Low Compression 451 Build

Big Block A body Tech

  1. 72DMag

    72DMag Well-Known Member

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    Hi All,
    I received a low miles 400 block (56k) and I plan to run the 400 as is for a while. Down the road I would like to go with a 451 because I already have a forged 440 crank. However, I would like to keep the compression as low as possible for the potential to do a turbo car. (I say this because I have 2 holset hx55 turbos from bigger cummins diesels sitting on the shelf in good shape).

    So, here's my questions:
    1. What can I do with the 451 to keep the compression low and close to the stock 8.2:1?
    2. With boost having the forged crank is a must but what about the rods and pistons and rings? any suggestions for those?
    3. Lastly for the potential of boost would it be better to grind the crank to make the 451? Or make the mains larger on the 400 block?

    Thanks for any input! Again this is down the road but would like to get an idea of materials and cost for this build now.
     
  2. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    This'll do it.

    Platinum Series Pistons - 4.375 -24 Dished-440 Source
     
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    • Garrett Ellison

      Garrett Ellison Amateur driver on public roadway, do not imitate.. FABO Gold Member

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      The last information I had seen on the main journal size was that for a high power build like you are talking about that the premium performance main bearings were only available in the 2.75 inch main journal size, but this may have changed by now. I think that with two big honking turbochargers, I’d go with some Milodon caps and studs and leave the surplus metal on the crank.
       
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      • Garrett Ellison

        Garrett Ellison Amateur driver on public roadway, do not imitate.. FABO Gold Member

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        Oh, and a girdle, if you plan on exceeding 650 hp on a regular basis. But that’s just my $0.02. On the upper end, BCR cap and girdle system. So much need anymore for affordable aftermarket blocks with the power potential available.
         
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        • Ottmundr

          Ottmundr 68 Fastback

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          • pishta

            pishta I know I'm right....

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            Keep the mains, grind the crank. still plenty strong. Youll have to grind the throws down too. I have an HX35 Im gonna strap on a 273 if the stars align.
             
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            • 72DMag

              72DMag Well-Known Member

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              Thanks All. Yeah i am leaning toward leaving the surface area on the crank. i will have to look into a girdle. I agree that it will strengthen the bottom end and is worth the investment. For the reverse bowl pistons posted I hope that $600 is for a set of 8. If not Holy Cow Batman!!
               
            • Hemirunner

              Hemirunner Well-Known Member

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              Why not just leave it a 400 if you’ll be adding the turbos? Change the crank out with a forged 383 if you’re worried about it. If you find a good take out, that would also be the least expensive option. I’d add some ARP main bolts, bolt on the turbos and send it!
               
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