Valve to piston clearance

Mopar Performance Issues

  1. dartlove

    dartlove Well-Known Member

    Messages:
    191
    Likes Received:
    35
    Joined:
    May 5, 2013
    Location:
    northern Ca
    Local Time:
    12:57 PM
    So I need some valuable advice, not asinine comments. I have a 383 that I stroked to a 496. My problem is that the block was decked so bad that the pistons are .023" out of the hole. I put on .060 cosmetic mls head gaskets to bump up compression slightly. Problem now is exhaust valve is hitting the piston. I am not sure what to do. Do I get a thicker gasket? Do I start over with another 383 and new machine shop. Or do I eat the almost $1900 in machine work & pistons and start over with a 400 block. Any viable help is appreciated.
     
  2. gzig5

    gzig5 Well-Known Member

    Messages:
    1,016
    Likes Received:
    960
    Joined:
    May 3, 2018
    Location:
    Mequon, WI
    Local Time:
    2:57 PM
    If there is enough meat on the piston, the valve relief can be made deeper. I'm not to familiar with big blocks but if you have 1.6 rockers go with a 1.5 ratio. Another option is to change the cam for something with less lift. Sink the valve seats in the head, but I don't think that helps flow any. I don't think a thicker head gasket is going to get you safe clearance without doing something else.
     
    • Agree Agree x 1
    • SGBARRACUDA

      SGBARRACUDA ROY FABO Gold Member

      Messages:
      15,855
      Likes Received:
      4929
      Joined:
      Dec 7, 2006
      Location:
      PLANT CITY FL. and PERRY GA.
      Local Time:
      3:57 PM
      What cam is it? Rocker ratio?
       
    • dartlove

      dartlove Well-Known Member

      Messages:
      191
      Likes Received:
      35
      Joined:
      May 5, 2013
      Location:
      northern Ca
      Local Time:
      12:57 PM
      I currently have harland sharp 1.5 rockers. Cam is custom grind 15601224089721956288201009866921.jpg
       
    • SGBARRACUDA

      SGBARRACUDA ROY FABO Gold Member

      Messages:
      15,855
      Likes Received:
      4929
      Joined:
      Dec 7, 2006
      Location:
      PLANT CITY FL. and PERRY GA.
      Local Time:
      3:57 PM
      Man that is a lot of cam. What are you planning to do with this car? Street? Race only?
       
      • Agree Agree x 2
      • dartlove

        dartlove Well-Known Member

        Messages:
        191
        Likes Received:
        35
        Joined:
        May 5, 2013
        Location:
        northern Ca
        Local Time:
        12:57 PM
        Race only. 64 dart
         
      • JBurch

        JBurch Well-Known Member

        Messages:
        1,805
        Likes Received:
        928
        Joined:
        Oct 17, 2009
        Location:
        Owego, NY
        Local Time:
        3:57 PM
        This probably isn't the answer you want to hear, pull the engine down and cut a deeper eye brow for exhaust valve clearance. While you are at it, double check the intake.
         
        • Agree Agree x 2
        • 4spdragtop

          4spdragtop Well-Known Member

          Messages:
          28,360
          Likes Received:
          8194
          Joined:
          Aug 28, 2009
          Location:
          Wasting time here
          Local Time:
          2:57 PM
          No engine expert here, but what about milling piston tops down? By another shop.
          Sorry to read.
           
        • toolmanmike

          toolmanmike FABO Staff Staff Member FABO Gold Member

          Messages:
          46,854
          Likes Received:
          31105
          Joined:
          Jan 18, 2006
          Location:
          Iowa
          Local Time:
          2:57 PM
          Milling pistons will just reduce compression. It won't effect valve to piston clearance unless you machine the pockets completely out. Machining the pockets deeper is the answer (if there's enough material) A simple piston swap would be a good plan if you don't want to switch cams.
           
          • Thanks! Thanks! x 1
          • brian6pac

            brian6pac Well-Known Member

            Messages:
            4,431
            Likes Received:
            2964
            Joined:
            Nov 15, 2016
            Location:
            N.E.Ohio
            Local Time:
            3:57 PM
            Did you degree in the cam ? If so what did you set it at.
             
            • Agree Agree x 1
            • krazykuda

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

              Messages:
              51,752
              Likes Received:
              16402
              Joined:
              Aug 20, 2007
              Location:
              Orland Park, IL
              Local Time:
              2:57 PM
              Your best option is to have valve reliefs/eyebrows cut into the pistons for valve clearance... But that cam has huge lift at .643"/.660" and will require deep cuts... You should check the thickness of the piston before machining to make sure that you will not break through the tops when making the valve reliefs deep enough for that much lift...

              Or see if there are any other pistons available with shorter dome and deeper valve relief pockets...
               
              • Agree Agree x 1
              • krazykuda

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

                Messages:
                51,752
                Likes Received:
                16402
                Joined:
                Aug 20, 2007
                Location:
                Orland Park, IL
                Local Time:
                2:57 PM

                Good point, but with that much lift and duration in that cam, I don't think that it's possible to 'degree' enough clearance for the valves...

                He needs pistons with deep valve relief pockets...
                 
                • Agree Agree x 1
                • krazykuda

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

                  Messages:
                  51,752
                  Likes Received:
                  16402
                  Joined:
                  Aug 20, 2007
                  Location:
                  Orland Park, IL
                  Local Time:
                  2:57 PM
                  383's and 426's are the same bore of 4.25", there should be some options out there with that common size of bore...
                   
                • dartlove

                  dartlove Well-Known Member

                  Messages:
                  191
                  Likes Received:
                  35
                  Joined:
                  May 5, 2013
                  Location:
                  northern Ca
                  Local Time:
                  12:57 PM
                  Degreed
                  I did. 108 centerline
                   
                • '63GT

                  '63GT Well-Known Member

                  Messages:
                  574
                  Likes Received:
                  465
                  Joined:
                  Jun 9, 2018
                  Location:
                  Turlock, CA.
                  Local Time:
                  12:57 PM
                  Brian6pak is correct!
                  If your exhaust valve is hitting before the intakes, your cam has not been properly phased in with the crank. and is most likely in a retarded position. (not the owner, the cam!)
                  The Int valve is a larger diameter valve and will always hit the piston before the exhaust does. (when the cam in installed correctly, or even straight up, or 0)
                  The cam card shows the cam in 2° ahead. (advanced) This makes the Intakes even closer to the piston at TDC.
                  The short of it.... slow down, double check your cam position, and decide accordingly.
                  If you find you need deeper valve releifs, Isky sells 'notch cutters', so that you can perform notches with the engine mocked up.
                  BTW, a .060 gasket will reduce your CR by more than a point..
                  also too. gross valve lift has absolutely NOTHING to do with how much valve clearance you will have, that is a function of duration at .050. (the valves are full open when the piston has swept waaaay down the cyl in crank degrees equal to the lobe centers.
                   
                  • Thanks! Thanks! x 1
                  • Agree Agree x 1
                  • dartlove

                    dartlove Well-Known Member

                    Messages:
                    191
                    Likes Received:
                    35
                    Joined:
                    May 5, 2013
                    Location:
                    northern Ca
                    Local Time:
                    12:57 PM
                    This is my first build of this magnitude. First time using milodon gear drive. (Still don't quite understand) . Thought I had it. When I did the clay neither valve touched. Also wasn't quite getting valve lift on intake according to cam card. It wasn't until I put all together prime and rotate that I run into problems.
                     
                  • SGBARRACUDA

                    SGBARRACUDA ROY FABO Gold Member

                    Messages:
                    15,855
                    Likes Received:
                    4929
                    Joined:
                    Dec 7, 2006
                    Location:
                    PLANT CITY FL. and PERRY GA.
                    Local Time:
                    3:57 PM
                    You need a clearance of .080 intake and .100 on the exhaust. No way your going to do it with head gaskets. You need to fly cut the pistons. If you have enough material.
                     
                  • dartlove

                    dartlove Well-Known Member

                    Messages:
                    191
                    Likes Received:
                    35
                    Joined:
                    May 5, 2013
                    Location:
                    northern Ca
                    Local Time:
                    12:57 PM
                    Thought I had knowledgeable help when I started this. Quickly found out I didn't . I do have another 383 block. Would it be worth a shot to find a different shop and try again? I only used the shop I did on recommendation. They used to build my father-inlaws Chevy comp eliminator motors. I do know of a good reputable shop an hour away.
                     
                  • dartlove

                    dartlove Well-Known Member

                    Messages:
                    191
                    Likes Received:
                    35
                    Joined:
                    May 5, 2013
                    Location:
                    northern Ca
                    Local Time:
                    12:57 PM
                    I am afraid I might be in over my head
                     
                  • SGBARRACUDA

                    SGBARRACUDA ROY FABO Gold Member

                    Messages:
                    15,855
                    Likes Received:
                    4929
                    Joined:
                    Dec 7, 2006
                    Location:
                    PLANT CITY FL. and PERRY GA.
                    Local Time:
                    3:57 PM
                    I think it would be worth looking into the possibility of cutting deeper valve reliefs than starting over.
                     
                    • Agree Agree x 2
                    • toolmanmike

                      toolmanmike FABO Staff Staff Member FABO Gold Member

                      Messages:
                      46,854
                      Likes Received:
                      31105
                      Joined:
                      Jan 18, 2006
                      Location:
                      Iowa
                      Local Time:
                      2:57 PM
                      Naw, just fix what you have. Degree the cam properly, cut the valve pockets if the pistons can handle it or change the cam if you have to. Your combo should be a screamer.
                       
                      • Agree Agree x 1
                      • brian6pac

                        brian6pac Well-Known Member

                        Messages:
                        4,431
                        Likes Received:
                        2964
                        Joined:
                        Nov 15, 2016
                        Location:
                        N.E.Ohio
                        Local Time:
                        3:57 PM
                        My friend has a 498 and he had the same problem, the cam was off and when I set it up right it had .080 clearance, his cam was a .600 lift, Ross flat top pistons that came out of the hole also not much but enough, I used .080 Cometic gaskets. It started out with 12.5 CR and I think we ended up with about 11.0:1 and It runs great. I would definitely double check the cam. The exhaust should not hit and the intake clears.
                         
                        • Like Like x 2
                        • dartlove

                          dartlove Well-Known Member

                          Messages:
                          191
                          Likes Received:
                          35
                          Joined:
                          May 5, 2013
                          Location:
                          northern Ca
                          Local Time:
                          12:57 PM
                          I have the trick flow 270's max wedge, indy 400B intake the cam specified, topped with an AED 1100. Car weighs 2660 with me in it
                           
                        • brian6pac

                          brian6pac Well-Known Member

                          Messages:
                          4,431
                          Likes Received:
                          2964
                          Joined:
                          Nov 15, 2016
                          Location:
                          N.E.Ohio
                          Local Time:
                          3:57 PM
                          Sounds like a cool car !
                           
                        • inertia

                          inertia Well-Known Member

                          Messages:
                          3,159
                          Likes Received:
                          487
                          Joined:
                          Feb 4, 2011
                          Location:
                          Victoria B.C. Canada
                          Local Time:
                          12:57 PM
                          As mentioned, your cam timing's outta whack.

                          The Toyota engines I race now have 20 thou shims to stack on the block when the factory turbo'd them.
                          Bigger turbo, more shims.

                          Back in the day, we tagged 4 - 5 welds on a sacrificial valve, sharpen, then use a piece of fuel line and clamp to limit the valve depth, and use an e!ectric drill to machine deeper valve reliefs.

                          Good luck.
                           
                          Last edited: Jun 9, 2019
                          • Like Like x 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.