What AMC 6 is under my hood?

Discussion in 'General IH Tech' started by Wombat, Oct 9, 2018.


  1. Wombat

    Wombat Farmall Cub

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    I recently purchased a 1970 scout 800, build page here: http://www.binderplanet.com/forums/index.php?threads/self-sabotage-1970-800a.139661/.
    6E963320-BD14-4746-9734-29757A53AB28.jpeg
    I have the AMC i6 and assumed it was the 232 because that is what comes in scout 800’s but I removed the oil pan and the crank has 258 written on in grease pen.
    A13854B7-50A5-4A11-B7F0-65F29F06A358.jpeg
    C150A5B6-9019-4E4A-9973-F9CB7816D47B.jpeg
    How do I differentiate between the 232 and the 258? The only marking I can find cast into the block is 3199962, which can be found on both the 232 and 258.
    EA417EA3-E382-43A3-A840-8AB12A2C1EEE.jpeg
    Has someone swapped out the motor or just the crank? Can a 258 crank fit in a 232? What other mods would be required? I’m so confused, any guidance would be appreciated.
     
  2. Packerrailway

    Packerrailway High Wheeler

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    To the best of my limited knowledge, BOTH the 232 and the 258 of that era, used the same block. The deck height was raised in the 232 to accommodate the stroke of the 358 being 0.40" longer than that of the 232. Your engine might be a 'stroker' a 232 with a 258 crank. Some sources say that setup will produce more power than a stock 258.
     
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  3. Josh800A

    Josh800A Farmall Cub

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    Do you have the line setting ticket?
    Do you think it’s original?
    232 or 258, they’re good engines, but hard to connect to other IH bits and even AMC bits because the bellhousing changed in the early-mid 70’s.
    Mine runs great, btw.
     
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  4. Packerrailway

    Packerrailway High Wheeler

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    Change over of bell housings is reported to have happened for the 1972 MY. The change was to match the configuration of the AMC V-8 engines.
     
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  5. WRENCH MAN

    WRENCH MAN Dreams of Cub Cadets

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    What are the #'s stamped on the block pad by the distributor??, is the starter on the driver side or the passenger side.
    If you put a 258 crank in a 232 block you get a 258, NOTHING more, there should be a casting # on the crank its self, how many counter weights does it have on it?? are there clearance bumps for the connecting rods on the left side of the oil pan??

    There is an internet TALE!! of a short deck 258, supposedly the DJ postal Jeeps had them???, I'm going to call BS!! on that until I see one in the flesh!, they used up the short deck 232's in them.
     
  6. Howard Pletcher

    Howard Pletcher Farmall Cub

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    It was not built with that crank nor with a 258 as AMC did not begin production of the 258 until 1971.
     
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  7. Jeff Jamison

    Jeff Jamison Lives in an IH Dealership

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    I have been told,but don't know for sure 258 had starter on right side,232 had it on the left.
     
  8. Wombat

    Wombat Farmall Cub

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    I've been doing some research and the AMC i6 engines went through a couple of changes in the early 70's so see if you can fallow me:
    • 1964 the 232 was the first "modern" i6 AMC built. Settle down there scooter, i know they were building the 195.6 earlier but AMC completely redesigned the i6 in 1964 and there are features that followed the engine right up to the last 4.0 built in 2006 (which is amazing in my opinion that an engine can be robust enough to maintain roughly the same design for 42 years).
    • 1965 AMC begins manufacturing the 199 by putting a different crank and rods in the 232 (So they are the same engine but the 199 has a shorter stroke).
    • 1971 AMC stops manufacture of the 199 but starts building the 258. Now pay attention because here things start to get screwy. AMC increased the deck height of the engine block to create the 258 and scrapped the old shorter block, so now the 258 and the 232 are the same engine but the 232 is the one with the shorter stroke (the bore has remained the same throughout). This means that the pre-1971 232 is not the same block as the post-1971 232.
    • 1972 AMC re-designs the bell-housing on the 232 and the 258 to match their V8 bell-housing and the starter moved from the driver to passenger side. This is why they later 232 and 258 can mate up to a better variety of transmissions. The bell housing stayed this way until the end of the 4.0.
    • 1979 they stopped production of the 232, possibly due to the implementation of stricter emissions regulations.
    • 1990 they stopped production of the 258 a couple of years after AMC was acquired by Jeep and they begin the production of the 4.0
    • 1987-2006 Jeep manufactured the 4.0 which was based on the 258
     
    Last edited: Oct 10, 2018
  9. WRENCH MAN

    WRENCH MAN Dreams of Cub Cadets

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    As I stated above, I DO NOT! believe there is such a thing as a small belhousing 258!, they went to the bigger belhousing of the V8 to fit the stroke of the 258 crank, '71 and later AMC six's all have the V8 bell pattern.

    If you'd answer these questions it can be determined what you have,
    What are the #'s stamped on the block pad by the distributor??
    Is the starter on the driver side or the passenger side.
    There should be a casting # on the crank its self.
    How many counter weights does it have on it??
    Are there clearance bumps for the connecting rods on the left side of the oil pan or is it flat??
     
  10. Wombat

    Wombat Farmall Cub

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    Ok Wrench man, good call on the clearance bumps but things still seem funny, here is what I found:
    The engine no longer has the identifying tag, if it did I wouldn't have started this post.
    Also the pad by the distributor is blank. It's strange, there is a boss for a stamp but the boss is blank. I can take a photo if you don't believe me.
    Unfortunately, I already re-installed the oil pan and don't plan to remove it until I absolutely have to so I don’t have the crank stamp number or the number of counter weights.
    But you can see the stamp on the rear bearing cap in the photo above which looks like 3171A533.
    The oil pan does have clearance bumps for the connecting rods. See picture from when I had it off and was cleaning it before repaint.
    IMG_2342.jpg
    The starter is on the driver side.
    I have the 3 speed transmission.
    IMG_2796.jpg
    Here is the stamp found on the intake manifold 3191690 D1:
    IMG_2789.jpg
    What do you think?
     
    Last edited: Oct 11, 2018
  11. WRENCH MAN

    WRENCH MAN Dreams of Cub Cadets

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    :cornfused:HHMMM????
    I must say that this is the best evidence of the "MYTHICAL" '70 small bellhousing 258 that I've ever seen!?
    I'm not really familiar with the accessory's that were on the IH application AMC engines?, that pan is indeed a 258 pan, looks like a later '70's/'80's Jeep pan?, the car six's don't have that deep sump and they also don't have the clearance for the exhaust pipe crossover in front of the flywheel, the starter on the left side is a small belhousing, it would be nice to know the deck height of that block!, the casting # of 3199962 shows for '64-'80, so that's of little ID?
     
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  12. Jeff Jamison

    Jeff Jamison Lives in an IH Dealership

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    The deep pan with the skid plate was used on the early scoutII,my 73 had the same pan on it.
     
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  13. Wombat

    Wombat Farmall Cub

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    I had another look at the boss where the engine code should be and it’s not blank! It was just covered in about 4 coats of paint. I scraped some off and this is what I’ve found.
    9F5A628F-1EB7-41DC-B04A-88E03EAF57B0.jpeg
    Looks like 310 E 23. So it’s a 232 build in 1970 on October 23rd. Awesome!

    It’s still strange that a newer oil pan is used on a 70 block. I thought the bolt pattern changed.

    Next time I change the spark plugs (which will be soon) I will use a skinny rod and measure the stroke of the pistons and hopefully put this whole thing to bed.
     
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  14. Wombat

    Wombat Farmall Cub

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    Jeff, I’m going completely off topic here but among the scout II’s I think the 73 is the best looking year. I was close to buying one just before I found my 800. I prefer the 800 body style but maybe my next scout will be a 73.
     
  15. Wombat

    Wombat Farmall Cub

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    Josh,
    How do you get the line setting ticket? I need to pick one up.

    You are right, these AMCs seem to be pretty durable little engines. I was not a fan when I purchased the truck, I was mostly interested in the condition of the body, but this thing runs much better than I expected. My initial plan was to swap it out first chance I got but now I’m going to keep it going as long as I can. This is why I’m so curious about figuring out exactly what the damn thing is.
     
  16. Wombat

    Wombat Farmall Cub

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    Packer,
    You might be right, someone may have just swapped the crank out. But like wrench man mentioned I think it would just be equal to a 258 because the bore and stroke would then be the same. The crazy thing is this block seems to be a 1970, and according to the internet, the 258 crank shouldn’t to fit. The deck height change didn’t occur until 1971.

    Damn I wish I had been smart enough to look for the crank stamp while I had the oil pan off.
     
  17. Howard Pletcher

    Howard Pletcher Farmall Cub

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  18. WRENCH MAN

    WRENCH MAN Dreams of Cub Cadets

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    The only thing that seems to be really out of place then is the fact that someone hand wrote "AM258" on the crank?, the only differences in the 232 vs 258 of the same vintage are the crank and connecting rods, EVERYTHING else is the same, if the block was bored a kit for a 258 is indeed one in the same for a 232, a 199 used flat top pistons vs the dished of the two bigger engines, the problem here is that a 258 crank in a short deck block should have the pistons sticking out of the deck!?

    The oil pan seems to be an oddity for this year model too?, it shouldn't have the rod clearance bumps?, and I know for a fact that there are two different oil pan bolt patterns too!, I would assume "early" and "late", but I don't know when the change over happened?, I would have assumed in '71 with the block change?

    This defiantly a chin scratcher!
     
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  19. Wombat

    Wombat Farmall Cub

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    I pulled a spark plug yesterday and used a thick copper wire to measure the stroke while I turned the crank manually. The stroke of the 232 is 3.5” and the 258 is 3.895”.

    Because the wire must be held at an angle to feed through the spark plug fitting the measured distance will be greater than the actual stroke. I measured a 4.25” difference between the top and bottom of the stroke and based on my eye ball measurement of the wire I would say I was holding it close to a 20° angle.

    Doing some quick trig shows that if the wire was held at 34.5° then it is a 232 and if the wire was held at a 23.6° angle it is a 258.

    This gives me confidence that this motor is a strange beast. And so far, I’m guessing it’s a 258.

    I have some additional good/bad news. The oil pan still drips… The drip is much slower but it pisses me off so I will likely re-do it sometime this winter which will give me an opportunity to have a better look at the crank shaft.
     
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  20. Packerrailway

    Packerrailway High Wheeler

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    Before you remounted the oil pan, did you check to make certain that the mating surface was flat and true? IF the bolt holes are "above" the rest of the mating surface, you'll never get a good seal. To 'fix' place some bar stock under the flange and use a small hammer to tap firmly and flatten the mating surfaces uniform all the way around. At least where there are bolt holes.
     
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