Iron Duke engine

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Iron Duke
Overview
Manufacturer GM
Production 1977-1993
Combustion chamber
Displacement 150.8 cu in (2.5 L)
Cylinder bore 4 in (101.6 mm)
Piston stroke 3 in (76.2 mm)
Cylinder block alloy Iron
Cylinder head alloy Iron
Compression ratio 8.2:1 (1977-1983) 9.0:1 (1984+)
Combustion
Cooling system Watercooled
Output
Power output 85-110 hp (63-82 kW)
Specific power 0.56 hp/cu in (25.2 kW/L)
Torque output 123-135 lb·ft (167-183 N·m)
Chronology
Predecessor GM 2300 engine
Successor GM 122 engine

The Iron Duke Pontiac engine VIN code A (also called the 2500, 151, Pontiac 2.5, and Tech IV, though the decal on the air filter assemblies actually reads "4 Tech") was a 2.5 L (150.8 cu in) I4 piston engine. Early versions shared pistons and rods with the Pontiac 301 V8 since it was half a 301. All Iron Dukes were built by Pontiac beginning in 1977 and ending in 1993. After this time, the GM 2.2 L OHV 4-cylinder replaced it across the entire lineup of vehicles that offered it. This engine is not to be confused with the Chevrolet 153. Early Iron Dukes had a Chevrolet V8 bellhousing (also shared with its third generation inline six) instead of the Buick-Oldsmobile-Pontiac bellhousing bolt pattern until the early 1980s when the later versions were installed in FWD applications where the 2.8L bellhousing bolt pattern was phased in. Cylinder head design had the intake manifold mounted on the passenger side, and the exhaust manifold on the driver side.

This 151 was also used by American Motors (AMC) starting in 1980, as the base engine option in the RWD Spirit and Concord, and continuing in both cars through 1982. The AWD (4x4) Eagle carried the 151 as standard equipment for 1981, and carried it midway through the 1983 model year. It was also available (as the Hurricane) in economy model Jeep CJs. AMC replaced the Iron Duke 2.5L I4 with a 150cid Inline-4 derived from their own six.

Applications:

Year hp (kW) lb·ft (N·m)
1978 85 (63) 123 (167)
1979 90 (67) 128 (173)
1980 86 (64) 128 (173)

LS6[edit]

The LS6 was a 151 cu in (2.5 L) I4 engine produced from 1978 to 1979.

LS8[edit]

The LS8 was a 151 cu in (2.5 L) I4 engine produced for 1979.

LX6[edit]

The LX6 was a 151 cu in (2.5 L) I4 engine produced from 1977 to 1978.

LX8[edit]

The LX8 was a 151 cu in (2.5 L) I4 engine produced from 1979 to 1980. cross-flow head introduced(1)

151 and 151-S[edit]

These engines were 151 cu in (2.5 L) I4 (82-98 hp) engines produced from 1974 to 1992 for Chevrolet Opala (Brazil). They used only the conventional (not crossflow) cylinder heads from the earlier North American models, like the Chevy Novas'.

Crossflow[edit]

Cross-flow cylinder heads were added in mid-1979, leading people to refer to this version as the crossflow. Output stood at 90 hp (67 kW).

Tech IV[edit]

Tech 4
2.5l tech 4 engine.jpg
Overview
Manufacturer GM
Also called Iron Duke

GM Engine Tech4.png

Iron Dukes were fitted with fuel injection (TBI, via a single injector in the throttle body) in 1982. This version was christened the Tech IV, though Car and Driver later ridiculed it as the low-Tech IV. Power output remained at 90 hp (67 kW).

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 (73 kW).

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 5500rpm, and achieved 110 hp (82 kW).

The Tech IV uses the same bellhousing pattern as the 2.8 L 60-Degree V6.

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 camshaft gear that meshes directly with a steel gear on the crankshaft (no timing chain), a design also used by the Chevrolet inline six. 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. One upgrade is the use of the aluminum camshaft timing gear from a Chevrolet 250 inline six with the Iron Duke's crankshaft timing gear.

A few Tech IV owners experienced 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[edit]

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's Touring Car series. The Super Duty 4 (usually called the "SD4") is still in use today for ARCA Racing.

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 also produced a 16-valve head (Cosworth Project DBA, 1987) for the Iron Duke.[1]

See also[edit]

References[edit]

  1. ^ "Cosworth Type Reference". Race-cars.com. Retrieved 2012-06-04. 

(1)1979 chevy Monza Brochure

This link will show you that there isn't any parts interchange with the Pontiac 151 and the Chevy 153. http://www.rockauto.com/catalog/raframecatalog.php

External links[edit]