and replacement, if necessary) of the MAP sensor, and its accompanying vacuum hose, is often a solution to many driveability problems. This sensor largely controls the engine's driveability. Stuck EGR valves are also very common on the Tech IV.

Racing versions

Though not a production engine, the Super Duty 4 racing engine was notable and widely publicized at the time. It was the basis for NASCAR
The National Association for Stock Car Auto Racing is a family-owned and -operated business venture that sanctions and governs multiple auto racing sports events. It was founded by Bill France Sr. in 1947–48. As of 2009, the CEO for the company is Brian France, grandson of the late Bill France Sr...

's Touring Car series. The Super Duty 4 (usually called the "SD4") is still in use today for ARCA
Automobile Racing Club of America
Automobile Racing Club of America is an auto racing sanctioning body in the United States, founded in 1953 by John Marcum. The current president of ARCA is Ron Drager. The ARCA RE/MAX Series races stock cars similar to those seen in past years in the NASCAR Sprint Cup Series, and indeed most cars...


A 2.7L 232 hp (173 kW) SD4 engine powered the 1984 Fiero Indy Pace Car to over 138 mph during the race. The SD4 was never available in production vehicles, however Pontiac's Performance Parts counter had all the SD4 parts available and one could garner a 2.7L 272 hp (203 kW) version and a 3.2L 330 hp (250 kW) version. All 2000 Indy Fiero replicas came with the 2.5L 92 hp (69 kW) Iron Duke engine.

The SD4 was the last in a line of high performance Pontiac "Super Duty" engines. Kansas Racing Products still makes the engines after buying the rights to make them from GM.

Cosworth is a high performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing , mainstream automotive and defence industries...

 also produced a 16-valve
In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and can operate at higher revolutions per minute than a two-valve engine, delivering more power.- Multi-valve rationale :A multi-valve design...

 head (Cosworth
Cosworth is a high performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing , mainstream automotive and defence industries...

 Project DBA, 1987) for the Iron Duke.

External links

  • Chevrolet Opala information
    Chevrolet Opala
    The Chevrolet Opala was a mid-size car sold by General Motors do Brasil from 1969 to 1992. It was derived from the German Opel Rekord and Commodore, but used GM USA sourced engines, two four-cylinder engines: the Chevrolet 153 4-cylinder from Chevy II/Nova which later got a new crankshaft and...

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