Releasing stuck valves and cylinder leak down

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  • Marty_B
    Senior Member
    • Feb 2023
    • 32

    Releasing stuck valves and cylinder leak down

    Hi Everyone,
    I finally got the head off of my motor and have two questions. The first is I have 4 stuck valves. They are STUCK! How does one get the valves unstuck without damaging anything?
    Next? I rotated the engine until the cylinders were pretty much at the same level and put about 1/8 of an inch of 30w oil in each cylinder. The next day, about 90% of the oil leaked out of #3 and after about 3 days, most of the oil had leaked out of #2 and #3. #1 and #4 have no noticeable leakage. How bad is this? I wasn't able to do a compression test before I got the head off due to the stuck valves. The cylinder sleeves don't look too bad but I am trying to decide how far I go in this repair. What are your thoughts?

    Thanks!
    Attached Files
    Last edited by Marty_B; 06-27-2023, 06:08 PM.
  • Dave Neptune
    Afourian MVP, Professor Emeritus
    • Jan 2007
    • 5099

    #2
    When rotating the engine you can open the valves. On each valve stem when open give a little spritz of penetrating oil or something like Tri-Flo. The Tri-Flo is a thin oil with silicone in it an lubricates well and penetrates a bit. Let the oil or penetrating oil sit for a while to work. Rotating the engine will help, you can even use the starter.
    After the oil has had some time to work bring the engine to TDC on the compression stroke of of the cylinder with a stuck valve. The valve will remain open and on compression the lifter & valve will be off the camshaft because it is stuck open. Now get a wooden dowel around 5/16 ~ 3/8 of an inch, note dowels are a hard wood. Place the dowel in the "center" of the valve and give it a tap with a light hammer. Strike it lightly a few times and it should move or pop closed because it does have valve spring pressure trying to close it. Repeat as necessary and you can increase your striking force slowly until you get them worked loose ~ patience ~ patience.

    As far as the oil leaking down you may have stuck rings. Rings will almost always come loose once the engine is running with some top oil in the fuel. Add an ounce or so of MMO to the leaking cylinders as MMO does penetrate a bit just to get some oil where they are sticking while you have the head off. The rings will not "un-stick or rarely do" until the engine is running. Mix some synthetic rated (TCW-3 on the container) 2-stroke oil in the gas at about 100:1 when you get it back together. It will barely smoke and the 2-stroke oil is designed to lubricate during combustion and works well at freeing stuck rings.

    Dave Neptune

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    • Marty_B
      Senior Member
      • Feb 2023
      • 32

      #3
      Great advice! Thank you very much!

      Comment

      • Marty_B
        Senior Member
        • Feb 2023
        • 32

        #4
        I should receive my valve spring compressor in the mail today and hope to remove the valves. The valves and seats look pretty bad. I have done a bit of research regarding having seats cut and will see how bad the valves are when I get them out. Where should I go to get the valve seats cut and also since the valves are stuck pretty tightly, should I replace the valve guides?

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        • Dave Neptune
          Afourian MVP, Professor Emeritus
          • Jan 2007
          • 5099

          #5
          Marty, almost any good automotive machine shop should be able to help you out. Cutting the seats is not a difficult task. There are some "auto shops' that rent tools like seat cutters if you wish to do it yourself. I had to replace a burnt exhaust valve when I bought my boat with the engine seized. I removed the valve and borrowed a seat cuter and did it in the boat, then replaced the valve. I must say I do and did have a lot of machining experience and consider the task an easy one.

          As far as guides they are not as important in a flathead as they are in an overhead due to gravity. Unless they are very worn I would not bother especially since the hi-nickel block of the A-4 is about the best material for guides and again a flathead is not fussy about guides.

          You may find the valves will be just fine once cleaned up and just regrinding them will work just fine. They may even be fine just by lapping them back in.

          If the seats are really bad they can be bored out and even harder ones can be easily installed. And if the guides are badly worn they to can be replaced. However this work should be done in an automotive machine shop.

          Dave Neptune

          Comment

          • Al Schober
            Afourian MVP
            • Jul 2009
            • 2031

            #6
            If you have an auto repair shop that you trust, ask them where they send cylinder heads for work. Then do talk to them and see if you will be comfortable working with them.
            Last engine I went through, I had the shop do the valve seats. Intakes cleaned up OK but the exhausts needed the installation of carbide seats. No extra charge. Once the valves are out and faced (shop work again) the guides can be evaluated. Rather than replacement, they may only need to be cleaned out with a reamer. This would also be a good time to have the shop drill and tap the side the reversing gear casing. Do a search on 'Kaminsky modification'.

            Comment

            • Marty_B
              Senior Member
              • Feb 2023
              • 32

              #7
              Thanks again Guys. This information is really helpful.

              Comment

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