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  • peeeot
    Experienced
    • Oct 23 2005
    • 437

    Blow by.

    Long time, no post! I haven't been messing with the old bird much over the past several months.

    Even with a pcv valve, my engine is producing enough blow-by that at idle when everything's warmed up I will see gases coming out of the hood scoop. Compression is around 150 psi or so. I've been doing some reading on engine break-in and suspect that my engine saw too much low-speed, low-load operation since the installation of new rings, resulting in improper ring seating. Maybe the cylinder walls are glazed, I dunno. Does anyone have suggestions for how I might go about remedying this issue? Any hope for a proper ring break-in? What about products like engine restore?

    Aside from the blow-by, the engine's performance is quite satisfactory.
  • Guest

    #2
    You might want to install Positive Crankcase Ventilation,it is very simple on this web site go to techincal page and you can see how to do it,I dont know if Alexander sells the adapter to do this if not John Dexter at the thunerbird ranch does sell the needed parts

    Comment

    • JohnG
      John
      • Jul 28 2003
      • 2341

      #3
      Three questions:

      * how many miles on your motor since you rebuilt it?
      * what type of rings? (cast iron or chrome moly)
      * what weight and type of oil?

      You could squirt some oil in the cylinders and retry the compression test - this would tell you if it was the rings or not.

      john
      1958 Hardtop
      #8452 TBird Registry
      http://tbird.info/registry/DataSheet...r~equals~8452)

      photo: http://www.squarebirds.org/users/joh...d_June2009.jpg
      history:
      http://www.squarebirds.org/users/johng/OCC.htm

      Comment

      • peeeot
        Experienced
        • Oct 23 2005
        • 437

        #4
        Not many miles. Less than 1000, I'd say offhand. But since the car wasn't legal and there were transmission issues when I first rebuilt it, most of the running it did early on was idling and low-speed (less than 40 mph) trolling around the neighborhood. The rings were cast iron, if I'm not mistaken. Oil is 10w30. I tried the oil squirt months ago and compression immediately jumped to 180 where I tested it. What I'm wondering is, did I somehow put in the wrong rings, have they failed to seat, and is there anything I can do about the present situation short of taking the engine apart again?

        Comment

        • Alexander
          Webmaster
          • Oct 30 2002
          • 3321

          #5
          I have been travelling at low speeds in my neighborhood for four years on a rebuilt 352 engine in my 1960 Golde Top. I have never had it at highway speeds. I rarely drive it at more than 20 mph. It had no blow by ever. I used regular engine oil initially and changed to synthetic after the first oil change. The only difference over the years that I have noticed its that the engine runs smoother.

          There is something wrong with your rebuild with either your compression or your oil rings. You should not get the blow by you describe no matter how you break in your engine.
          Alexander
          1959 Hard Top
          1960 Golde Top
          sigpic

          Comment

          • JohnG
            John
            • Jul 28 2003
            • 2341

            #6
            major question: did you use new pistons???

            If so, ignore the rest. If not then you have the possibility that the grooves in the pistons are worn vertically and gas and oil are going around the ring. The clearance between the ring and the groove is only on the order of .002" or so in a new motor.

            I also forgot to ask if the oil was synthetic - I will assume not. Synthetic would not be conducive to seating rings.

            Do you know what grit the hone was done to??

            I rebuilt my motor a couple of winters ago. The blow by ceased in about 40-50 miles even though the compression rings were chome moly and certainly not worn in that quickly.

            Assuming the honing was decent and the pistons new, engine people tell me you need to get the motor up to temp and put some stress on it such as at highway speed. Steve Christ's book has some guidelines for engine break-in as well which I could scan in and email to you.

            Frustrating!!!!

            john
            1958 Hardtop
            #8452 TBird Registry
            http://tbird.info/registry/DataSheet...r~equals~8452)

            photo: http://www.squarebirds.org/users/joh...d_June2009.jpg
            history:
            http://www.squarebirds.org/users/johng/OCC.htm

            Comment

            • Guest

              #7
              Agree-the rings are your problem,they do need some varied RPM for break-in. Watch what oil you use. That is too much blow-by for too long. Nail it a couple of times and let it come down from speed by itself, but don't run at a continuous speed for long periods. If they don't seat-in you have no choice but to tear it down, bummer!!

              Comment

              • peeeot
                Experienced
                • Oct 23 2005
                • 437

                #8
                I should make a clarification. I only see the blowby coming out of the hood scoop after I've been driving at sustained speeds for a while and then come to a traffic light or stop sign or something. If the car is just idling in the driveway, the pcv valve seems to be able to handle that amount of blowby just fine.

                I did some varied highway dirving today, getting more aggressive with the throttle than I normally do then letting the car coast back down to below the speed limit. It handled it fine. I haven't driven enough since to tell whether that affected anything.

                The pistons were not replaced. Someone had been through that engine before me; it showed evidence inside of previous machine work with little wear. I honed the cylinders with a standard three-prong hone like you get at the parts store.

                I retained the box from the rings I installed. As far as I can tell based on the part number, they are standard size rings. What I can't recall is whether I made certain to measure cylinder diameter. It seems possible that I could have installed standard rings in cylinders bored .030 over, but that would be more careless than I give myself credit for... I didn't have any work done on the block except to install cam bearings but I know the crank was machined down such that I had to use .010 oversize main and rod bearings.

                Comment

                • JohnG
                  John
                  • Jul 28 2003
                  • 2341

                  #9
                  the fumes out of the hood scooop are probably coming from the oil filler cap, which does breathe. If you look at the underside of the hood in that area you may find film from fumes.

                  I guess the key question from me would be: did you use a feeler gauge and measure the vertical clearance between the rings and the piston groove??

                  Do you still have the old rings you took out???
                  1958 Hardtop
                  #8452 TBird Registry
                  http://tbird.info/registry/DataSheet...r~equals~8452)

                  photo: http://www.squarebirds.org/users/joh...d_June2009.jpg
                  history:
                  http://www.squarebirds.org/users/johng/OCC.htm

                  Comment

                  • Alexander
                    Webmaster
                    • Oct 30 2002
                    • 3321

                    #10
                    If you have oil fumes coming out of the oil breather cap at idle, the screen at the back of the manifold may be clogged with oil and dirt. I don't know if you cleaned it out when you did the rebuild. It is rectangular, but you can get it outwith forceps through the blow by pipe hole with engine still in the car.
                    Alexander
                    1959 Hard Top
                    1960 Golde Top
                    sigpic

                    Comment

                    • bcomo
                      Super-Experienced
                      • Sep 23 2005
                      • 1223

                      #11
                      Is that screen at the back of the manifold a 352 item, or is that part of the road draft tube?

                      Do I need to do any maintenence like that on a 430. I don't see that listed in the shop manual.
                      Bart
                      1960 Hard Top/430
                      Thunderbird Registry Number 1231

                      Comment

                      • Alexander
                        Webmaster
                        • Oct 30 2002
                        • 3321

                        #12
                        The screen is inside the manifold. It is access via the blowby pipe hole. The 430 most probably has this also.
                        Alexander
                        1959 Hard Top
                        1960 Golde Top
                        sigpic

                        Comment

                        • byersmtrco
                          Super-Experienced
                          • Sep 28 2004
                          • 1839

                          #13
                          Check the int manif. Poss crack? Then check your valve guide seals. After that, I would suspect ring break in was not made.
                          Maybe they never seated.

                          I run a supliment. It's a GM product called engine oil supl. It's GM part # 1052367.The proof in the pudding was my 72 El Camino that went 243K on the orig eng. I ran that all along. They might be pulling it from the market (EPA reasons only, like top eng cleaner)
                          It's great for break in.
                          It may still be possible to get your rings to seat.

                          This was my break in procedure. Up to 50 miles, below 50 mph. No more than qtr throttle. Changed oil @ 500. 4 qts of 10/30 & one eng oil supl. Drove country roads mostly btwn 40 & 60 mph up to 300 miles. 3-5 hundred, varied speed, but kept it under 70. Got on it a little, say 1/2 throttle, but shut off at 70. Varying the speed helps accel then decel, never kept a steady speed. Figured ok for road trip @ 500 (freeway speed, but still varied (65-75-70-65) Kind of annoying but worked. I'm at aprox 2000 miles on the new motor. No oil consumption btwn oil changes and no blow by. I do have the 62 style PCV hooked up. Even the air filter element is clean where the hose from the oil cap dumps in.
                          She runs like a scalded cat too. The rear diff is 300's, not 310's (been that way for years(decades). So she's got some long ol' legs.
                          You better have something with big hairy ones to go by that Ford from 70-100 !!!

                          I know that's more than .02, But main point is Take it out and Run It !!!!!

                          Comment

                          • JohnG
                            John
                            • Jul 28 2003
                            • 2341

                            #14
                            John, my break-in was almost identical to yours with the same kind of results. It works!!

                            When Pete said his compression came up to 180 when he squirted oil in the cylinders, that got my attention as indicating the rings have some kind of problem.

                            I rebuilt a 4 cylinder motor cycle engine a few years ago -all new parts. After 1000 miles the compression was still low and there was some oil consumption. I had been running it on 20W-50 (common for air cooled bikes). I ran it on 10W-30 for 500 miles and the rings finished breaking in. Compression went up and other problems went away. Lesson learned!

                            john
                            1958 Hardtop
                            #8452 TBird Registry
                            http://tbird.info/registry/DataSheet...r~equals~8452)

                            photo: http://www.squarebirds.org/users/joh...d_June2009.jpg
                            history:
                            http://www.squarebirds.org/users/johng/OCC.htm

                            Comment

                            • peeeot
                              Experienced
                              • Oct 23 2005
                              • 437

                              #15
                              So I'm driving my car daily now, and I have some more information and detail. First off, highway cruising really loads the engine up with blowby. If I have the a/c vents open, the blowby is visible as it enters the passenger compartment (clearly it isn't sealing properly in the engine compartment). After driving on the highway is when the blowby out the hood scoop is the worst (and it is indeed coming out of the oil filler). BUT. If, at idle at a stoplight, I put the car in park or neutral, the blowby stops coming out, which (I suppose) means the pcv valve is sucking it strongly from the other side at fast idle. I cleaned the intake manifold thoroughly when I had the engine apart. I don't remember any screens, but there was a flat metal panel stuck to the underside beneath the road draft tube hole.

                              I really don't know whether ring seating is the issue. It seems like if I put in the wrong rings, adding heavy weight oil would not have caused the jump to normal compression. I added a can of Engine Restore yesterday in the hopes that it would help the rings seal better and improve compression/reduce blowby.

                              I haven't retained my old rings, but I think I did check the clearance between the new rings and their channels in the pistons. I wouldn't have reused the pistons if I checked it and it was out of spec.

                              Comment

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