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Piston: K20A3 vs. F23A?

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    Piston: K20A3 vs. F23A?

    Working on a F22A1 spare block, which has been oversized to 85.5mm. Found the cylinders has minor scorings. I can feel one of those lines by my finger.

    I am debating myself whether to go with,,,,
    1) Hone and re-ring.
    2) Oversize to 86mm and use K20A3 pistons with minor machine work.
    3) Oversize to 86mm and use F23A? pistons and longer connecting rods from eBay.

    Budget is tight. I may give-up this car when the engine is installed, to my son who has gotten his drivers license a few weeks ago. It will never see turbo.





    What are your thoughts?
    Last edited by oyajicool; 05-21-2013, 12:47 PM.
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    #2
    The dish of the F23A piston is a little smaller and the bore is 1mm larger than the F22A piston. This would usually make for a slight bump in compression, but since your ne compression height is 30mm instead of 30.55mm you're back to where you started at 8.8:1. For tuning purposes (i.e., avoiding them) that may be a good option. I even have a set I don't need.

    The K20A3 piston has never been a favorite of mine. The swirl pot on top is just too weird for me. Sure, it would bump compression up a bit because it's only a -2.5cc dish (10.1:1 neighborhood) but I don't know what tuning issues that piston face would cause. Maybe nothing and I'm just leery because it's the unknown.
    My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

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      #3
      That .5mm deficit on F23A pistons can be compensated by having after market rods which are claiming to have 142mm in length, no?

      I also should mention that I have Bisi stg2 cam, adjustable cam gear, balance shaft eliminator kit, A6 intake assembly and P28(need chipped and tuned). All of these may go on this build, pending that I would be able to afford another car for my son. So, that I will be driving this one.

      +++++++++++++++++++++++++++++++++++
      There are new F23A pistons and rings available for $99.99 on eBay.
      +++++++++++++++++++++++++++++++++++
      Used K20A3 pistons are also available with similar price, but no rings.
      Last edited by oyajicool; 05-21-2013, 01:54 PM. Reason: misspell
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        #4
        I've seen some advertised as 142mm and others at 141.75mm. I'm inclined to believe the 141.5mm as it's more precise. But in machined lengths, simply being inclined to believe is a recipe for failure. We won't know until someone who has ordered them measures them.

        Assuming they're 141.75mm then you're looking at 9.0:1. If they're in fact 142mm then you'll be closer to 9.1:1. Not a huge difference, but something. Maybe good enough for 1 ft-lb of torque in the lower rpm range.

        You could mill .030" combined off the head and deck to bump you up closer to 9.8:1 and require a tune similar to the PT4 ECU's. But in order for us to get that .bin file I'm going to have to stop being a lazy ass and mail the PT4 to Anthony (cloadasc) for him to read it.
        My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

        Comment


          #5
          Give him the K20 slugs and lie to him and tell it's all stock.


          On a serious note I've always been curious about tuning issues when raising compression, obviously it's the safest route to go, but my eventual build will be on the fly and a budget as well so I've always been scared about riding long term with no tune....well at least a tune that doesn't match the new compression, my current tune is for the 10.6:1.
          Last edited by Joey GT-R; 05-21-2013, 01:37 PM.
          '94 JDM H22A: 178whp 146wtq

          Originally posted by deevergote
          If you say double dutch rudder, i'm banning you...

          Comment


            #6
            Another question,,,,,,

            What do you think the cause of that area circled "Not OK" in that photo?
            Twisted/bent rod?

            I'd like to inspect the rods.
            How can I separate the rod from piston?
            Do I need to heat them up in oven and arbor press them out?

            Thank you,,,

            +++++++++++++++++++++++++++++++++++++

            Did some looking around on the internet and found that hydraulic press is used along with dies.
            Since I am thinking of getting another set of pistons, I think it is better off to purchase new set of rods instead of taking time to inspect existing ones.
            Last edited by oyajicool; 05-27-2013, 01:01 PM.
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            Comment


              #7
              Did it get overheated? Piston ring end gap too tight?
              "Brought to you by Carls Jr."

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                #8
                No detailed information was given when I bought this other than saying it was build by a shop (I forgot the name). The engine was removed with about 500 miles.

                I think oil leak issue was one of reasons for removal. I have found that front seal was not installed properly.
                Last edited by oyajicool; 05-27-2013, 09:52 AM.
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                  #9
                  Piston assembly weights

                  K20A3 (a retainer is on the scale, not visible)


                  F23A


                  No rings are included. K20A3 pistons are more advantageous than F23A pistons.

                  F22A1, OS 0.5mm (I think this is an aftermarket piston)


                  ++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++
                  Side note

                  F22A1 Connecting rod


                  K20A3 Connecting rod


                  K20A3 rod has tremendous weight advantage over F22A1 rod. But, they are not compatible with F22 block/crank.

                  F22A1 aftermarket rod
                  Last edited by oyajicool; 06-07-2013, 03:00 PM.
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                    #10
                    Originally posted by oyajicool View Post
                    Working on a F22A1 spare block, which has been oversized to 85.5mm. Found the cylinders has minor scorings. I can feel one of those lines by my finger.

                    I am debating myself whether to go with,,,,
                    1) Hone and re-ring.
                    2) Oversize to 86mm and use K20A3 pistons with minor machine work.
                    3) Oversize to 86mm and use F23A? pistons and longer connecting rods from eBay.

                    Budget is tight. I may give-up this car when the engine is installed, to my son who has gotten his drivers license a few weeks ago. It will never see turbo.





                    What are your thoughts?
                    Build it with your son, if you can? I wish I had a dad to build my car with. Sadly hes an alcoholic meth head and I haven't seen him in years.. But, hey, you can't win them all. Try to win him over with cool pics of modified cb7's!! They are really great looking Honda's.
                    Originally posted by Quashish
                    hahaha

                    noobs be like where to be buying hella flush yo?

                    Comment


                      #11
                      Sorry to hear about your father. I don't wanna go in detail telling 'bout it but I do know it is almost impossible to get that shit out of one's system.

                      We did another engine build a few years back on an EF Civic. I gave it up to my first son who is currently driving it in Delaware.
                      The son I was referring in the first place on this thread is the second son. He should be coming up to the shop and help me on the work. But, it is not happening,,,,,,yet.

                      ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++
                      7/15/2013
                      This engine build is taking back seat due to lack of time and funding at the moment.
                      Measured the length of aftermarket connecting rod the other day.
                      It was 142mm.
                      So CR should go up by a hair by using F23A1 piston and aftermarket rod.
                      Last edited by oyajicool; 07-15-2013, 08:02 AM.
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