[Rich Biebel]

Originally Posted by Hemi Moose

The Iron Duke (also called the 2500, 151, Pontiac 2.5, Cross Flow, 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. 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 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 of their own, derived from their evergreen sixes.
The Iron Duke is often confused with Chevrolet's Stovebolt-derived 153 from the 1960s Chevy II, but the engines are entirely different - the Iron Duke's intake manifold is on the passenger side, as opposed to the driver side.
Applications:

• 1977 Pontiac Astre
• 1977–1980 Pontiac Sunbird
• 1978–1980 Chevrolet Monza, Oldsmobile Starfire
• 1980–1982 AMC Concord
• 1980–1982 AMC Spirit
• 1980–1983 Jeep CJ
• 1980–1984 Oldsmobile Omega, Pontiac Phoenix
• 1980–1985 Buick Skylark, Chevrolet Citation
• 1981–1983 AMC Eagle
• 1982–1986 Chevrolet Camaro, Pontiac Firebird
• 1982–1989 Chevrolet Celebrity
• 1982–1991 Pontiac 6000
• 1982–1992 Buick Century, Oldsmobile Cutlass Ciera
• 1984–1988 Pontiac Fiero
• 1985–1987 Chevrolet S-10 Blazer, GMC S-15 Jimmy
• 1985–1993 Chevrolet S-10, GMC S-15/Sonoma
• 1985–1990 Chevrolet Astro, GMC Safari
• 1985–1987 Buick Somerset
• 1985–1991 Pontiac Grand Am, Oldsmobile Cutlass Calais
• 1986–1991 Buick Skylark
• 1987–1994 Grumman LLV (USPS delivery vehicle)
• 1990–1992 Chevrolet Lumina

More written here...

https://en.wikipedia.org/wiki/GM_Iron_Duke_engine

This info is not correct if my memory is any good......The first year Pontiac engines had both intake and exhaust manifolds on the same side of the engine.....drivers side.
The following year the new and improved cross flow head was on that engine. Thats how I recall it and I worked in a Pontiac dealer and worked on those cars regularly.
GM was producing some real junk and as a line mechanic I got to work on all sorts of engineering marvels......

This was the era of "corporate engines under the hood". Engines were calibrated so lean they could barely get out the driveway sometimes without bucking and missing......and my personal favorite....the odd fire Buick V6 3.8....shook so bad they had to add counterweights and soft engine and trans mounts.

I have some very funny stories from my days working on these cars and what we did to try and diagnose and fix some of these cars.

It was a Pontiac-Jeep-Subaru dealership and I worked on them all as an A Tech....