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  • Eric S

    • Jun 10 2018
    • 1046

    Flywheel to block alignment

    Checking an engine, I measured back of flywheel to rear o f block and I noticed a difference of around .060", left to right.
    Turned the engine 180 and difference remained but the small gap went from one side to the other
    Looks like the flywheel is slightly bent.
    Now it's.060" but I have no idea if it means anything, if it's too much or within tolerance?
    Engine was running fine and don't want to fix what isn't broken ..
  • simplyconnected
    Administrator
    • May 26 2009
    • 8727

    #2
    The flex plate should run true. Since a flywheel is machined, it should run even truer. I can't think of anything that would bend a flex plate. It is possible that some kind of 'junk', like rust, was not cleaned off the crankshaft before the flex plate was installed.

    A few thou at the center will be more drastic five inches out. I'm more concerned about the pressure plate or torque converter that bolts to the flywheel or flex plate. Can you feel a shake with increased RPM?
    Member, Sons of the American Revolution

    CLICK HERE to see my custom hydraulic roller 390 FE build.

    "We've got to pause and ask ourselves: How much clean air do we need?"
    --Lee Iacocca

    From: Royal Oak, Michigan

    Comment

    • Eric S

      • Jun 10 2018
      • 1046

      #3
      No shake, all was running fine.
      What is the difference between a flywheel and a flexplate?
      Does removing the plate to check and clean the surfaces involve anything else than removing a few bolts and reinstall?

      Comment

      • simplyconnected
        Administrator
        • May 26 2009
        • 8727

        #4
        Originally posted by Eric S
        No shake, all was running fine.
        What is the difference between a flywheel and a flexplate?
        Does removing the plate to check and clean the surfaces involve anything else than removing a few bolts and reinstall?
        A flexplate and a flywheel both have the starter ring gear. That's the only thing they have in common.

        A flexplate is used for automatic transmissions to mount the torque converter.
        Manual transmissions have a clutch with a pressure plate that bolts to the flywheel.

        Removing the flexplate or flywheel requires the transmission (and driveshaft) to be disconnected just to get to the crankshaft bolts. Usually, the exhaust pipes must be removed first.
        It's not an easy or quick task. - Dave

        Member, Sons of the American Revolution

        CLICK HERE to see my custom hydraulic roller 390 FE build.

        "We've got to pause and ask ourselves: How much clean air do we need?"
        --Lee Iacocca

        From: Royal Oak, Michigan

        Comment

        • Eric S

          • Jun 10 2018
          • 1046

          #5
          Well the engine is hanging on my engine stand....

          Comment

          • simplyconnected
            Administrator
            • May 26 2009
            • 8727

            #6
            Eric, you don't say whether you have a stick or automatic. In either case, unbolt the flex plate or flywheel and clean the mating faces of the crank flange and flywheel. Then re-assemble and check the runout again.

            If your engine is on a stand, then you really don't know if it vibrates.
            Member, Sons of the American Revolution

            CLICK HERE to see my custom hydraulic roller 390 FE build.

            "We've got to pause and ask ourselves: How much clean air do we need?"
            --Lee Iacocca

            From: Royal Oak, Michigan

            Comment

            • Eric S

              • Jun 10 2018
              • 1046

              #7
              It's an automatic.
              engine was running in the car and running fine. As I said before I don't want to fix what is not broken.
              Will pull off the flexplate and check.
              Another concern though.
              I had to replace the flywheel on my Cobra's FE and it is sturdily screwed mon the engine.
              On this small block, the flexplate is also well locked but the torque converter is held by just 3 screws and 3 small mounting tabs. This seems to be a light connection between engine and gear box. I know it works but makes me wonder ...
              Last edited by Eric S; August 27, 2022, 06:59 AM.

              Comment

              • simplyconnected
                Administrator
                • May 26 2009
                • 8727

                #8
                Originally posted by Eric S
                ...I had to replace the flywheel on my Cobra's FE and it is sturdily screwed mon the engine.
                On this small block, the flexplate is also well locked but the torque converter is held by just 3 screws and 3 small mounting tabs...
                FE crankshafts use six bolts like this, including the reinforcement ring:

                DSCN6990.jpg
                What small block engine are you referring to? I've never seen torque converter mounting with fewer than FOUR studs and nuts, like this:

                DSCN6988[1].jpg

                What do you mean by, '3 small mounting tabs'?
                Do you have pictures? - Dave

                Member, Sons of the American Revolution

                CLICK HERE to see my custom hydraulic roller 390 FE build.

                "We've got to pause and ask ourselves: How much clean air do we need?"
                --Lee Iacocca

                From: Royal Oak, Michigan

                Comment

                • Eric S

                  • Jun 10 2018
                  • 1046

                  #9
                  My engine is not a Ford
                  Or imagine a Mustang going to a party and wearing a bowtie.
                  But 3 or 4 bolts seems not too much.
                  They are mounted farther apart and the longer radius means less torque. Anyway it worked for decades so it should be enough...

                  Comment

                  • simplyconnected
                    Administrator
                    • May 26 2009
                    • 8727

                    #10
                    Eric, it's customary to let us know exactly what engine we're talking about.
                    No wonder there aren't any pics.
                    Member, Sons of the American Revolution

                    CLICK HERE to see my custom hydraulic roller 390 FE build.

                    "We've got to pause and ask ourselves: How much clean air do we need?"
                    --Lee Iacocca

                    From: Royal Oak, Michigan

                    Comment

                    • Eric S

                      • Jun 10 2018
                      • 1046

                      #11
                      I asked generic questions that may apply to any engine, I guess.
                      I didn't want to step in asking "what do you think about my Chevy engine" here.
                      Didn't wanted to hide anything either.
                      Sorry if I hurt you. Wasn't intended, really, and we all appreciate your expertise, time, dedication and help.
                      As for the pics, it's just I didn't have them available.
                      Now do we have a space on this forum for non Ford topics?
                      Is it tolerated at all (I should have asked first)?

                      Comment

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