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Loosening stuck screws ,a common mistake

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  • Loosening stuck screws ,a common mistake

    I have been fixing old stuf for 68 years. When taking things apart that have multiple screws, I noticed that the last screws were allways the hardest . This is because all of the stress from warpage and gasket swelling and corrosion buildup is on the final screws.SOO,NOW when I loosen a screw ,I snug it up right away. After I have done this to all of the screws, it is safe to completly remove them one at a time.I see you tube videos of mechanics installing heads on engines,first tourqueing the bolts to 30 foot pounds then 50 then final,so that they get a nice even clamping and don't warp the heads.Yet these same guys will just remove the headbolts with a highspeed impact with no thought of the stress that they are imposing on the final screws. I hope this helps someone from screwing things up.Edwin Dirnbeck

  • #2
    If for example, all but one head bolt were removed...what kind of stress is on the final bolt?...what force is the head exerting on that specific spot?

    I don't think gasket swelling would play any part unless the gasket chose to swell greatly in that one spot as you neared completion of the bolt removal

    I don't doubt your new technique works, it just seems your reasoning might be off.

    John

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    • #3
      The reasoning may be off (or not) but I too use the method he described and have for years even to loosening head bolts in sequence, on the heads I break them individually then snug them back down until all have been broken loose then remove them. Maybe it don't help but for sure it's very good insurance and little extra trouble for a huge return if it does indeed prevent any warpage -even once!

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      • #4
        I don't do that routinely, but when the last one is stuck I will tighten the others to get it loose! 50 years of experience says it works, but doesn't say why.

        Mike

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        • #5
          Sometimes you never know which screws are going to give you a hard time.

          JL................

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          • #6
            Thank you Edwin. I think your reasoning is correct.

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            • #7
              On critical items such as cylinder heads or intake manifolds and pretty much anything with a gasket surface I like to back each bolt off about 1/4 turn in a sequence that more or less equalizes the pressure while loosening, i.e. loosen a bolt at one end then the other, maybe a side then and opposite side and so on 1/4 turn at a time until all are loose, then run them out with a power tool.

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              • #8
                Originally posted by firbikrhd1 View Post
                On critical items such as cylinder heads or intake manifolds and pretty much anything with a gasket surface I like to back each bolt off about 1/4 turn in a sequence that more or less equalizes the pressure while loosening, i.e. loosen a bolt at one end then the other, maybe a side then and opposite side and so on 1/4 turn at a time until all are loose, then run them out with a power tool.
                I have for years felt it was very important to do this with cylinder heads, especially Aluminum heads. Maybe it's not necessary but I personally think the OP is spot on and his reasoning of the situation is sound.

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                • #9
                  The technique may work, but following a removal pattern to prevent head warpage is unnecessary. There's no way the head will twist to it's elastic limit by removing bolts in any sequence. Torque patterns aren't used to prevent head warpage. They're to achieve even clamping pressure.

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                  • #10
                    I usually follow this advice as well. If you loosen all the bolts except one on the end of a cylinder head, any swelling of the gasket or other force along its length to the other end provides a huge mechanical advantage so that the head acts as a lever on the last bolt. It may also be worthwhile to use a torque wrench for loosening the bolts to see if they were properly torqued at assembly. Of course, corrosion could make them need more torque to remove.
                    http://pauleschoen.com/pix/PM08_P76_P54.png

                    Paul: www.peschoen.com
                    P S Technology, Inc. www.pstech-inc.com
                    and Muttley www.muttleydog.com

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                    • #11
                      I always slacken off screws in order, a bit at a time. Except one time I was taking off an aluminium head, it wouldn't come off, even with levers until I noticed one bolt in the middle hiding behind something, oh dear, not good. I took the head into work and checked it on a surface table, it hadn't warped at all, what luck!

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                      • #12
                        "Torque patterns aren't used to prevent head warpage. They're to achieve even clamping pressure. "

                        Because without even clamping pressure.................the head will warp!

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                        • #13
                          Most head bolts these days are "one time use" bolts so they don't worry about hurting them on the way out.

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                          • #14
                            Originally posted by mikegt4 View Post
                            Most head bolts these days are "one time use" bolts....
                            Heck you can kinda say that about the whole engine these days. There are a few exceptions, but in my opinion newer engines are so hard to get to I don't even want to try. They make it extremely difficult just to change the spark plugs for dog's sake.

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                            • #15
                              I've always used the OP's technique on cars and firearms, been working on both for well over 50 years, and so far, I've yet to have a problem with a cylinder head, a side plate, receiver, etc. but I have had lots of the latter brought into the gunshop that were stuck, because the owner didn't use this technique.
                              Side plates, receivers halves, etc. don't have gaskets, so who knows what the real cause of the bind up is.
                              Steve
                              NRA Life Member

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