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Table of contents

1.1 "Dauntless" Buick 225
1.2 Buick 231
1.3 Buick 252


Buick 231 in a CJ-2A

Consider the Buick V6, it is short, plentiful, and powerful. What more can you ask for in your short Jeep. The Buick is well suited for a swap into any short CJ-5, CJ-3B, CJ-3A, CJ-2A, or their military brethren. It isn't so powerful you'll rip your frame apart and break your axles and it is spunkier than the F-Head and L-Head engines. It is also easy to buy and buy parts for.


"Dauntless" Buick 225

From 1966 until 1971 Jeep used the Buick 225 V6 as the optional engine in CJs. Kaiser purchased the tooling to build the engine from Buick in 1967 and began production of the engine. The "Dauntless" 225 is an "odd fire" engine meaning the cylinders fire odd order. The odd-fire design cause a the engine to idle a bit rough. This version of the engine and parts from these Jeeps can be used to swap a Buick V6 into your Jeep.

One big advantage of the Dauntless 225 V6 is the heavy flywheels used on these engines. The flywheels come in 75lbs and 100lbs versions to create low end torque. The normal car flywheels are closer to 45lbs.

The bid disadvantage of the 225 is it is more difficult to fuel inject because of the odd fire ignition. The tachometer signal will confuse the computer of regular TBI fuel injection.


Buick 231

When AMC purchased Jeep, they started putting AMC engines in Jeeps. The Buick V6 was not used after 1971 and with the gas crisis, Buick became interested in the V6 engine again. They purchased the tooling back from Jeep in 1974 and reworked the engine so it use components from the Buick 350 engine. The larger bore increased the displacement to 231 cubic inches.

In mid 1977, Buick introduced the first "even fire" version of the Buick V6. This engine has a smoother idle, but more vibration than the older engine. The odd fire engine uses a distributor cap with equal spaces between the plugs on the distributor cap and the even fire engine has unequal spaces between the plugs on the distributor cap. It is not very intuitive, but that's the way it is.

The 231s are internally balanced and the 225s are externally balanced. Technically, you need to rebalance a 231 if you replace the flywheel or install a flywheel in place of a flex plate. Some people report that they have had no problem swapping different flywheels on these later engines with out rebalancing.

Later Buick 231s use multiport fuel injection. The Buick V6s never used TBI fuel injection from the factory.


Buick 252

During the early 80s some large rear wheel drive cars used a version of the 231 with a bigger bore. The displacement of the 231 was pushed up from 3.8L to 4.1L or 252 cubic inches. This engine has the same external dimensions as the 231 and can be told from the 231 by the 4.1L cast in the drivers side rear instead of 3.8L. Keeping these engines cool is a bit more challenging than the 3.8L, but it is nice to have the extra displacement.


Swap Stories

Project Pieces & Parts Engine Installation: Project Pieces & Parts finally gets the fired up with a Buick 231 V6 sitting on engine mounts from Advanced Adapters

Corvette Starters: The Corvette used a nice Denso high torque and light weight starter. This is a great and relatively cheap way to upgrade the starter in your Jeep with Chevy or Buick engine.



Buick 225 V6The "Dauntless" 225 V6 engine was used in CJ-5s, CJ-6s, and Jeepster/Commandos.


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