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Valve Setting Question on SIX CYLINDER OHV 170

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  • Engine: Valve Setting Question on SIX CYLINDER OHV 170

    I know what the manual states about a 12vt light, setting the first cylinder on the 1-6 marking then use the light and rotate clockwise, etc till the next firing cylinder (5) and when the light gets lit, set the valves etc. BUT here is my question: since the manual tells me that both Exhaust and Intake are set the same, in this case between .25 and .27 with the feeler guage, why can I do this:

    First move the number 1 cylinder to its designated location on the timing wheel (1-6) and adjust both valves at .26. Then instead of using the light bulb method just rotate till the number 5 cylinder (which is next in line) piston comes up to its highest point in its travel within the cylinder wall and then adjust both exhaust and intake? and continue on. I guess what I am asking you is since both valves are adjusted to the same tolerance, why should I care which one is in the correct position as long as I know the correct piston is at its highest position?

    This question shows you how possibly stupid I am when it comes to engines but that's why I'm on this forum.

    Thanks for your time, sorry if this is a stupid question but please educate me .

    Thanks again.

  • #2
    Not stupid at all. I had to do it that way on my OHV six as I had an electronic ignition and no points. This meant I had to have the plugs out and gauge the height of the piston with something in the plug hole and move the crank until the relevant piston was at it's highest position, just like you supposed.

    After you run the engine and check the valve adjustment job with a vacuum gauge you will know if you did an accurate job or not. If you do it either way you are best checking the results with a vacuum gauge. Len.


    • #3
      Because there is something called valve overlap, where both the exhaust and intake valve are open at the same time to facilitate better cylinder filling. On the top of the compression stroke, the lifters are totally on the base circle of the cam.
      Remember the cam rotates 1/2 crank speed and the valves aren't totally closed until every other top dead center event. It HAS to be on the COMPRESSION cycle. It will not work just because the piston is at the top of the bore.
      Last edited by bezhawk; 12-28-2013, 07:10 PM.
      Bez Auto Alchemy

      "Don't believe every internet quote" Abe Lincoln


      • #4
        i did mine the same way skybolt. I had the head off at the time so it was easy to see when the pistons were at the top. then gapped both at the same time.


        • #5
          Originally posted by c locke View Post
          i did mine the same way skybolt. I had the head off at the time so it was easy to see when the pistons were at the top. then gapped both at the same time.
          That works with the Flathead but not the OHV six.


          • #6
            .... one reason to perform this adjustment hot and running......(most of our driveways or garage floors at this time have years of Stude oil leaks.....:-) )


            • #7
              I don't have a six any more to look at but from memory I would not like to do that job hot and running because of the exhaust manifold being in the way.


              • #8
                Not sure this is the right thread for this but first of all, THANKS for all your inputs, I appreciate them. Now to the next situation. I pulled the head off and since I don't have the right equipment to do a vacuum test or pull down test, etc, I filled the valve chambers with Brake Cleaner and after they were covered I watched the valves. Now this is under no pressure at all other than the springs are still holding the valves in their closed position and ALL the EXHAUST valves leaked. Brake fluid cleaner came running out immediately. I assume this is the time to take it to a machine shop for a valve job?


                • #9
                  I decided to take it to a machine shop for a "valve job". They have not torn it down yet to take a look but I should know something next week.