Engine Codes

I have a 1978 CJ 5 Renegade 258 single barrel Carb, the engine code is 404C03. I'm looking into a little of the history of the CJ thinking the engine had been rebuilt. When I looked at this article: AMC Engine codes -- ALL OF THEM
(By Frank Swygert, Publisher, "Ame
rican Independent Magazine" (AIM)

amc-engine-codes-street2mud-com-4a9e2.html

I believe my engine was actually swapped out. The engine code tells me according to this and if I'm right, I have a 1971 April 258 (did have a 2bbl, I have a 1bbl probably from 1978), 3rd of the month.

My questions are in the article the C isn't clear if the C is for 1971
"C- 258 2 bbl (4.2L, 76-89)" I guess it doesn't matter much but was just wondering if I truly have a 71? Is there more I should be looking at to conclude this? I don't even know at this point how much it really matters because it runs great, but my curiosity got the best of me. Would I be improving anything going to a 2bbl being that, that is what the engine would have had. IE Compression, HP, and Torque?

Any thoughts appreciated

 

A "C" engine is 1977 or newer. A 2V 258 did not exist in 1971. Check your 1978 TSM.

4 = 1980 (1978 would be 2)
04 = April
C = 2V 258 cid
03 = third day

The 2V would have been a Carter BBD as shown in your TSM. I know the CJ did not get the 2V in 1977, likely not in 1978 either if your Jeep is equipped with the Carter YF 1V. Only the full-size Jeep trucks and wagons with the 258.

You can convert to 2V if you want. The factory iron 2V 258 manifold used 1977-80 will bolt in to replace you 1V manifold. The later 258 manifolds will work too, but you'll need both the aluminum intake and matching iron exhaust. Adding a 2V by itself will give you a modest power boost.

 

Ok, didn’t follow chart out that makes a lot more sense! I still wish I had original, but it could tell me a company that builds engines more than likely built this one and not someone like me that wouldn’t really know. Just guessing of course!

TSM for 78 is my hand book and I knew if it was a 78 it would be a 2. The chart I looked at stops at 79. Never dawned on me to look for 80’s thanks Tim