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Help me determine my piston-to-head clearance!

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    Help me determine my piston-to-head clearance!

    Hello everyone,

    Today while beginning the assembly of my engine (F22b2 bottom end, F22a1 head, with 86mm arias 8.2:1 CR pistons, Darton dry sleeves) I realized I have an issue. My piston-to-head clearance is not enough, actually its negative, which means if I had tried to assemble the engine as-is the pistons would hit the cylinder head as soon as I would have rotated the crank.

    Anyway, I just got my block back from the machine shop to have the Darton dry sleeves installed, and also had the cylinder head decked. During the machining obviously enough material was taken off to take away that clearance which is needed for obvious reasons.

    I would imagine the simplest was to fix this now is to get a slightly thicker head gasket to accomodate that spacing there that I need, am I correct in my thinking here? Getting a new thicker head gasket shouldnt be too hard, but what I need to figure out is the ideal piston-to-head clearance should be, so I can calculate what head gasket I need to get, and so the engine performs the way it should without any big issues!

    EDIT: 4/14/12 I ended up machining the top of my pistons, Read on for more info!!

    If anyone can give me any suggestions on this that would be greatly appreciated! Also if anyone has any idea what the stock piston-to-head clearance on our engines are, that would be a great help also.

    Block: F22b2 - essentially identical to the F22a1, a4, a6.
    Head: F22a1
    Current head gasket - MLS .030" - not enough!
    Arias pistons 86mm 8.2:1 compression ratio
    Car is turbocharged currently - DSM 16g setup- with future plans to re-introduce the nitrous oxide.

    Here you can see my clearance issue. Note: this is exactly at top dead center.:



    If i measure that clearance above, which is how far the piston extends from the block I get this, which when added together is .037"



    And a quick pic of the Darton dry sleeves

    Last edited by ON_N20; 04-14-2012, 10:56 PM.
    ON_N20
    Nitrous = Been there. Turbo = Now. Nitrous + Turbo?... LOADING

    #2
    dude ur golden! have the same setup.bisi aris 8.2:1 with the long ratio rods.same thing nice lip from the pistons..for the 5mins i had mine runing,used a stock h23 head gasket from advanced auto and worked fine...had to remove head to swap back to a stock block because of issues due to previous owner.

    my new turbo build

    Comment


      #3
      Hopefully the person who helps you can help me. I have a piston out the block issue. I will have to find my old phone to post pics. Nice build though.

      Comment


        #4
        Originally posted by Youngill726 View Post
        Hopefully the person who helps you can help me. I have a piston out the block issue. I will have to find my old phone to post pics. Nice build though.
        Thanks. Yeah hopefully I can find an answer. Ive found a few online stores that make custom copper headgaskets in alot of different thicknesses, so I think thats about my only cheap option at this point, other than getting a new set of pistons with a lowered wrist pin, which would set me back a bit

        I ran these pistons for about a year boosted in my last block before I split a cylinder, 1mm overbore on a stock block doesnt last long on boost, so I figured at least the dry sleeves would help a bit, but now I have this issue which will probably suck some more cash down the drain to fix lol.
        Last edited by ON_N20; 03-24-2012, 08:25 PM.
        ON_N20
        Nitrous = Been there. Turbo = Now. Nitrous + Turbo?... LOADING

        Comment


          #5
          Originally posted by 92smokeaccord View Post
          dude ur golden! have the same setup.bisi aris 8.2:1 with the long ratio rods.same thing nice lip from the pistons..for the 5mins i had mine runing,used a stock h23 head gasket from advanced auto and worked fine...had to remove head to swap back to a stock block because of issues due to previous owner.
          The head gasket I have now measures out at just under .030" compressed:



          That means that the piston interferes with the head by about .007" which would spell disaster if I just assembled it as is right now, and attempted to start it

          Heres a nice pic to help others understand. My pistons currently extend past the top line of the compressed head gasket thickness, hence the problem:

          Last edited by ON_N20; 03-24-2012, 08:25 PM.
          ON_N20
          Nitrous = Been there. Turbo = Now. Nitrous + Turbo?... LOADING

          Comment


            #6
            Why didn't your machine shop have the pistons and rods in hand when they were machining the block?
            My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

            Comment


              #7
              Originally posted by Jarrett View Post
              Why didn't your machine shop have the pistons and rods in hand when they were machining the block?
              Actually they did, they needed them to check the finished bore size. They also had the original piston tech sheet. My rods are forged h-beams, but are the OE length, and so is the crank. I'll have a talk with them during the week and let them know whats going on. Regardless, I still need to determine the correct piston-to-head clearance so I can figure out which thickness of headgasket I'll need now. Whether or not they can reimburse me in any way is anyones guess lol.
              ON_N20
              Nitrous = Been there. Turbo = Now. Nitrous + Turbo?... LOADING

              Comment


                #8
                id just have cometic make you a .60 or just get a 5 layer headgasket. the aftermarket companies have a 5 layer. i can measure you one if you want and it will fit a 86mm.
                I <3 G60.

                0.5mm Oversized Stainless valves and bronze guides available. Pm me please.

                Comment


                  #9
                  Thanks yeah I think those are my best options. If you do have a 5 layer hanging around that you could measure for me that would help alot! I would have to assume a 5 layer headgasket would be in the area of .050", simply because the head gasket I have now is 3 layers, with .030" total, so each layer must be approx .010".

                  Otherwise Cometic can make me a gasket for sure, although that could get a bit pricy compared to an off the shelf gasket.

                  I havent yet found a 5 layer headgasket in the aftermarket but then again I havent searched every corner of the internet yet, I'll have to take a look again.

                  On another note, assuming the 5 layer is around .050", and my pistons extend from the block deck surface by about .037", that would leave me a net piston-to-head clearance of only about .013". Im not sure if that is going to be enough or not. Take into consideration the expansion rates of the rod, piston, and even crank as they heat up, as well as the slight stretch the components experience during high rpms.

                  I was reading about high performance engine building, and there is alot of info concerning this, because too small of a space, even though it clears, can cause turbulence and heat etc. as the piston nears the top, that volume of air gets compressed and pushed aside, which can be a bad thing, depending on the situation. Its pretty complex I guess, and does make a difference.

                  Thanks for all the help everyone I still would like to know the factory spec for our F-series stock piston-to-head clearance, that would help alot, if anyone knows off hand!
                  ON_N20
                  Nitrous = Been there. Turbo = Now. Nitrous + Turbo?... LOADING

                  Comment


                    #10
                    Originally posted by ON_N20 View Post
                    Thanks yeah I think those are my best options. If you do have a 5 layer hanging around that you could measure for me that would help alot! I would have to assume a 5 layer headgasket would be in the area of .050", simply because the head gasket I have now is 3 layers, with .030" total, so each layer must be approx .010".

                    Otherwise Cometic can make me a gasket for sure, although that could get a bit pricy compared to an off the shelf gasket.

                    I havent yet found a 5 layer headgasket in the aftermarket but then again I havent searched every corner of the internet yet, I'll have to take a look again.

                    On another note, assuming the 5 layer is around .050", and my pistons extend from the block deck surface by about .037", that would leave me a net piston-to-head clearance of only about .013". Im not sure if that is going to be enough or not. Take into consideration the expansion rates of the rod, piston, and even crank as they heat up, as well as the slight stretch the components experience during high rpms.

                    I was reading about high performance engine building, and there is alot of info concerning this, because too small of a space, even though it clears, can cause turbulence and heat etc. as the piston nears the top, that volume of air gets compressed and pushed aside, which can be a bad thing, depending on the situation. Its pretty complex I guess, and does make a difference.

                    Thanks for all the help everyone I still would like to know the factory spec for our F-series stock piston-to-head clearance, that would help alot, if anyone knows off hand!
                    My Evergreen gasket I got off Ebay from Mizumo Auto is a 5 layer. When I got it I thought I had got 2 on accident. I paid $19.97 no shipping...
                    Originally posted by Mishakol129
                    Do not disrespect my intelligence. I am the smartest person I know : )

                    Comment


                      #11
                      same, i have a used one inf ront of me...an "eristic" gasket bought off ebay. the 5 layers are probably close to .060 but i don't have my mic or calipers on me
                      I <3 G60.

                      0.5mm Oversized Stainless valves and bronze guides available. Pm me please.

                      Comment


                        #12
                        The quench areas between the F22A head and pistons actually work well with tight clearances. The squish of the air fuel mixture will not be turbulent, nor will it overheat. It should actually benefit your combustion via a more complete burn and a cooling effect.

                        You need to know how much material was removed from the block and the head in order to calculate your piston to deck and piston to valve clearances. The stock F22 P2D clearance is -0.002 (POH) to begin with. The more material you remove from the deck the more the piston will be out of the block. Add the material removed to 0.002" and you have your P2D clearance.

                        To be honest, if you have everything there, the best way to measure your clearances would be to clay the engine. Then you can order a head gasket to give you your proper clearances.

                        What clearances are you shooting for anyway? 0.035"-0.045"
                        Last edited by GhostAccord; 03-27-2012, 11:46 PM.
                        MR Thread
                        GhostAccord 2.4L Blog

                        by Chappy, on Flickr

                        Comment


                          #13
                          Sorry, just noticed that you used a pair of feeler gauges. So going by your 0.037" measurements, they took 0.035" off your block....did they say why? How much did they take off your head?
                          MR Thread
                          GhostAccord 2.4L Blog

                          by Chappy, on Flickr

                          Comment


                            #14
                            I'm with Ghost on this one. I understand decking a block after installing sleeves to relevel the deck surface. However you shouldn't need much to accomplish that at all. .035" is crazy and if it were mine I would consider it ruined and make the machine shop buy me a new block. Not because it can't be managed but because you're having to make considerations you shouldn't have to. Right off the bat you'll be spending $130 on a custom head gasket if the 5-layer doesn't work.

                            Or you could run a set of K20 pistons. 86mm bore and a 30mm compression height.
                            My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

                            Comment


                              #15
                              Ive got a 5 layer made by evregreenauto (ebay) it measures .075 thickness and im squeazing it pretty good with starrett mics.

                              But like Jarret and Ghost said id get ahold of the shop that did the machine work

                              http://www.cb7tuner.com/vbb/showthread.php?t=187851
                              sold to: cb7rush\h22-accord\Luis\BurtonRiderT6
                              bought from:jokerxfn-tommi-'93cb7ex

                              Comment

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