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Thread: L24 or L28

  1. #1
    Registered User 1970Datsun240z's Avatar
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    Default L24 or L28

    Hey all,
    I tried searching a bunch before starting this thread but I still don't quite have answers that I need.

    I have two engines:

    Block-l28,N42
    Head-N42
    (in the car now with SUs)

    Block-l24
    Head-N42


    I have to double check the block casting number on the l24 engine but it was out of a 1971 240z.

    The l28 in it now is showing signs of well... Being a 35 year old engine.

    I want to rebuild one of these engines but which one? I don't want to do anything that crazy as money is an issue. I read that using some of the parts from the l24 and into the l28 is an idea??

    Also, is the N42 a good head? Should I try to look for an E31, P79, etc?

    Anyone know of an engine shop that has done Datsun engines up here in the Northwest? The closer to North Idaho the better.

    I bought the 1971 240z as my parts car and it had quite a few high performance items on it. I have no idea what has been done to the engine. It would have been a nice car itself except it sat for a few years and really rusted. I plan on taking the engine all apart sometime soon. Would you guys be able to tell what has been done to it with just pictures?

    Thank you all sooooo much for looking at this topic once again.

    John
    '70 Datsun 240z. HLS30-12161.
    Built from the ground up.
    Check out my blog at: zrestoration.blogspot.com
    CZCC #19152

  2. #2
    Registered User 1970Datsun240z's Avatar
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    Default

    The block on the L24 is a P30.
    Also, on the topic of gas mileage. I am getting like 14-15 mpg. Quite miserable. Is this just because my engine is on its way out or is there another problem? My dad and I just rebuilt my SUs and they are working quite amazingly now but my gas mileage is still bad.

    Thanks,
    John
    Last edited by 1970Datsun240z; 09-09-2010 at 03:30 PM.
    '70 Datsun 240z. HLS30-12161.
    Built from the ground up.
    Check out my blog at: zrestoration.blogspot.com
    CZCC #19152

  3. #3
    AZ Z Fan duffman's Avatar
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    Default

    Here are some thoughts by Diseazd in this thread:

    http://www.classiczcars.com/forums/s...threadid=39720
    January 1970 240Z
    HLS3001399

  4. #4
    Registered User 1970Datsun240z's Avatar
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    Default

    Thank you I just saw that. One thing I don't understand is why use the L28 pistons? Aren't they supposed to be dished and the L24 has flat tops? Maybe I'm understanding wrong but I thought flat tops would be better.

    John

    edit- I just realized that the L24 pistons probably don't fit in the L28 block so unless you get new pistons you have to use the L28 pistons if you use the L28 block.
    Last edited by 1970Datsun240z; 09-09-2010 at 04:38 PM.
    '70 Datsun 240z. HLS30-12161.
    Built from the ground up.
    Check out my blog at: zrestoration.blogspot.com
    CZCC #19152

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    Default

    Beyond what Guy said, which is all good, the block will dictate to the machine shop and you what's needed vs. what can be reused. As far as machine shops are concerned for a driver engine a good machinist need not be schooled skilled and up to speed on Datsun specific hardware. Open the book, find the page, set up the machine and stand by.....
    Bruce Palmer
    Salem Or
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    503-587-9800

  6. #6
    Supporting Member Diseazd's Avatar
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    John.....You're right.... L28 flat-tops are better.....use the flat tops from the later L28 blocks. Put new flat top L28 pistons on your L24 rods......never ever take an old piston off of one rod and put that same piston on another rod. However, if you can find L28 rods with flat top pistons from another engine, you can re-ring the pistons and go with that. Good Luck!
    http://www.flickr.com/photos/1404980...7600346077563/
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    70, 71, 2 72's, and a 73 240z....
    90 300zx and a 1996 Acura NSX.....but who's counting?

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    Registered User 1970Datsun240z's Avatar
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    Thanks a bunch for the info. It Really helps.

    It might not be for a little while but when I take the L24 apart I'll post some pictures. Who knows what I'll find in there!

    John
    '70 Datsun 240z. HLS30-12161.
    Built from the ground up.
    Check out my blog at: zrestoration.blogspot.com
    CZCC #19152

  8. #8
    Registered User 1970Datsun240z's Avatar
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    Hey again,
    I took the L24 is all apart and it is beautiful!
    It looks like it was rebuilt and then just sat. So I'm going to get all new gaskets, maybe new rings for the pistons, it's in such good shape I don't know what else there is to do!!! It still has the scratches in the cylinder walls from them being honed!

    I also found a plate on it that you can see in the last picture. I looked them up online and they are an engine remanufacturing place. I'm going to try and get ahold of them to see what they can tell me about the engine since it has a number on the plate.

    I also contacted a machine shop near by and they are going to look my head over for cracks and check the valves and all that.

    There are some numbers on the end of cam: DA 272 2 1c CRANE -NC 168-29-81 x
    And then actually on the cam it has: D2 and CWC
    Do those mean anything to you guys?

    I scrubbed the block down (second to last pic) and I hope to paint it pretty soon.

    Thanks,
    John
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    Last edited by 1970Datsun240z; 09-17-2010 at 04:00 PM.
    '70 Datsun 240z. HLS30-12161.
    Built from the ground up.
    Check out my blog at: zrestoration.blogspot.com
    CZCC #19152

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