1961 5.5 crank and rod assembly

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  • December 4, 2015 at 11:34 am #3106
    1946zephyr
    Participant

      Would a crank and rod assembly from a 1961 5.5 work in a 1955 powerhead?

      December 4, 2015 at 11:43 am #28023
      fleetwin
      Participant

        US Member

        Hmmm, a good question indeed. So, you are trying to update an older engine to a rods with needle bearings? I’m thinking this might work, but have never tried it, hopefully others with more experience will chime in…

        December 4, 2015 at 12:45 pm #28025
        frankr
        Participant

          US MEMBER PAY BY CHECK

          It seems like I tried to do that some many moons ago and it wouldn’t fit. I don’t remember why not, or even my memory is correct. For sure, the needle rods won’t work on the plain bearing crank. Maybe that is what I’m remembering.

          December 4, 2015 at 5:40 pm #28044
          theodore
          Participant

            I posed this question about a year ago, on the old boards. Someone said it will work on my 1957, but you had to grind the crankcase a little so the rod "big end" will clear. I don’t know if a green ’55 is exactly the same as a red ’57 crankcase.

            Poster said it would give you a smoother running engine that would idle even lower than a sleeve bearing style powerhead, if you wanted.

            December 4, 2015 at 9:35 pm #28049
            1946zephyr
            Participant

              Well, fortunately, I’ll be able to test it, because I ‘m going to do a complete tear down anyway. Plus the fact I have a 1961 CD powerhead here too. From what I see, the crank journals are the same, so I may be okay, switching everything out.
              I will keep in mind what Theodore stated about clearances of the rod bolts inside the block. Fortunately, this will be easy enough to check too. From what I can see, the ’55 block is virtually the same as the ’57. Just everything below the powerhead gasket is different.

              December 4, 2015 at 10:12 pm #28053
              theodore
              Participant

                I was going to swap the new style crank, rods, and rod big end needle bearings into the ’57 case. It may not be "rod bolts" that rub, but the rod big end itself. The sleeve bearing crank and the needle bearing crank are two different part numbers, that’s for sure. It could be that the needle bearing setup has a smaller crankshaft journal, and a larger big end casting, to accommodate the needles in between. I haven’t seen it to compare, but that’s (only) my guess.

                December 4, 2015 at 11:25 pm #28059
                dan-in-tn
                Participant

                  US Member

                  Yes it will work as an assy. Crank, rod, etc. I have done it many times. In the last 30 yrs. The parts robbed up through the ’79 6hp will work. You will have to clearance the bottom of the block for the rod caps. Just a little grinding will accomplish this. Makes for a much nicer running motor and does away with one of its worse weaknesses. You still have to run 24/1 because of the wrist pin bushing and brass center main. I am looking for a way to do the 7.5 hp motor now. Comparing all size motors I can find for a solution. The 5.5hp was just easiest first.

                  Dan in TN

                  December 5, 2015 at 1:08 am #28065
                  chris-p
                  Participant

                    I have done it as well. As stated, I rotated the crank slowly, then hit the block with a die grinder where it would hit?

                    December 5, 2015 at 7:19 am #28079
                    1946zephyr
                    Participant

                      Awesome! Thanks bunch guys. I have a rough old cd 12 and I’m goiing to rebuild it bolt for bolt and that is one thing I’m going to improve on it. Plus I ll set it up to take a single line tank.

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