318 pistons to bring compression up

Small Block Mopar Engine

  1. Slantsix64

    Slantsix64 Well-Known Member

    Messages:
    3,029
    Likes Received:
    1236
    Joined:
    May 11, 2014
    Location:
    SGV
    Local Time:
    2:51 AM
    ;QUOTE="moparmat2000, post: 1973318208, member: 14566"]Rusty, I am looking at a similar build on a 1977 318. I was looking at the KB167s. The stock pistons before dissassembly are about .100" in the hole at TDC. Arent the KBs a bit taller, closer to a zero deck height? The block will need to be surfaced "decked" anyways. The heads I have are rockauto reconditioned 302s. I have not CCd them yet to verify. Going to borrow a burette from a buddy of mine to get a number. I am ready to pull the trigger on a set of KBs but dont want to if they wont help get the compression up there.[/QUOTE]

    302 heads or 714 same head different part number will be at 64CC. With those KBpistons and 64cc head your CR will be pretty high im guessing in the 10:1 range but im not positive. If i were to use those pistons i would run a 360 cylinder head which are in the 72CC range and will lower your compression ratio if needed. it all about doing the math. good luck!
     
  2. moparmat2000

    moparmat2000 FABO Gold Member FABO Gold Member

    Messages:
    19,341
    Likes Received:
    8283
    Joined:
    May 13, 2010
    Location:
    Grand Tetons
    Local Time:
    2:51 AM
    I was reading that the average mid 70s 318 had a compression height on 1.720" and the KB167s are 1.810" that's a .090" difference that the Keith blacks bring it up out of the hole. Very little decking. Just enough to ensure head gasket sealing would probably be perfect with these.
     
    • Agree Agree x 1
    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

      Messages:
      73,160
      Likes Received:
      48640
      Joined:
      Jun 7, 2010
      Location:
      Georgia
      Local Time:
      3:51 AM
      I wouldn't take it off either.
       
      • Like Like x 1
      • Agree Agree x 1
      • yellow rose

        yellow rose Overnight Sensation FABO Gold Member

        Messages:
        28,537
        Likes Received:
        24967
        Joined:
        Jun 19, 2015
        Location:
        Central Washington
        Local Time:
        12:51 AM

        Yep, taking half of that off the block and half off the heads is still too much for the OE castings. They are way too thin and flexible to start with. If you start decking that much off it won’t hold head gaskets worth a crap.


        Doesn’t KB make a nice 318 piston that corrects that? I absolutely HATE the ring pack they use but the pistons are very nice.
         
        • Agree Agree x 1
        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

          Messages:
          73,160
          Likes Received:
          48640
          Joined:
          Jun 7, 2010
          Location:
          Georgia
          Local Time:
          3:51 AM
          Yes, but I believe the OP is looking for budget.....at least that's my impression. But Lord yes, if he can swing the KBs, that's a great way to do it!
           
        • C2ndLTpigeon

          C2ndLTpigeon Mopar or no Car! FABO Gold Member

          Messages:
          522
          Likes Received:
          125
          Joined:
          May 18, 2019
          Location:
          Indio California
          Local Time:
          12:51 AM
          Yes that is correct, Budget would be nice. Im thinking a slight overbore, with some stock heads with some at home port and and smoothing of the castings should help it out, I may just make a cleaner engine and keep my Whiplash cam since it is fun to drive I just regret not cleaning up the heads and one cylinder had a slight scar that I wish I would of overbored. Just wanted to see if there was a piston change to boost comp a tad but it seems like more more work and money than the gain is worth.
           
        • James Clews

          James Clews Well-Known Member

          Messages:
          157
          Likes Received:
          186
          Joined:
          Aug 25, 2018
          Location:
          Australia
          Local Time:
          5:51 PM
          Yes I put KB 167 pistons in my 318 and it measured from the lowest to highest was .015 to .011 . Only 4 thou difference so I did not deck it, just ran it as it was with a 62cc head and .039 gasket it came out at 9.7 to one.
           
          • Like Like x 2
          • YY1

            YY1 Well-Known Member

            Messages:
            7,871
            Likes Received:
            3499
            Joined:
            Oct 11, 2011
            Location:
            FL
            Local Time:
            3:51 AM
            Don't bore it if it don't need it.
             
            • Like Like x 1
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              19,341
              Likes Received:
              8283
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              2:51 AM
              Gonna have to on my sons. Pretty wore out stock bore. The .030" KBs will likely be the ticket. Not sure .020" is gonna clean it up all the way.
               
            • stumblinhorse

              stumblinhorse Well-Known Member

              Messages:
              253
              Likes Received:
              88
              Joined:
              Jan 9, 2018
              Location:
              Grand County, CO
              Local Time:
              1:51 AM
              So why don’t the kb399’s get mentioned to raise compression?
               
            • C130 Chief

              C130 Chief Mechanical Genius

              Messages:
              3,088
              Likes Received:
              249
              Joined:
              Nov 23, 2005
              Location:
              Boise, ID
              Local Time:
              1:51 AM
              Isn't the KB399 is a forged KB167?

              There used to be TRW 11.5 domed pistons available for the 318. Gave around 10:1 with 340/360 heads and a Fel-Pro composition head gasket. Don't know if these are still available.
               
            • stumblinhorse

              stumblinhorse Well-Known Member

              Messages:
              253
              Likes Received:
              88
              Joined:
              Jan 9, 2018
              Location:
              Grand County, CO
              Local Time:
              1:51 AM
              no a kb167 is a +5cc flat top and a kb399 is a -6.2cc dome. Everything else is the same. Both are Hypereutectic aluminum.
               
            • RustyRatRod

              RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

              Messages:
              73,160
              Likes Received:
              48640
              Joined:
              Jun 7, 2010
              Location:
              Georgia
              Local Time:
              3:51 AM
              Probably because that could get compression a little too high. Nice dang piston though!
               
              • Like Like x 1
              • krazykuda

                krazykuda Well-Known Member FABO Gold Member How-To Section Editor

                Messages:
                59,046
                Likes Received:
                24762
                Joined:
                Aug 20, 2007
                Location:
                Orland Park, IL
                Local Time:
                2:51 AM
                If you want a 318 to end up at 9.2 compression, get a set of 318 pistons with 10.5 compression, then put 340/360 heads on the engine and you will end up at 9.2 compression...

                Been there done that....

                Now you don't have to mill the block and/or head and then custom pushrods etc....
                 
                Last edited: Jan 26, 2021
                • Thanks! Thanks! x 1
                • RammerJammer75

                  RammerJammer75 Well-Known Member

                  Messages:
                  1,306
                  Likes Received:
                  1616
                  Joined:
                  Aug 28, 2020
                  Location:
                  Kingsport, TN
                  Local Time:
                  3:51 AM
                  I have a set of them in my 318 with the Indy MA-X heads. Calculated compression is around 11.5:1, but I'd say it'll be closer to 11:1.
                   
                1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
                  By continuing to use this site, you are consenting to our use of cookies.