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  • Piston ring gap.

    I just went through the whole thread on engines and didn't find an answer, so, what is the end gap of piston rings for the Model A engine?

    I know I have the answer somewhere in my muddled brain but I just can't seem to retrieve it.
    You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

  • #2
    No one has this gap?
    You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

    Comment


    • #3
      Usually the ring manufacturer has a spec listed with the package. We check them at the bottom of the bore

      This was from a Hastings set

      Ring end gap: Top .012" to .015"; Middle .010" to .012";

      Lower .008" to .010"
      3 ~ Tudor's
      Henry Ford said
      "It's all nuts and bolts"


      Mitch's Auto Service ctr

      Comment


      • #4
        Les Andrews, page 1-140. Top ring .012"-.015" Middle ring .010"- .012" Oil ring .008"- .010"
        Measured 1 to 2 inches down the cylinder. Use a piston to push ring in the cylinder so that the ring is square to the cylinder. Measure the rings in the cylinder that they will be installed.

        Comment


        • #5
          Mitch beat me to the punch. Les agrees with Hastings.

          Comment


          • #6
            Thanks, that's what I was looking for.
            You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

            Comment


            • #7
              Just curious, did your ring set come with any specs?
              3 ~ Tudor's
              Henry Ford said
              "It's all nuts and bolts"


              Mitch's Auto Service ctr

              Comment


              • #8
                I haven't opened the box yet.
                You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

                Comment


                • #9
                  Originally posted by Mike Peters View Post
                  Les Andrews, page 1-140. Top ring .012"-.015" Middle ring .010"- .012" Oil ring .008"- .010"
                  Measured 1 to 2 inches down the cylinder. Use a piston to push ring in the cylinder so that the ring is square to the cylinder. Measure the rings in the cylinder that they will be installed.
                  I recently did that and found they came out of the box with a gap of near enough, 0.020". That's more than any specs I have seen but I can't add anything to the rings so I installed them as is. I'm not losing any sleep about them being too tight!

                  Comment


                  • #10
                    It's a catch 22! Which came first, the ring gap or the piston gap?
                    Since the cylinders are bored to provide the proper piston gap first, then the ring gap is what the manufacturer sends.
                    Hopefully not too wide a gap, but what do you do if it is?

                    Comment


                    • #11
                      Originally posted by Tom Wesenberg View Post
                      It's a catch 22! Which came first, the ring gap or the piston gap?
                      Since the cylinders are bored to provide the proper piston gap first, then the ring gap is what the manufacturer sends.
                      Hopefully not too wide a gap, but what do you do if it is?
                      I have assembled a number of engines with gaps I thought were a bit wide and they have been fine. The only way I can see to get the right on spec is to buy a set of rings next size up and gap them yourself. I don't think the $ or the time make it worth while though.

                      Comment


                      • #12
                        Better to be to wide a gap than to small a gap. They sure will tear up the cylinder if to close. I use those gaps as listed. But I also bore the back to cylinders for .004 piston clearance . that gives the rings a wider gap.

                        Comment


                        • #13
                          Well, just so ya know, I have always been of the rule of thumb that +.001 for each inch of bore, and 3.875 is a lot closer to 4" than it is to 3", so all my bores are +.005 -.000. Now, the bore in this block being +.125 will not be 4.004 since the pistons miked out at 3.996 the the bore is 4.001

                          Always has been, always will be!
                          You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

                          Comment


                          • #14
                            I prefer the gap to be on the wide side. But, I also prefer piston clearance to be on the wide side also.

                            Comment


                            • #15
                              If you do not leave at least .004 on the back cylinders they will try to make the bore bigger. Then the piston will lock up or leave funny marks in the bore. Wiz I also use the rule of .001 per inch of bore. Has worked for me for many years.

                              Comment


                              • #16
                                A thou per inch of bore rule of thumb is as old as engines have been about. Why would it change???

                                Comment


                                • #17
                                  The problem builders have is they only see the 3 in 3 7/8 in, not that is only 1/8 inch short of 4 in.
                                  You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

                                  Comment


                                  • #18
                                    Originally posted by DaWizard View Post
                                    Well, just so ya know, I have always been of the rule of thumb that +.001 for each inch of bore, and 3.875 is a lot closer to 4" than it is to 3", so all my bores are +.005 -.000. Now, the bore in this block being +.125 will not be 4.004 since the pistons miked out at 3.996 the the bore is 4.001

                                    Always has been, always will be!
                                    .003" too .004" per inch of bore...for the top ring...UNLESS it has Hypereutectic pistons, then it's more.

                                    Comment

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