Buick 225/231 V6 Casting Numbers, Internal Specs For Most Years and Notes

Compiled by Joel Vande Berg

I have added this article to my page as the article doesn’t seem to appear on the EarlyCj5.com website anymore. If you are the author, please reach out to me so I can give proper credit to your work. If I am wrong and the page is still available on EarlyCj5.com, let me know and I will link it there.

The remainder of this reference is written and compiled by Jamie Carter and maintained by the Early CJ-5 Page.

225 Intake casting numbers:

• 1 barrel : 1381552
• 2 barrel : 1378704

– there may be others…

---

225 V-6 engine id codes: Buick special 64-67 (1 and 2 bbl.)

• 1964 = KH [between branches of right exhaust manifold]
• 1965 = LH [engine number on the right front face of the crankcase, just below cylinder head]
• 1966 = MH [as ’65 above]
• 1967 = NH [as ’65 above]

…so the codes are either on the side or front of the block just under the cylinder head.

(I have heard rumors of a few engines produced in ’63).

All are listed as 9.0-1 comp. ratio.

The engine codes seem to indicate that the first letter is the engine year, while the second letter of the Buick engine code denotes the displacement + power output / configuration of a particular engine for that year.

01 Jul, 2010 – thanks to Todd McCreary for pointing out an error in the previous statement. The second letter is not the compression ratio as previously stated here. AS

The front of the engine is to the right, the block casting # is on the rear, the engine # is on the right bank.

Thanks to Joel Vanguard for the picture of V6 number locations

---

From “Service Manual Jeep Universal Series“;

“The engine code number shown in Fig A-4 is provided to identify the Dauntless V6-225 engine. The meaning of the coded letters and numbers that are stamped on the right front face of the crankcase, just below the rocker arm cover, between exhaust manifold ports, is given below:

Letter to designate market:

• M-Military
• E-Export
• D-Domestic

Letter to designate year Built:

• N-1967
• P-1968
• R-1969
• S-1970
• T-1971

Letter to designate Engine Compression Ratio:

• H-V6-225 9.0 to 1 C.R. (2bbl carb)
• Y-V6-225 9.0 to 1 Marine (Low Profile) (2 bbl carb)
• Z-V6-225 9.0 to1 Marine (High Profile) 2bbl carb
• K V6-225 7.6 to 1 (2bbl carb)
• L V6-225 7.4 to 1 (2bbl carb)

The next three numbers are then the day of the year noted in the second position.

---

In 1965, some Jeep V-6′s are listed as coded “KLH” (and maybe’64 or ’66 engines as well, still trying to research this).

Sometime ’71 to ’74 Buick bought the 225 V-6 back from AMC Jeep and rebored to 231 cu in. The engine stayed odd-fire until sometime in early or mid ’77, when the engine was changed to even-fire by revising the crank throws (and other modifications). The odd-fire V-6 was gone forever.

I have no info of Buick using the “new” V-6 in ’74; first use seems to be in the ’75 models. I haven’t seen any info that shows these engines in production for ’72, ’73, or ’74 (of any firing order or displacement). All Buick 231 block casting numbers from my info begin with the numbers 124, 125, 126, or 255.

There are after market intake manifolds available for the 225 V-6. Two are the Weiand four barrel intake part #7541 and the Offenhauser 360. Even-fire 231 intakes have been said to work if you use a ’78 or older intake gasket. Be advised that a four-barrel upgrade may cost some low-end horsepower. Engine parts are said to be available from Kenne-Bell and Kanter Auto Parts, among others. Information on both companies is available via the internet.

(last update feb-1-99). Information from various sources named and unnamed, some personal opinions are expressed. Not responsible for errors, as the weeding of the garden of knowledge to find the flower of truth is a never-ending quest.

jdc. & ahs.