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3 ring pistons

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  • 3 ring pistons

    I've heard of this in the past and might have seen some pictures, but as far as I've been able to find were rings for pistons with 2 grooves and the oil ring. Anybody know where to find rings for a 3 ring piston?

  • #2
    Dennis this is not clear to me. Are you saying you have pistons with 3 compression rings and one oil ring?

    Or just need rings for the traditional 3-groove piston?

    Hastings might be able to help, give them the diameter of the piston and they can usually match up. This is what we just did for the forged pistons we had made for our Stude project. Stock rings we did not want because they are too wide, so we went with narrow ring grooves and Hastings or someone matched our diameter. Be careful, tho, because they have to dig extra deep to find iron rings. For what we got, the top ring from the modern application set was moly, they removed that and substituted iron from other sets.
    Our alloys then were different, and our A motors don't rev high enough to hardly ever seat moly


    • #3
      I was going to call Egge today or in the next few. As you mentioned about rings I'll ask them if they can make a set with thinner rings. I hate to spend a ton of money on this engine, it's .060" already and will most likely need a bore to next size bigger now I'm finding as I progress. I'll know in the next 2 weeks if I'm going to go another direction. The Babbitt looks good in the mains and rods, cylinders aren't scored but camdrive teeth in middle of cam are worn as well the pump drive teeth. I have a regrind cam in a box that has never been used since it was ground so maybe the teeth look better. Who knows, maybe I'll just clean em up and drop em back in. In the picture, piston on the left is from engine I'm working on, piston on the right is from a different engine in the past. Notice how many rings each have.
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      Last edited by Dennis; 08-05-2019, 08:23 PM.


      • #4
        Wow, have never seen a 3-compression ring piston before, and with that width there will be considerable parasitic loss.
        Not sure Egge makes rings

        I'd be looking at Hastings, Grant, or Mahle

        How true are the cylinders? will be fun to seat them if they are oval. Can you access a dial bore gauge.

        When we do a motor job here, even after the machine shop has bored, I always repeat measuring with my dial bore gauge , and mic my pistons, since seldom are all the pistons in a set the exact same diameter. Then I can match the piston to the most appropriate hole to get my .004 clearance, or as close as I can come

        Mic the thickness of the ring and the max ID of the bore they should be able to cross reference something. Then set your ring gaps before installing
        Last edited by tbirdtbird; 08-05-2019, 08:33 PM.


        • #5
          BTW Dennis this is a very interesting case, please keep us informed, Dave


          • #6
            Got the bore gauge. I'm not so sure 3 tight fit rings is a good idea. This engine will be a spare to keep the car running while the good touring engine is down. Not doing any touring with this engine, just around the area to the store costco wallymart home depot etc. The draw to buy it was the head ... it's better than a low compression stocker.
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            • #7
              what was compression before u tore it down?
              Burning oil?
              Maybe leave it as is?


              • #8
                I'm surprised that DaWizard has not chimed in on this thread.
                3 ~ Tudor's
                Henry Ford said
                "It's all nuts and bolts"

                Mitch's Auto Service ctr


                • #9
                  Yeah he never did a follow up on that. This engine has the same brand pistons it appears. I checked all the clearances on all rods and mains, both were close to .002” on everything. Rods had .023” of shims on most, mains had .028”shims. Not that it makes any difference but it is a diamond A block. Previous owner pulled the whole drivetrain out to make a hotrod out of it. This engine has been sitting for quite a few years more like decades. Not a drop of water in the oil pan and no sludge. I have never pulled one of these engines down without a trace of sludge. At least he didn’t sell the parts for scrap. I should have bought the whole shebang but figured this is enough project for now.

                  Tbird, I was thinking same, leave as is. All the valves were ok. Somebody put single lock lifters in it at some time and kept the mushroom stem valves. Valve stems were a bit too loose in the guides. I’m not too keen on the split guides, I have a set of valves with very few miles that were salvaged from another engine. I might use those and press some new guides in. It was not running but when I turned it by hand it felt like good compression in all 4 cylinders.


                  • #10
                    4 ring pistons were used to rebuild engines years ago. I would stick with 3 ring pistons.


                    • #11
                      I saw an ad the other day that Eggs was producing model a pistons with 3 rings and with 4 rings. You have your choice of pistons. FYI


                      • #12
                        I took a ring off one of the pistons to check end gap which looked like an awful lot. Measured bore just about every way imaginable. What I thought was strange was the top of the bore has more wear on the sides where the cylinders are closest together. She's got about .005" at the top and maybe .0005" at the bottom. That's wear beyond what would have been .002" if that's what it had for clearance. The pistons, I popped the rings off one of them and only the oil rings have holes going through. The 3 upper compression rings have no holes in the ring lands. So I might leave that 3rd from the top off. I measured the thickness of the rings compared to a set that were in another set of pistons that have 2 compression rings, thickness the same, so tomorrow I'm going to stop by the store and see if they have a set of .060" over, which is what the bore and pistons are. So I'm a bit puzzled on the cylinder wear because the pistons show no wear on the sides, just where you would expect it to be on the bottom of the skirt where the diameter is bigger. Something I've thought just possible that was not good was the crankshaft was bent .003", so I'm wondering if that could have something to do with it. I have only seen that kind of cylinder wear, a big Cummins diesel that was a 6-1/4" square engine, bore same as stroke, they had the same characteristics of cylinder wear on the side closest to the other cylinder. So beings this is just going to be a short distance running engine I think it'll be just fine without dumping a lot of money into it. Most of the parts I buy for it I will be able to use if I don't put a lot of miles on it, in a different engine. That list of parts will be very small. I have a lot of parts I've kept over the years that will work fine in this engine, never throw anything away that is good. I dug out a camshaft that is supposed to be a touring regrind cam that has a much better set of teeth in the middle for the pump drive, it has never been used since being reground. The pump drive is shot, teeth are severally worn. The top of the block it good, not excellent, but it is good enough it will seal all the way around with no problems. After I got it cleaned up and put the straight edge with a .001" feeler, there was not one bad spot across the cylinders and valves. Length, sideways, crosswise, all good. So tomorrow it's the head and maybe a few other parts. I looked at Vince Falters Ford Garage website on Diamond Blocks, and could not find anything that matched his descriptions as to when it was cast, so it's a mystery to me. There are a lot of letters and numbers cast on it but none of them tell me much. There is one stamp on the top of the block. A few pictures for those who like to look. Any questions or comments, fire away.
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                        • #13
                          I am sure your measurements take into account that the piston diameter is traditionally smaller in the ring area than below the rings.
                          Not sure I have ever seen the pistons themselves wear unless they are scuffed from too tight a clearance, which is not what you are describing
                          Are the 3 comp ring pistons slotted like Henry's originals? I think that is where the .002 clearance number comes from, which as you know is way too tight for a solid piston
                          I think with a bent crank all bets are off.

                          Block sure cleaned up nice!


                          • #14
                            I think the only way you would get wear like that is a bent rod, I would not put that crank back in with out fixing it. There are no short cuts to engine building.


                            • #15
                              George, the crank is now straight. I've straightened a lot of them in the past. What makes it easy on a Model A, only 3 journals. The rods I haven't checked yet. Will do that either late tonight or in the morning.

                              Dave, I measure pistons at the skirt. They don't look to have much wear, still see most of the machine marks on the skirts which are shallow. Measurements taken near the bottom of the bore. Gradually has more wear in the cylinder as I moved towards the top. The most wear area is in the area from the top of where the ring goes down about an inch. If this engine was a touring, I'd get it bored and go .080, but it's just a local runner. It needs to soak in Rust911 for quite awhile and maybe a few times with pressure wash in between. And after that it will be a fight getting it to stop foaming.

                              Yeah I'm never sending a block to someone that sand blast the crankcase. Water jackets maybe but not where there is going to be oil. I've been through that situation and learned my lesson. So I just got the wire wheel and drill out and stripped the outside. You cant leave bare metal laying around even indoors around here or it starts to get rusty.


                              • #16
                                We use oven cleaner on blocks, and when done, we wash it down with ospho to prevent rust. If babbitt is present you cannot do that, then your wire wheel works well
                                You are very correct about not blasting where there will be oil. Sandblasting puts sand places YOU cannot put it.

                                Some neighbor kids (not the sharpest knives in the drawer) sandblasted an oil pan on the inside even tho Miles and I told them not to do that. Their father overrode what we said and commented that we did not know what we were talking about.
                                You know what happened next. That was about the end of the relationship with that family. Ya can't teach unteachable people

                                And we clean water jackets with lye, let it sit in there for a week. You should see the crap that comes out! A section of bowden cable sheath chucked in a portable drill wiggled around all the insides of the jacket doesn't hurt either, especially behind 3 and 4. The water jacket looks freshly cast when done, right down to bare gray cast. Also a problem if babbitt is present, but you can still flush with water and use the bowden sheath
                                Last edited by tbirdtbird; 08-09-2019, 12:25 AM.


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