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Main >> Engine >> Factory >> GM 151 I4

From JeepTech and JeepTech Publishing LLC, the Jeep knowledge base.

All text is available under the terms of the GNU Free Documentation License.


The GM 151 I4 engine.

The 151 (2.5L) inline 4 engine was used in '80-'83 CJs including the CJ-8, CJ-7, and CJ-5. The 151 is often called the "Iron Duke", but is actually a Pontiac engine designed to replace the Chevy "Iron Duke" I4 engine. The engine does have the Chevy bell housing bolt pattern though. The engine is manufactured by GM and uses a cast iron block and cylinder head with hydraulic lifters and 5 main bearings. The 151 certainly is not a screamer, the AMC I4 has much better HP and torque ratings.

The neat part about the engine is it has the same bell housing bolt pattern as a Chevy small block. The bell housing makes a great low buck Jeep to Chevy adapter since it is basically Jeep on the transmission side and Chevy on the engine side. A regular Chevy bell housing will bolt to the 151, so if you plan a transmission swap, a Chevy transmission would be the way to go. Also, a Chevy 305 or 350 will bolt right to the Iron duke bell housing. The down side of dropping in a V8 is most transmissions used with the Iron Duke are light weight units.

The GM 151 has the intake and exhaust manifolds on opposite sides of the cylinder head, but the AMC 150 has the intake and exhaust manifolds on the same side of the cylinder head. The picture at the top of the page is the passenger side with the intake manifold and carb. The drivers side is pictured below with the exhaust manifold removed.



GM 151
Bore x Stroke 4.00" x 3.00"
Displacement 151 ci(2.5L)
Compression Ratio 8.2:1
Horsepower (net) 82@4000
Torque (net) 125@2600
Main Bearings 5
Valve Configuration OHV
Fuel Rochester staged 2bbl



Thanks to David Ewing for the manifold identification tip. Thanks to Ed Lowe for keeping my GM engine history straight.



Additional Photos

The GM 151 I4 engine.



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