Home Forum Ask A Member 1966 FD 20 troubles

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  • #31890
    Mumbles
    Participant
      quote wannabe outboard guy:

      Mumbles, are you running J 4 or J 6 plugs in your FD’s?

      Neither. If the motor is being run hard, which I usually do, I go with the colder NGK B8S (J 4) and go from there. If the motor is being babied or it’s worn a bit and with lower compression, the slightly hotter NGK B6S (J 6) work well.

      As far as your motor goes, I’d attempt to save it. As long as the cylinder isn’t gouged above the ports, it should make good compression with a new set of rings and possibly a replacement piston.

      #31894
      wiscoboater
      Participant

        The cylinder looks great above the ports. For my own educational purposes I think I might try that Mumbles. I’ve done lots of ring jobs on small block Chevys and Fords. Yet to do it on one of my outboards. It’s 2 degrees outside today so good quality basement shop time where it’s warm seems like a good idea to me.

        #31897
        fleetwin
        Participant

          US Member

          Looks too nice to scrap that powerhead. I’m with Mumbles, clean up the cylinder, find a decent used/new piston and rings, and off you go with a nice original engine. Those exhaust cover screws came out without a fight, so it must be a clean fresh water engine. I’m assuming you have had some OMC powerhead experience, so this job isn’t a big deal. Like others have said, be sure to measure the cylinder after cleaning it up, and don’t worry about removing every little scratch or gouge. Remember that honing the cylinder is really boring the cylinder, just at a much slower rate. I would prefer to have an imperfect (little scratches/gouges) cylinder that is still in tolerance (not out of round/oversize), than a clean cylinder that has been honed to oversize….Using the ball hone helps reach all the little imperfections.
          You will know better what you have once it is apart and you have cleaned up the cylinder so it can be properly measured.

          #31911
          SCOTT MEYER
          Participant

            From your description I’m suprised the cylinder survived. I’d be wondering what got sucked in there and caused that damage.

            #31925
            wiscoboater
            Participant

              I don’t know scotty. I’ll post some pics of the piston and rings when I get it out. Whatever it was, I’m suspecting a piece of ring or ring land, it sure left a good gouge. I just ordered a NOS set of rings off Ebay for $25. Will start the tear down tomorrow.

              #31933
              SCOTT MEYER
              Participant

                10 years ago when I was starting out in this hobby I bought this ’57 Bigtwin with low compression in one cylinder. The wrist pin bearing was beat to death. The needles got loose and this was the result.
                On this one the cylinder was scored beyond saving.
                Now the FD is a completely different motor and I’m not saying that is your case, but something to look out for if your planning to rebuild.

                #31950
                frankr
                Participant

                  US MEMBER PAY BY CHECK

                  Ah yes, the 1957 Big Twin wrist pin needle bearings. You certainly weren’t the only one finding the weakness. Nope, those needle bearings were long gone extinct by 1966.

                  #31975
                  wiscoboater
                  Participant

                    Well, here’s the carnage. What ever got into the cylinder must have been a piece of aluminum. It tore up the side of the piston a bit and seems to have melted and fused it’s self to the cylinder wall. It got into the ring lands and locked the rings in place. What I thought was a gouge in the cylinder wall was actually a raised ridge on the cylinder wall. It was whatever got caught in there. It came off with a little sanding with some emory cloth and the cylinder looks like new yet, no scratch or gouge at all. With a new piston and rings I think this motor might be good as new.

                    #31979
                    chris-p
                    Participant

                      Hey thats great news really.

                      #31982
                      Mumbles
                      Participant

                        At least you can save the block! 😀 Pistons are a lot easier to find and replace. The ridge you had on the cylinder wall would have been aluminum transferred over from the piston. Some guys use muriatic acid to remove it as the acid will quickly destroy the aluminum without harming the cast iron cylinder.

                        The guy that owned this six horse motor missed one needle bearing and dropped it in the motor while putting it back together. He got about three minutes of run time out of it before he realised something wasn’t right.


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