1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954 - NCRS Discussion Boards

1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

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  • William H.
    Very Frequent User
    • March 1, 1999
    • 249

    1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

    Hello,
    I recently acquired a set of Forged pistons for my 1965 coupe from the son of the original owner. They have a casting number of 3866954. When I got them home I was inspecting them a little closer and noticed that the pins do not slide in and out of the pistons.
    Acording to the 1963 corvette overhaul manual the pins should have from .0005-.001 clearance and when covered with light engine oil should not fall trough the bore.
    I tried to knock one out with a hammer and socket and it did not move. ( I did not apply a lot of pressure because I did not want to distort the piston.)
    I am thinking that maybe there is a small amount of corrosion holding the pins in place. Or maybe they galled the pin bores when removing the rods the last time.
    Than I read a post on another forum where a gentleman had used these pistons and had trouble with the pins fitting and had to hone the pin bores to make them fit.
    This made me wonder if maybe these pistons are different than most press fit piston pins. Could it be that the pin is press fit into the piston and floats in the rod?
    If that is not the case does anyone have any ideas about how to free up the pins? I have applied WD 40 and let it soak overnight but this did not make any difference the pins still wont move.
    Any comments or suggestions would be greatly appreciated.
    Thanks in advance,
    Bill
  • Timothy B.
    Extremely Frequent Poster
    • April 30, 1983
    • 5186

    #2
    Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

    Bill,

    Got to get a micrometer and measure before you start beating on things. If you want to use these pistons get a machine shop to look at them and also measure the skirts.

    Comment

    • William H.
      Very Frequent User
      • March 1, 1999
      • 249

      #3
      Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

      Hi Tim,
      Thanks for the response. I have Micrometers and know how to use them. However I do not have an inside mic that small to measure the pin bore. I guess I'll have to find one. I don't think my dial bore gage goes that small either. I was looking more for someones knowledge of how this engine went together originally to see if it was different than what I was used to. ( Pin pressed into rod and floating in the pin bores) Also maybe somone has an idea about how to best get them apart. Some kind of penetrating oil. Or maybe heating the piston slightly.
      Thanks again,
      Bill

      Comment

      • William H.
        Very Frequent User
        • March 1, 1999
        • 249

        #4
        Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

        P.S.
        Tim,
        You are right I should measure the pistons to see if they are any good anyway. The skirts look good still have oil grooves on them but they could be collapsed and it that case it won't matter about the pins anyway!

        Comment

        • Joe L.
          Beyond Control Poster
          • February 1, 1988
          • 43221

          #5
          Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

          Originally posted by William Holder (31950)
          Hello,
          I recently acquired a set of Forged pistons for my 1965 coupe from the son of the original owner. They have a casting number of 3866954. When I got them home I was inspecting them a little closer and noticed that the pins do not slide in and out of the pistons.
          Acording to the 1963 corvette overhaul manual the pins should have from .0005-.001 clearance and when covered with light engine oil should not fall trough the bore.
          I tried to knock one out with a hammer and socket and it did not move. ( I did not apply a lot of pressure because I did not want to distort the piston.)
          I am thinking that maybe there is a small amount of corrosion holding the pins in place. Or maybe they galled the pin bores when removing the rods the last time.
          Than I read a post on another forum where a gentleman had used these pistons and had trouble with the pins fitting and had to hone the pin bores to make them fit.
          This made me wonder if maybe these pistons are different than most press fit piston pins. Could it be that the pin is press fit into the piston and floats in the rod?
          If that is not the case does anyone have any ideas about how to free up the pins? I have applied WD 40 and let it soak overnight but this did not make any difference the pins still wont move.
          Any comments or suggestions would be greatly appreciated.
          Thanks in advance,
          Bill

          Bill------

          There were VERY few Chevrolet engines which originally used floating pin rods. For 1966, there were NONE. So, assuming the rods are original, there's zero chance that these rods are floating pin type. Also, given the forging number of the pistons, the piston pins should float in these rods. I'd say that corrosion is the cause of the problem you're having. Most likely, it's galvanic corrosion resulting from the dissimilar metals (iron and aluminum) and, most likely, these pistons sat around in a moisture laden environment for quite awhile. Dissimilar metals + water = corrosion.

          How can you get the piston pins out? I'd say it's very possible that you can't without rendering the pistons unusable.
          In Appreciation of John Hinckley

          Comment

          • Loren L.
            Extremely Frequent Poster
            • April 30, 1976
            • 4104

            #6
            Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

            Okay, I'll put on my dumb hat and ask what the objective is here? Are these used or new pistons? Are they std bore or ? Why are you banging on the pins? What can a '63 svc man give you in terms of accurate info on a '65 motor? Aren't you afraid that something MAY have changed?

            Comment

            • William H.
              Very Frequent User
              • March 1, 1999
              • 249

              #7
              Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

              OK joe I think that you are right. I measured the pins and they are exactly what they should be .9270-.9273. as I stated I can't acurately measure the pin bore right now. So I am going to try and find a better penetrating oil and soak them down good for a while. Pistons all meassure real good as far as the diameter so Ill try to salvage them if I can.

              Comment

              • William H.
                Very Frequent User
                • March 1, 1999
                • 249

                #8
                Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                Hi Loren, the objective is to salvage my $100.00. The 63 manual is the only manual except for a suplement for 65. Ill check it to be sure but I don't think they changed anything from 63-65 as the pistons are listed from 62-68. They are standard Bore. So is my engine. I was banging on the pins because I couldn't push tem out with my fingers like you usually can. THe pistons are in really good shape with the exception of the problem with the pins.

                Comment

                • Bob J.
                  Very Frequent User
                  • December 1, 1977
                  • 714

                  #9
                  Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                  I have a quite a few boxes of NOS GM pistons that I bought from closed dealers and the Yunick's shop.
                  Most the time, whatever oil was on the pins has dried up.
                  Once that happens the pin is siezed inside the piston.
                  My advise would be take them to a machine shop.

                  Comment

                  • William H.
                    Very Frequent User
                    • March 1, 1999
                    • 249

                    #10
                    Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                    Hello Bob,
                    what will they do that I cannot? I am afraid they will press them apart and that will gall the pin bores in the piston and ruin them. I think that is what Joe was alluding to when he said there is no way to take them apart without ruining them.
                    I may try to put them in the oven a while and see if maybe the aluminum expands more than the steel pin?

                    Comment

                    • Bob J.
                      Very Frequent User
                      • December 1, 1977
                      • 714

                      #11
                      Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                      William, I really can't answer that not knowing your machine shop or seeing the pistons. Are the pins rusty?
                      You can try the oven, that not be my first choice but obviously pistons with seized pins aren't much use as is.
                      Good luck,Bob J

                      Comment

                      • Steven B.
                        Very Frequent User
                        • April 11, 2012
                        • 233

                        #12
                        Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                        I think you might be onto something if you can apply heat. The trick would be to keep the pins cool while increasing the temperature of the pistons (I would think quickly). As to how much heat, that would be a guess. Someone else may have an idea. Aluminum and aluminum alloys have a low melting point compared to other nonferrous and ferrous metals. You might be able to put them into boiling water for a short period and with the combination of penetrating oil, get them to loosen up. If you have an oxyacetylene torch, a rosebud tip could be used to apply heat relatively evenly. I would expect that you wouldn't want to heat them too much in a small area although aluminum will dissipate heat readily. I would think that if you were to try heating, a few hundred degrees might, and I stress might, work. No guarantees. I'm sure that others might have some thoughts on this. If you do get the pins out, I would suspect that the bores will need to be cleaned up. Good luck.
                        Steve

                        Comment

                        • William H.
                          Very Frequent User
                          • March 1, 1999
                          • 249

                          #13
                          Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                          Just tried to heat in the oven to 250 deg then applied 3 in one oil no luck. I have to go somewhere with the grankids but when I return Im going to try to heat the pistons to 250 again and then canned air on the pin to cool it quickly. we'll see what that does!

                          Comment

                          • Steven B.
                            Very Frequent User
                            • April 11, 2012
                            • 233

                            #14
                            Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                            The quicker you can bring the piston temp up, the less you will have to cool the pins. The pistons will start to lose their heat as soon as the source is removed. Bringing the pins temp down is a good idea. If you could figure out a way to run some cold water through them, you might be able to shock them and get them to loosen up. I believe that you are close to the right heat range. You could be a bit higher without causing problems. Pure aluminum won't melt util 1206 degrees. You have plenty of room.

                            Steve

                            Comment

                            • David S.
                              Infrequent User
                              • March 20, 2014
                              • 3

                              #15
                              Re: 1965 327/350Hp Coupe Pistons Questions about Pin Fit 3866954

                              Pistons don't have to sit around long for the pins to stick. Heat the pin area of the piston with a rosebud and push or bump the pin out. A propane torch may do it but, I always used an oa set. A chunk of aluminum soaks up a lot of heat.

                              Comment

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