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258 casting numbers

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Stormogdis View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stormogdis Quote  Post ReplyReply Direct Link To This Post Topic: 258 casting numbers
    Posted: Sep/15/2018 at 5:54am
I want to rebuild my 258 and want to know the year it was build.

Got som pictures of the numbers i could find.
The engine was pulled from my 73 matador, but i know it's not the stock engine.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 7:42am
corrected below


Edited by pacerman - Sep/15/2018 at 6:06pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 7:55am
hi, that engine is a 2 bbl 258 (C) built on  April 24. (04..24), probably in 1975, or if plastic valve cover, 1985.
george z
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stormogdis Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 12:43pm
Thanx.

Then i guess 85
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 1:38pm



Edited by pacerman - Sep/15/2018 at 6:04pm
Happiness is making something out of nothing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stormogdis Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 1:48pm
So it is a 1981
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 2:00pm
Corrected below

Edited by pacerman - Sep/15/2018 at 6:05pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 5:44pm
hi, not to confuse things, but I have an 82 factory TSM, looking at it right now, in it, it states that first digit "1" is 81, and first digit "2" is 82.
I also have an 84-87 TSM, again, looking at it right now, and it states that first digit "3", is 1983, and first digit "4" is 1984. So it would make sense that a plastic cover engine with first digit "5", is 1985.
Remember, the major design change occurred in 1981, (lighter crank, aluminum intake, etc), so, AMC started over with the number "1" in 81. The above engine is a 1985, 2bbl 258 with 9.2-1 compression.
I have a 1984 Eagle Sedan, which I know, beyond a shadow of a doubt, has its original engine, and its first digit is "4".
The 1979 and down numbers are correct.
The oddball year is 1980. First year of the Eagle, and this is the ONLY, "unlightened", block that will swap from a (2wd) Spirit/Concord directly into an Eagle (4wd). (has front axle mounting boss)
I have a 1980 block, first digit is "3", same as 1979, but after the main code, in smaller font, is stamped "80". AMC must have been planning a change, which they implemented in 1981.
btw, the 1981 engine had an 8.6-1 compression ratio, while the 1985 has a 9.2-1 compression ratio, really the only difference internally, though the engine management controls are/were very different. Much more sophisticated 84+, compared to 81-83, though that is moot in a 73 Matador!
btw, the above engine may have been rebuilt at some point, since it's painted AMC green/teal. All 82+ AMC 258s came "any color you want, as long as its black"  :)  no more engine color post 1982.
hope this helps, :)  thanks, gz
george z
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2018 at 6:07pm
Thanks.   I forgot about the date sequence change.   Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2018 at 6:56am
The engine design change occurred in calendar year 1980, so early 1980 model cars got the engine built in 79 (heavier model), late 1980 got the 1980 built engine. The lighter engine started to be manufactured in January 1980. So a 1980 model car could have either version.
Frank Swygert
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