Identifying your 4.2L engine

Ok, this is what I found out in case anyone is interested.
There are two main codes on a block that can help identify a 4.2L engine
1st. ENGINE DAY BUILD CODE. This is located on the passenger side of the
block just below and between #3 and #2 spark plugs holes. It's a flat plate
and has this format:
The Engine Day Build Code consists of six characters:
1. Year built code
2 & 3. Number of the month
4. Engine size/type code
5 & 6. Day built
Mine is 012C05
Which comes out to:
0=1980 or 1990
12=Dec
C=2v carb
05=day of the month built
See this site for more info:
formatting link

I was unclear on whether this would be a 1980 or 1990 engine. To narrow
it down I located the Engine Serial number (2nd main code) which is located
right behind the O2 Sensor on the Drivers side of the block.
Mine reads: EF3235444
When I looked for this number on remanufactured engine sites I see that
this block serial number started in 1981 through 1990.
Therefore the best determination I can make is this engine is a 1990 made
engine.
Hope this helps someone.
Bill
Reply to
William Oliveri
Umm... Bill yours is a 76-89 258 2bbl carb engine....
That is what the 'C' means.
The '0' means 1980.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's
Reply to
Mike Romain
You are the one that posted the freaking link Bill!
Did you not read it?
I did.
And no 'C' does 'not' stand for carb.
Mike
Reply to
Mike Romain
I stand corrected. C does not stand for carb and it does say the dates run to 89.
C- 258 2 bbl (4.2L, 76-89)
However, every site I've looked at similar to this one:
formatting link
says that the serial number of 3235444 started in 81, not 80 which is why it's confusing.
Go to this site
formatting link
and searchfor 3235444 and you'll see what I mean. Bill
Reply to
William Oliveri
They warned about that on the first link Bill.
Some of the numbers went on when it was made and some went on for the actual model year it was sold as or built for.
Here is a quote:
An important thing to remember about AMC engines is that changes were made on a calendar year basis, not model year. The engine plant ran on its own schedule! This is why some 1980 model vehicles have the "heavy" 258 and others the "light" 258 -- changes were made early in calendar year 1980.
Mike
Reply to
Mike Romain
Do you know what this means? Heavy 258 and Light 258?
What would really help is to totally exclude 1990 year engines. I need to find out what the date code stamp is for a 1990 258.
My situation is a little different. The previous owner had the short block replaced due to him pouring water on a over heated engine. I have all the receipts. He had the head serviced for over 1000.00 and replaced the short block with a used one for over 2000.00.
This was in 1997 on a 83 CJ7. If the shop replaced the short block with an 80 year block that would be very bad. Not to consider the smog logs require a newer or same year engine to be replaced.
I know I have 1/2" head bolts and not 7/16" but that doesn't help either because 80 and 90 year blocks have 1/2" head bolts.
Bill
Reply to
William Oliveri
You can't have a 90, the cranks are different and the transmission will not bolt up to it without some serious machining or searching for parts.
They changed to the YJ setup in 87.
They used 2 engine blocks for the 1980 year. You got the later one or the 444 cast.
That does not mean you got a 1980 'engine', just a block from that year. The crank could be any up to 86.
If this is a built up short block, then the engine cast just came out of a pile they had around the shop and they put a CJ crank in it.
All bets are off when talking built engines, nothing has to match up 'properly' and a block is basically a block.
Not likely the fool paid $2000.00 for a 'used' short block, that is a really expensive rebuilt one's price.
Emissions look at the heads and exterior junk.
Mike
Reply to
Mike Romain
Wow, Ok. Even though the receipts do not state "rebuild" but "replaced" with a used engine, I am hopeful you are correct.
Thanks Mike. That helps a lot.
Bill
Reply to
William Oliveri
One way to tell 'maybe' is by just looking close at the oil pan gasket or timing cover for RTV or gasket maker.
When someone installs a used engine, they don't mess with those covers usually. Your compression is also correct for a 'new' engine.
A used 258 short block goes for a couple hundred dollars, not a couple thousand....
Mike
Reply to
Mike Romain
There's no "short" version of the AMC 258.
A grand for the head, eh? I just looked at my checkbook: $187.09US to have my 258 head hot-tanked, the valves ground and new seals installed at a local speed shop. While it was there they made a pass through the planer just to be sure it wasn't warped and backed out a broken stud for me.
Two grand to have a shop R/R an engine doesn't surprise me, though.
It goes by smog system, not individual parts, no?
Reply to
Lee Ayrton
I have a 1990 258 (now with a Weber carb.). Is there anyway I can lookup some info. for you guys to solve this mystery?
Reply to
KJ
Yeah, that'd be great. Look on the passenger side of the engine just below the #3 and #2 spark plug holes on the block. There should be a flat plate there with some numbers and letters on it.
What does it say?
Thanks,
Bill
Reply to
William Oliveri
Correct me if I'm wrong but the term "short block" is referring to the engine without the head. "Long Block" would be referring to the engine with the head.
I'll scan the receipts in tomorrow up to my web page for reference. He also had the carb rebuilt by Chrysler which was also big bucks.
Reply to
William Oliveri
063CL06
1990 Jeep Wranger YJ w/ 258
So, 1990 year model w/ a 1986 block?
The C is close enough in stating that it is a "C- 258 2 bbl (4.2L, 76-89)", but the "L" baffles me.
Anyone have a clue as to the "L" portion of the designation? The website info. for the "L" doesn't make sense in this case.
When ordering parts, I usually tell the parts flunkies behind the counters it's an 1989....I'll normally get the parts right that way since if I tell them it's a 1990, they screw up more often.
Reply to
KJ
This number is in a different format than the web site states. Looks like the format changes in 1990 otherwise your number would be:
Year 1990 Month 63 Day Built 06
Doesn't fit the following format:
1. Year built code 2 & 3. Number of the month 4. Engine size/type code 5 & 6. Day built
However, this information does confirm Mike's position which is now very clear.
It could be that the day code letters are two letter codes rather than the single letter codes the CJs have but that's just guessing.
Bill
063CL06
1990 Jeep Wranger YJ w/ 258
So, 1990 year model w/ a 1986 block?
The C is close enough in stating that it is a "C- 258 2 bbl (4.2L, 76-89)", but the "L" baffles me.
Anyone have a clue as to the "L" portion of the designation? The website info. for the "L" doesn't make sense in this case.
When ordering parts, I usually tell the parts flunkies behind the counters it's an 1989....I'll normally get the parts right that way since if I tell them it's a 1990, they screw up more often.
Reply to
William Oliveri
bill-here's some more info about the engine- Oversize or undersize components look between the ignition coil and the distributor. there may be a couple of letters stamped on a boss. here are the codes:
B - All cylinder bores (0.254mm (0.010") oversize) M - All crankshaft main bearing journals (0.254mm (0.010") oversize) P - All connecting rod bearing journals (0.254mm (0.010") oversize) C - All camshaft bearing bores (0.254mm (0.010") oversize)
Example: if you see the letters "PM" you have crankshaft bearing journals and connecting rod journals that are undersize.
this info is out of my factory manual-if you can afford them ($100 in 1998), get a copy of it. it has sooo much info on everything on your car.
Reply to
serg
Thanks Serg,
Yeah, the FSM I have is the first thing I checked but it was not very telling that year I guess. Probably gets better as the years go by.
Thanks for the info.
Bill
Reply to
William Oliveri

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