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    885 piston to head clearance

    Looking for advice on how much P2H clearance I should be aiming for. 885 head, Mahle Stroker pistons (IE), M52 crank + steel rods (fresh small end bushings), NA engine, DD, so not going to see 6500+ very often.

    Found a few different numbers:

    https://www.hotrod.com/articles/ideal-quench-height/

    Quench should be as tight as possible without the piston actually contacting the head. This, in turn, is largely dependent on the type of connecting rods and the engine’s peak rpm. A good rule of thumb is that you can run as little as 0.038 to 0.043 inch with steel connecting rods. Steel-rod street engines that don’t see the far side of 6,000 rpm may even be able to shave this to as close as 0.032 inch. Aluminum rods expand and get longer with heat, so the quench clearance with them should be increased to 0.050–0.065 inch.

    https://speedtalk.com/forum/viewtopi...31132&start=30

    Don't spend too much time thinking about quench, get it under .050" & above .035" at the squish band & call it good.

    http://garage.grumpysperformance.com...h-squish.4081/

    If you are building an engine with steel rods, tight bearings, tight pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage.

    #2
    about 1mm

    Comment


      #3
      I'd aim for 1mm +/-0.1mm
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

      Comment


        #4
        When I developed those pistons I made sure that they little pamphlet that came with the pistons had that info in there. Was it not there?

        Here's another link, unfortunately photobucket nuked the pictures. The information is still the same though.
        https://www.r3vlimited.com/board/sho...&postcount=281
        ADAMS Autosport

        Comment


          #5
          I think he means piston to head clearance not piston to valve clearance
          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

          Comment


            #6
            Originally posted by digger View Post
            I think he means piston to head clearance not piston to valve clearance
            Correct. Thanks for the answers Digger & zaq123 - much appreciated.

            @skifree, thanks for the link - any/all relevant info is helpful. The box does include an A4 sheet about piston-to-bore clearance, piston material composition and basic info on bore size, crank/rod compatibility etc (same stuff found on the IE website). Nothing on minimum/ideal P2H (quench) clearance.

            Edit: there is also the Mahle Motorsport pamphlet which provides guidance on ring-end gaps and ring offset/orientation.

            Comment


              #7
              Like Andrew said, Mahle should had a booklet in the kit.

              Mahle recommended Piston to Head clearance From the booklet: steel rods - 0.040" or 1.016mm; alum. rods -0.060"

              Comment


                #8
                Originally posted by Lugnuts View Post
                Correct. Thanks for the answers Digger & zaq123 - much appreciated.

                @skifree, thanks for the link - any/all relevant info is helpful. The box does include an A4 sheet about piston-to-bore clearance, piston material composition and basic info on bore size, crank/rod compatibility etc (same stuff found on the IE website). Nothing on minimum/ideal P2H (quench) clearance.

                Edit: there is also the Mahle Motorsport pamphlet which provides guidance on ring-end gaps and ring offset/orientation.
                it's on the page 2 of Mahle booklet. Not A4 IE print out

                Click image for larger version

Name:	M20 MahleMotorsports Pamphlet 2.jpg
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                Comment


                  #9
                  Interesting. Either I've somehow managed to lose it, or it wasn't included. The Mahle pamphlet I have is small (like A5 size), and only talks about the rings.

                  Comment


                    #10
                    Hey.... there it is. Thank you Zaq. Sorry for the mixup, I knew it was in the same pamphlet. There is one in every set.
                    ADAMS Autosport

                    Comment


                      #11
                      Originally posted by Lugnuts View Post
                      Interesting. Either I've somehow managed to lose it, or it wasn't included. The Mahle pamphlet I have is small (like A5 size), and only talks about the rings.
                      weird. There should be 2 pamplets, one for rings and one for pistons.

                      Here is page 1 for pistons. Hope it helps. I like Checklist for Success part, truth is told there. Some folks did good work to rebuild M20s, failed to check things and screw up their hard work...as documented on this forum a few times


                      Click image for larger version

Name:	M20 MahleMotorsports Pamphlet 1.jpg
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                      Last edited by zaq123; 09-04-2018, 03:40 PM.

                      Comment


                        #12
                        Originally posted by SkiFree View Post
                        Hey.... there it is. Thank you Zaq. Sorry for the mixup, I knew it was in the same pamphlet. There is one in every set.

                        you are the one who did the hard part, including these scans ...so Thank you

                        Comment


                          #13
                          Yeah I definitely don't have that. It's entirely possible I've misplaced it, since I bought the pistons 2 years ago. Anyway, doesn't matter! Thanks @zaq123, that's super helpful. Copies saved for (near) future reference.

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