How to free up stuck valves

Unknown
Unknown
edited November -1 in HUDSON
Anyone got any suggestions/experience on how to free up stuck valves on an engine that's been sitting over winter with out takeing it apart ? BUD

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  • PAULARGETYPE
    PAULARGETYPE Senior Contributor
    Well i would put kroil in the cyl,s and crank it a few times and let it sit a day or two spraying it down a few more times while cranking put your finger over the spark plug hole and see if you get some compression i have bent a screw driver and tapped the center of the valve to push it back down to get it freed up. Be careful not to bend the valve
  • SuperDave
    SuperDave Senior Contributor
    Yep, Kroil is the best, second choice would be Marvel Mystery oil. If you take your time and let the oil work, make sure the engine stops in a different position than normal. A six will usually stop one of three poitions, Access to the flywheel is handy to move the crank small amounts at a time and leave it overnight. Pulling the valve covers and working with the bottomof the valve and spring is also a way to do it. You will see the large gap and know which valve it is.. Then you ask the question.. why did it stick? leaky headgasket? Then you need to pull the head anyway..At least my luck runs that way..
  • Geoff
    Geoff Senior Contributor
    The usual cause of stuck valves after sitting, is rust around the stem, which is exacerbated by the practice of coming home, parking in the driveway, emptying the car out, giviing it a wipe over, etc. This allows the engine to cool down, and then you start it up, drive in into the garage, and turn off. This leaves a corrosive coating of acid moisture around the valve stems and guides. If you are putting the car away for an extended period the best thing to do is choke it off by pouring oil down the carby (Kroil or Marvel, or whatever) whislt racing the engine. This will create a lot of smoke, both when doing it, and when re-starting, but leaves a good coating around the valve stems, and it is better then freeing up stuck valves. It is best to remove the tappet covers and see how many are stuck. If only one, then use a pair of vice-grips on the stem and try twisting it. If it is only superficially stuck it will usually pop down, but if it is real tight then you may need to remove the head and operate. If the valve doesn't pop down easily then there is a danger of driving the guide down if you hammer too hard. Good luck!

    Geoff.
  • Uncle Josh
    Uncle Josh Senior Contributor
    If it's runnng, dribble some Marvel Mystery Oil down the carb. It'll usually free it up.
  • [Deleted User]
    [Deleted User]
    Usually it is an exhaust valve thats stuck. I think this is caused by the carbon build up in the recess at the top of the guide. By the way does anyone know what purpose the recess at the top of the exhaust guides serves? It is always full of rock hard carbon, so that defeats any purpose. Just wondering?
  • Clutchguy
    Clutchguy Senior Contributor
    cargray wrote:
    Usually it is an exhaust valve thats stuck. I think this is caused by the carbon build up in the recess at the top of the guide. By the way does anyone know what purpose the recess at the top of the exhaust guides serves? It is always full of rock hard carbon, so that defeats any purpose. Just wondering?



    I think for better cooling of the guide??,don't know doe sure
  • Richie
    Richie Senior Contributor
    cargray wrote:
    Usually it is an exhaust valve thats stuck. I think this is caused by the carbon build up in the recess at the top of the guide. By the way does anyone know what purpose the recess at the top of the exhaust guides serves? It is always full of rock hard carbon, so that defeats any purpose. Just wondering?



    When I built my Plymouth flathead and installed new guides I was told by a Plymouth guru to be sure I installed the exhaust valve guides with the counter bore upwards and the intake guides just the opposite. The reason was for better heat shielding. Richie.
  • Geoff
    Geoff Senior Contributor
    The recess is actuallly to stop the valve from sticking on carbon build-up. The inlet valves don't need it. The thinking iis that the carbon will only build up around the part of the valve stem that is actually in the gas flow, hence the recess, to allow the valve to go down cleanly into the guide without jamming. Nothing to do with cooling, in fact the stem will actually be slightly hotter, as heat is transferred away by the guide contact with the stem. If using a valve lubricant in the fuel, do so sparingly, as this builds up on the stem as well as on the face if too much is used.
  • tigermoth
    tigermoth Expert Adviser
    geoff's explanation makes the most sense to me. in regard to plymouth guru, this maybe one of those things where an experienced guy knows what he is supposed to do, but maybe a little fuzzy on the why. regards, tom
  • harry54
    harry54 Senior Contributor
    kroil is the way to go works great....
  • [Deleted User]
    [Deleted User]
    Kroil is wonderful stuff, but I havnt found anything that would desolve the carbon buildup in the ex valve guide recess [the manual calls it a counterbore] use a 13/32 drill bit on later splasher motors to drill the carbon out. and sometimes it is almost like drilling cement . Thanks for the info on reason for "recess"
  • bull_islander
    bull_islander Expert Adviser
    another vote for Kroil. If you can't find it locally, you can get it here: www.kanolabs.com
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