in Spirit, Concord, and Eagle 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 discontinued from AMC's 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 1980 through 1983 Jeep CJs were also available with the Iron Duke as the base engine. 1981–1982 AMC Concord 1981–1983 AMC Eagle 1980–1982 AMC Spirit 1980–1981 Buick Skylark 1980–1981 Chevrolet Citation 1978–1980 Chevrolet Monza 1980–1983 Jeep CJ 1980–1981 Oldsmobile Omega 1978–1980 Oldsmobile Starfire 1977 Pontiac Astre 1977–1981 Pontiac Phoenix 1977–1980 Pontiac Sunbird 1977 Pontiac Ventura Tech IV 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 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. Several significant changes were made in 1987, which included: an improved cylinder head, intake manifold and throttle-body fuel 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 . 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 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 camshaft gear that meshed directly with a steel gear on the crankshaft. 1991-92 VIN R and U engines used a timing chain instead. The Grumman LLV (Long Life Vehicle) built from 1987 until 1994 for the United States Postal Service for use in mail delivery were initially powered by the Iron