Id's numbers

Just got a I6 trying to figure out if it's a 232 or 258 was told it's a 258. Just want to make sure before I buy parts .casting#3224098. block# 904co6.

904C06 is the "Engine Day Build Code"

9 = year - 67, 76, or 86. Code started with 1 for/in 1959, didn't use a zero, and repeated with 1 in 1968. In 1980 AMC started using zero and the last number of the year (0 = 1980, 1= 81, etc.), again repeating in 1990. So you have to know when a particular size was built (and sometimes features of a year) and some other info to decode the actual year.

04 = month -- 01 = January - 12 = December...

C = engine code letter.  60-67 code are different than 68 and later. 60-67 C = 195.6 OHV, and you know you don't have that! 68+ C is a 76-89 258/2V, so you have a 76 or 86 engine. If it has a stock cast iron intake and exhaust that bolt together under the carb it's a 76, if it has an aluminum intake and cast iron exhaust that don not bolt together it's an 86. Note that the manifolds could have been changed though.

06 = day of month, 01-31.

Finally, your block casting number. 3224098. That number was used 75-79, so it appears that you have a 76 engine. My list of casting numbers may not be complete or 100% accurate, but that's the best info I have for that number.

The head bolt size helps a little, but not much. 64-79 and 87+ AMC/Jeep sixes use 1/2" head bolts, 1980-86 use 7/16" (calendar year, not model year) . 80-86 also use a plastic valve cover, but many of those have been changed out to aftermarket stamped steel or cast aluminum covers.




Edited by farna - Nov/26/2017 at 9:17am

 Both engines share a 3.75" bore. If the heads are off check the stroke. The 232 is 3.50 and the 258 is 3.90.