Engine Build Date Code

[Busted Knuckles]

Hagar-It is not a CA Jeep. I had it shipped here from Arkansas. It is a 49 State model. The Jeep is definately an 81, verified by all the VIN plates. Here is the tag on the carb (1DM2J):


And IO, here is the tag on the valve cover. Doesn't look mis-stamped


So what do you guys think?

Novemeber 11, 1980, 304.

This would not at all be unusual to find in a 1981 model year,.. Id call it most likely the original motor, unless someone randomly found another 80/81 motor to put it in. Im referecing the Factory Parts Manual section on identifiying engines...

 

[chodette]

So Busted, you think the "0" might stand for 80? Why would the TSM be wrong?

Anyone else out there with a 80/81 304? I would be interested to know what theirs was stamped.

 

[hagar]

Carb tag # 1DM2J = 1981 CJ 304 Manual trans except Calif.

based on the carb tag, I'd say it's an 81 model.

 

[Busted Knuckles]

So Busted, you think the "0" might stand for 80? Why would the TSM be wrong?

Anyone else out there with a 80/81 304? I would be interested to know what theirs was stamped.

Yes, there is no real "question here", production of vehicles has always started in the fall of the previous model year, and the motors have always been made at a different plant, and the dates will never match to the "day" the vehicle was built. So it perfectly common to see a late 80 engine in an 81. It would have all the 81 emissions controls on it, and considered an 81, but it the factories way of keep track of things, so they know if a motor has an newer or older style this or that. Its common in the parts manual to have a break point within a model year, that's why its dated.

The parts book will say, "all motors built after 1/31/80... as an example. Doesnt really always go my the "model year" alone, but in the case of aftermarket parts, the engine would be a 1981.

So order all your parts for an 1981.

Id call it a typo in your TSM. BTW, what TSM are you using ? Ive got the 81 TSM and it shows 5 for 1980, but the factory parts manual does not...

 

[chodette]

Thank you guys SO much!!! I have the 1981 Jeep TSM and it showed 5. That is where I was confused

This forum is so helpful

 

[Busted Knuckles]

I pulled that info out of the 74-80 parts catalog, the 81-86 follows suit with 1-1981, 2-1982 and so forth, which also does not agree with the 81 TSM.

Id believe the parts manual before the TSM. The parts manuals are usually updated every quarter for about 10 years, so they are typically correct, the service manuals get little if any updates/corrections. I wouldnt worry too much about it...

 

[Saddle Tramp]

Oddly enough the AMC engine plant coded the motors on a calendar year, not a model year; this is why the motor code year and the model year may be off. It would be expected to take a little time for the motor to make it to the line for installation after assemble in the engine plant. In your case:
0 = 1980 Build Year
11 = Month of the year, November
H = Displacement & Carb Type, 304 with a 2 BBL Carb
11 = Day of the month, assembled on the 11-November-1980.