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304 Question

Discussion in 'Intermediate CJ-5/6/7/8' started by kiowamtp, May 18, 2020.

  1. May 18, 2020
    kiowamtp

    kiowamtp Member

    DFW
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    New to 304's and starting to do some planning. I see several different 304 available...international, obviously AMC, etc in various years. As I have been researching seems like different years had different specs. Any pitfalls using IH 304 vs AMC. Direct bolt on?

    I am looking for a fairly easy build and swap. I have a few IH 304 and some AMC's around me. Just wondering what I should be keying in on.

    Also, what would one expect to pay throughout the life cycle of a build. Block and heads inspected and possibly machined and new internals. I am weighing buying a reman 304 or build my own. Thanks
     
  2. May 18, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    You are dreaming. "304" is only the displacement and has nothing to do with the design and compatibility between brands. The International 304 is completely different from the AMC 304. Using anything IHC will be weird, surprising and expensive.

    A swap to a modern Chevy would be easier and make more sense that using the oddball IHC engines. What are you wanting to do? What's wrong with the core engine you have now?

    Discussing the trade-offs would require a book, easily. What is your skill level, how much are you willing to take on, how much can you or are you willing to spend, how will the vehicle be used, what do you expect from the result ... all factors in any "optimization" of the outcome.
     
    Last edited: May 18, 2020
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  3. May 18, 2020
    kiowamtp

    kiowamtp Member

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    Thanks Tim. I really just want to get it running and driving. TBH the cheapest way utilizing the existing drivetrain. So a 304 or whatever you call it...AMC 304 (?) I would think would be the quickest. My existing one is a cobble. I guess looking at it is kind of overwhelming. There are hoses and crap not hooked up and spark plugs for plug in the manifold and I was thinking it would be easier to get a block, get it checked and start moving stuff over. But then I started thinking short block reman but are there certain blocks I should be looking for; that is which ones are direct. There are a few 304's of later CJ5's available but non around my year range. You start looking at sites and it can be overwhelming for a layman when they start talking varying design changes, cast iron, post 79 304's and their changes, etc etc.

    I know I should just pull mine and strip it and start over but would the cost outweigh buying a shortblock? Originality is not a factor here. Should I be considering other engine options that would be a simple swap? Thanks
     

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    Last edited: May 18, 2020
  4. May 18, 2020
    duffer

    duffer Rodent Power

    Bozeman, MT
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    For your goal, you should stick to the AMC engines. You have a rather large selection, all of which will bolt in. 290, 304, 343, 360, 390, & 401. I would guess the 360 would be the most available as it was utilized across a bunch of models. It likely also has the best support for parts. The 290, 343, 390 were the early short deck engines and I would only use one if it didn't require any work. A 360 swap for a 304 is common.

    But before you do that, find out what you actually have. Run a compression check, both wet and dry. If the results of that and the oil pressure are within spec, there is no reason not to use your present engine. Cleaning up the external stuff requires relatively little effort.
     
  5. May 18, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Yes, there are more AMC 360s out there than 304s. Note that with 360s you have the same issue with the IHC 304 and the AMC 304 - the displacement is only coincidentally the same. Chrysler and Ford both had 360s that are completely different from the AMC 360. If you want the most performance for the dollar, the AMC 360 is probably it. You would need a complete 360 engine including harmonic balancer and flywheel.

    I would avoid the Gen 2 AMC engines: 240, 343, 390. Stick with the Gen 3 AMC engines: 304, 360, 401. (The 401 is exotic and out of your price range, I'd think. And adds significant pitfalls regarding condition and building of the engine.)

    Really, what's wrong with the engine you have? If you want to rebuild an engine, I'd say use what you have unless it has a hole in the block, broken crank, something really bad wrong with it. The 304 will power a CJ-5 just fine, maybe more than it should be powered. As John suggests, measuring oil pressure and compression would be my first step. If there's nothing seriously wrong with this one... there's no significant difference from beginning to end of the 304's run that I know of, except for maybe the earliest examples from '71 or '72.

    Your engine compartment does not look bad or unusual, just dark. The spark plugs are just a convenient 9/16"-18 plug for the air injection tubes, which you can easily replace. Get in there, clean it up, square it away, one component at a time.
     
    Last edited: May 18, 2020
  6. May 18, 2020
    kiowamtp

    kiowamtp Member

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    Well my 304 is an unknown. The PO rewired the Jeep. He says a cylinder lost compression and it has been sitting in a garage for over 4 years. During that time he says he was upgrading the distro and/or electronics and could not get it running again. He is not mechanically inclined and TBH I am more mechanically inclined but have never pulled a complete engine nor rebuilt the crank, pistons, and camshaft. I am not against the task. I am a hands on guy but I guess I was thinking a short block reman would take all the unknowns out, that is reduce my learning curve and negate the chance of me have a $1000 f up. However, I do have the Jeep service manual for that year. I guess talking through this I should start a process of getting it to crank and do a leak down and compression test and go from there. Thanks for the responses and allowing me a medium to work this out in my head.
     
  7. May 18, 2020
    kiowamtp

    kiowamtp Member

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    Just for my knowledge in case I do have to go that route what is considered a gen 3 AMC?
     
  8. May 18, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Gen 1: 250, 287, 327 - big heavy block, typical 1st generation V8.
    Gen 2: 290, 343, 390 - new light-weight engine from AMC, ca 1966.
    Gen 3: 304, 360, 401 - revision of Gen 2 with better cylinder head design and longer stroke, ca 1970.
    AMC V8 engine - Wikipedia

    You can identify these engines 1) they have the right features for an AMC V8 (ie right location for distributor, right valve covers), 2) the displacement "304" or "360" or "5.9L" or "401" cast in big letters into the driver's side of the block, 3) they should have a tag on the passenger side valve cover with the build date and engine code. Look at any TSM for decoding this tag. 304 is "H", 360 is "N" or "P" and 401 is "Z."

    Get your compression gauge and oil pressure gauge and measure. Don't guess, measure. Measure, measure, measure! Get it running - you can do it. Getting a junkyard engine running will be no easier than getting this engine running. Gas plus spark will fire.
     
    Last edited: May 18, 2020
  9. May 18, 2020
    sterlclan

    sterlclan Member 2022 Sponsor

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    a reman short block is always a risk as you have no idea what they started with. i would at least look at what you have and go from there...
     
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  10. May 19, 2020
    kiowamtp

    kiowamtp Member

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    Thanks everyone. I am going to be patient and get to the CJ5 when my other project clears my garage space.
     
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