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  • Engine: piston ring check with head off

    Is there a good way to check piston rings on a six cylinder with the head off the engine? I am having the head checked and worked and while it is in the shop I thought their might be some witchcraft way out there to check the piston rings for leaks, etc.

    Thanks in advance,
    gregor

  • #2
    No good way. But you are more than halfway to doing the job right.
    Keep going.
    HTIH (Hope The Info Helps)

    Jeff


    Get your facts first, and then you can distort them as much as you please. Mark Twain



    Note: SDC# 070190 (and earlier...)

    Comment


    • #3
      Odd vertical grooves in the cylinder wall can indicate a broken ring--cracked piston.

      Comment


      • #4
        Take a look at the ridge in the cylinder where the top ring stops. It should be at most a couple of thousandths, about enough to catch a fingernail on. The larger the ridge, the more likely the rings need to be replaced. Look for any scores in the cylinder wall. There may be some streaks where the gaps in the rings occur, but you should not be able to feel a groove. Look for any crosshatching in the cylinder walls. If you see crosshatching, it is a sure sign that he rings are still good, but the absence of crosshatching does not mean that the rings are bad.

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        • #5
          Did you check compression before removing head? yes-good or bad? No-
          Was there a skip on any cylinders? Yes-which ones? No
          Was any cylinders wet with oil? Yes-all or one? No
          Was any plugs fouled? Yes-How many? No
          Was it using oil? Yes- How much? No
          No witchcraft will do this. If your first answer is Yes-Good, and the last four are no, Button it up. If any of the last 4 are Yes, Then roll the dice.



          Was it using oil?

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          • #6
            Gregor -

            The basic answer is no. There is no meaningfull way of checking anything about the rings at this point.
            But I'd be willing to bet that even IF...the actual ring seal is still good in all six holes, the end gap is WAY too large. This in itself is a big compression leak...blow-by maker.
            Actual compression numbers aside, I'd say your (from your light description) leakdown numbers are somewhere near 20%/25%. This isn't a good thing..!

            Mike

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            • #7
              I agree with Mike in post 6 and DEEPNHOCK in post 2. At this point it's a good idea to do them now and save yourself from having to do anything else for quite awhile. It will be a good time to see how the bottom end is doing as well.

              Comment


              • #8
                THANKS FOR ALL YOU INPUTS, I APPREICATE THEM. Now on to the next, bigger problem (I think). I am inspecting the cylinder walls and find on one of them about an inch and 1/4 down from the top, a damaged "scuff" mark for lack of a better term. I know you will ask me how deep, etc but I don't know due to lack of tools but it is deep in my mind since I have always been told that they should be smooth as a baby's bottom, etc.
                Question: There are no rough edges on this scuff but it is deep. Is it possible to get away with doing nothing here or not? Fingers crossed..... Thanks again,
                Gregor

                Comment


                • #9
                  If it catches your finger nail as you run it across the mark (both directions)....it sounds like it's time for a rebuild.

                  If you like this car and plan on keeping it...don't shortcut the proper process, save if you have to and do it right.

                  Mike

                  Comment


                  • #10
                    Gregor,

                    Do you have a digital camera? If not, do you have a smart phone with camera? Take a picture, save it as a JPEG file on your computer and then post it here. If you don't know how to post pictures here we can help you figure it out.

                    Only one cylinder with this anomaly; and it being about 1-1/4 inch down from the top? That doesn't sound good. Is that scuff in line with the centerline of the block or is it on one side?
                    Last edited by hausdok; 12-30-2013, 01:04 PM.
                    Mike O'Handley, Cat Herder Third Class
                    Kenmore, Washington
                    hausdok@msn.com

                    '58 Packard Hawk
                    '05 Subaru Baja Turbo
                    '71 Toyota Crown Coupe
                    '69 Pontiac Firebird
                    (What is it with me and discontinued/orphan cars?)

                    Comment


                    • #11
                      For your original question.. No!

                      As noted an initial compression check (with the head on) would have been the best triage for the engine.

                      Crank and check compression and note number.. Squirt a couple shots of oil in the spark-plug and try again. If the numbers go up drastically, then it's good indication rings are week.

                      If the number stay the same and the compression is low, then it would point to the valves.

                      A secondary leak down test with a differential compression tool would be next. Pumping air into the cylinder will also give you a chance to hear which valve is leaking..

                      Comment


                      • #12
                        Cylinder wall finish technology per Chrysler ca: 1947
                        http://www.imperialclub.com/Repair/L...002/page18.htm

                        Comment


                        • #13
                          Old Tech.

                          Originally posted by Dan Timberlake View Post
                          Cylinder wall finish technology per Chrysler ca: 1947
                          http://www.imperialclub.com/Repair/L...002/page18.htm
                          Wow, that there is some really old Chrysler Specific Tech. that should be ignored.

                          I am pretty sure, that technique was long abandoned for a REASON!
                          StudeRich
                          Second Generation Stude Driver,
                          Proud '54 Starliner Owner
                          SDC Member Since 1967

                          Comment


                          • #14
                            I probably should have been more specific on the relevant part of the Chrysler spec.
                            "On the other hand, if the cylinders are scuffed....... they'll have to be smoothed out before new rings are installed." I was surprised I was unable to easily find some pix to help define "scuff."

                            Stepping thru the rest of the doc has some stuff I think is still pretty useful.
                            p16 - Checking ring side clearance/groove clearance in pistons.
                            p15 - cartoon with caption that would likely prove fatal in real life

                            Comment


                            • #15
                              Originally posted by Gregor View Post
                              THANKS FOR ALL YOU INPUTS, I APPREICATE THEM. Now on to the next, bigger problem (I think). I am inspecting the cylinder walls and find on one of them about an inch and 1/4 down from the top, a damaged "scuff" mark for lack of a better term. I know you will ask me how deep, etc but I don't know due to lack of tools but it is deep in my mind since I have always been told that they should be smooth as a baby's bottom, etc.
                              Question: There are no rough edges on this scuff but it is deep. Is it possible to get away with doing nothing here or not? Fingers crossed..... Thanks again,
                              Gregor
                              Depending on where the scuff mark is, it could be a loose wrist pin at that distance from the top.
                              When I got my Champion running after it had set in storage for 12 years it smoked a fair bit. I pulled the head off and the cylinder walls looked pretty good until I rolled it over a bit. The back cylinder had a score about 3/4" wide or so and quite deep starting about that same distance from the top. Turned out the bolt holding the wrist pin in the rod was loose and the pin had gouged up the cylinder wall. I had to get that cylinder sleeved so make sure you check that engine further before you have more damage.
                              Nick

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