I have always thought and was told when I bought my 1978 CJ7 that it had a 258 in it. But I am questioning that right now mainly because the Jeep is about 28 years old and I have only had it for about 4-5 years. Who knows what happened before I got my hands on it or how it came from the factory. Since the 232 and the 258 look identical can anyone tell me were the engine numbers are located on the block so I can research and be sure which engine I have? Thanks <img src="/forums/images/graemlins/confused.gif" alt="" />

Burtv I think the carbs would tell you... I think the little engine had a one venturi and the 258 has the 2 venturi..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

At that time the 258 came with 1v or optional 2v. But the question really is what happened or may have heppened with this jeep the 20+ years before I got it. Do you know where the block casting numbers are located?

The engine code is stamped on a smooth flat boss on the block just ahead of the distributor. The first digit indicates the year, 1978 would be represented by a 2. the next two digits are the month, then the engine type, a 258 from that time period would be a C, a 232 would be a E or with certain engines a F. the last two digits are the day the engine was built.
IE: 210C12 would be a 258 built on Oct.12th 1978.
After 1980 the first digit matches the last digit of the year so 210C12 could also be on a 1982 engine.

AMC engine date codes are explained HERE . <img src="/forums/images/graemlins/cheers.gif" alt="" />

Outstanding information, this is why 4x4xWire.com is one of the best sources of Jeep and Offroad information shared on the internet.
The number on my engine is "305C10". So based on this new information the engine in my 1978 Jeep is a 1983 258 manufactured on May 10 1983 and should of had a 2v carb. But when I bought the Jeep it had a 1v carb. This proved my suspicion that things may have changed in the 20 plus year period. WOW <img src="/forums/images/graemlins/kewl.gif" alt="" />
Thanks again you guys!!!!!!

"305C10" could also be 1979. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Well this is critical information you have let alone confusing and not very reliable (the coding that is)I thought there should be a seriel number also. If it is a 1979 then it has 1/2 inch head bolts and the 1983 has 7/16 head bolts at least by my research. So if I did a 4.0 head conversion and have a 1983 the block may have to be drilled out to 1/2 inch. This all of course is subject to a compression check of the engine before doing th conversion. I think I should have at least 125 lbs in each cylinder.
As per this link- http://www.off-road.com/jeep/tech/engine/amc258.html

Do you know of anyway to determine which year engine it is, short of pulling a head bolt or valve cover or???

It probably is a 79. There was a change in the head and valve cover, the stock 79 valve cover was steel and the stock 83 valve cover was plastic. Heads get swapped but if it has a steel valve cover it's most likely a 79. Also, you can use the 7/16 bolts (if you have them) no problem with a 4.0 head. I bought some spacer/washers for mine, the 4.2 head I replaced had 1/2" holes and no spacers and worked fine with 7/16 bolts also. Two spacers would insure the head is where it needs to be, the head bolts don't care if there is a little space around them. You can redrill the block and use 1/2" bolts but it is a waste of time and money IMO. <img src="/forums/images/graemlins/cheers.gif" alt="" />

It has an after market valve cover on it. Clifford I think? When you did your 4.0 head conversion did you rebuild the entire engine at the same time? Do you agree that if I get at least 125 lbs of compression on each cylinder that it should be good to go for the head swap? How much variance in compression from one cylinder to another is acceptable? I intend to add the Mopar MPI system also.

My engine had been previously rebuilt. An engine can be worn out and still have good compression and a good engine with leaking valves can have bad compression. 125 sounds kinda low, I wouldn't be concerned about it if it were the low reading and there is not more than 15% difference between the lowest and highest reading. Oil pressure is a better indicator of the condition of the lower end. If you have good compression and good oil pressure, go for it! If the engine needs work later your head and Fuel system will still be good, hopefully! <img src="/forums/images/graemlins/cheers.gif" alt="" />