Welcome Guest - Sign Up today
Welcome Guest - Sign Up today

Announcement

Collapse
No announcement yet.

adjusting valves?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • adjusting valves?

    When you adjust your valves will the valve springs compress slightly or should they not compress at all until the valve starts to open? My manual says to go one full turn once the pushrod play is gone. When I do this and adjust one full turn the spring compresses a little? Is this normal or wrong? My worry is the valve is opening as the spring compresses, or is there play in the spring until the valve opens? Any yes, I am doing this in the right order and how it is suppose to be done, both valves are closed at tdc. Any help would be appreciated.

  • #2
    Re: adjusting valves?

    What are you adjusting the valves on?

    They are hydraulic lifters, the springs will compress a little when you go one turn down, but should open back up fairly quickly and allow the valve to close. If the spring stays compressed, then the lifter is sticking.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

    Comment


    • #3
      Re: adjusting valves?

      It is a 120 2.5L (1978). So after they compress once I turn them down a turn they should come back up?

      Comment


      • #4
        Re: adjusting valves?

        Thanks Don S

        Comment


        • #5
          Re: adjusting valves?

          Originally posted by Don
          the springs will compress a little when you go one turn down, but should open back up fairly quickly and allow the valve to close.
          Don S.


          Please, no PM's (Private Messages) regarding boat/engine problems.
          That is what the forums are for.
          Only forum/moderator issues will be answered in PM's.

          Comment


          • #6
            Re: adjusting valves?

            That one turn down amounts to a pre-load on the hydraulic valve lifter. Valve spring pressure will cause the inner part of the lifter to settle into the outer part of the lifter. I hope you have the engine rotated so the lifter you are adjusting is on the flat of the cam and not up on a lobe.

            Comment


            • #7
              Re: adjusting valves?

              Yeah, it was rotated right.

              Comment


              • #8
                Re: adjusting valves?

                You have got good advice here so far. Make sure before you adjust the engine is warmed up to normal tenperature.

                Understand what you are doing. Hydraulic lifters should be adjusted to the center of travel so you go to zero clearence plus one turn down on most engines. If you turn it down slowly then the valve spring should not compress. Instead the spring in the lifter is compressed to the center of it travel and some oil is forced out. This works very good if all the lifter are good and not sticking. However if you has a sticking lifter then you can end up with a valve open. You should hear the low speed miss. To be sure do a compresson check when done.

                If you do not adjust to the center of travel then tappets can be noisy and the engine will be down on power because the valves do not open enough to get gas and air in and exhaust out.

                When I adjust I do it a different way but it is messy and you can not do it without engine running. If all the lifter are good will end up at the same point. What I do is with the engine warm pull the valve cover and adjust each cylinder while on its conpression Stroke near TDC for that cylinder. Then I start engine and go down very slowly until the engine start to miss. You must go slow to allow the oil to work it way out of the lifter. Then I come back up until run without a miss then up one turn. Do that for each valve. Just to be sure I still do a compression check when done.

                If all the lifter are good will end up adjusted the same. But if You have a lifter without full travel or sticking then instead of the valve being held open it will be a little loose. I should say also this is much eaiser on a 4 cylinder than on a 8 cylinder because the miss is much mor noticeable on a 4 than an 8.

                Anyway you do it I suggest a compression check when done.
                Have some fun and enjoy the Great Outdoors.
                Love to fish out of Bodega Bay, California.

                Comment


                • #9
                  Re: adjusting valves?

                  While you may disagree Boatist, that is not a good way to adjust hydraulic lifters on a GM engine. Adjusting a lifter downward to create a miss means you have a valve too far open risking contact with a piston. You adjust them on a running engine by "loosening" the ball nut until the lifter clatters, "tighten" until the clatter just quits (zero lash), then go 3/4 to 1 turn down. If you do this on a regular basis, cut the center section out of a rocker cover so you can access the ball nuts. The rocker cover at least cuts down some of the oil flying around if you place a rag over the area where you are not working. If you want to get even fancier, use a Greenlee punch to make a socket access hole over each nut. Put a rubber plug in the holes you are not adjusting. This is simply an adjustment aid and obviously not left on the engine permanently.

                  Comment


                  • #10
                    Re: adjusting valves?

                    If you go down slow until it just starts to miss you will not come closes to tagging a Valve.

                    I just seen several friends who had a bad manifold and got water in the back cylinder. They took the head in and had a valve job done. Slapped the head back on installed a new manifold. Adjusted the valves per the book and went out for a day on the water. Boat ran fine but coming back to the dock noticed it was missing again. Investagation showed a burnt valve because his 25 year old lifter were stuck and the little spring did not push the lifter back up. So when he adjusted down one turn with the lifter stuck down left the valve open.

                    Now you can install all new lifters or check each lifter. I personally clean and check them one at a time then install back in the same location before going to the next.

                    I also have a valve cover with the top cut out and at idle will get only a drop or two of oil out of the engine.

                    Most important thing is to do a compression check when done.

                    Sure it take 15 minutes. Also listen to your engine and carry some tools just in case.
                    Have some fun and enjoy the Great Outdoors.
                    Love to fish out of Bodega Bay, California.

                    Comment


                    • #11
                      Re: adjusting valves?

                      So let me get this straight -- one turn down from zero lash in a stuck lifter plunger caused a burned valve. But using your procedure you actually create a miss because the lifter plunger is forced well past the center of travel but that won't cause a burned valve. That little spring under both conditions will cause the same failure (assuming of course the lifter was not checked as it wasn't in your example). And whether you go slow or not on the way toward the miss means the valve is being held open -- or it woudn't miss. Either way, it wasn't the factory procedure that caused the problem, it was a stuck lifter and that's also why there is very detailed lifter leakdown test procedure in the manuals. My whole point with this is that one turn down from zero lash leaves nothing to guess work. In fact since you bothered to create zero lash as the first part of the procedure, you could slimply do the one turn down and be done. One turn is a mechanical measurement based on the stud thread pitch. Your process has you going down until a miss occurs (your ears are a poor ruler). Back until the miss goes away, then one turn up. In my view that proves nothing -- you have no idea where that lifter plunger actually is. I'll stick with the process that has served Chevrolet engines with hydraulic lifters since 1950.

                      Comment


                      • #12
                        Re: adjusting valves?

                        Thanks for all the help. I do have a small miss when it is idling below about 800rpms, would that be valve adjusted wrong? Also, since I adjusted them it seems to start harder, especially after I shut it off and let is set for 5-10 minutes. Would the valve cause the hard starting or probably just carb float adjusted wrong? It seems to run fine above 800-900 rpms though??? Timing is correct also. If compressions checks out ok then should I be checking the carb? Last I checked compression was between 120 and 125 on all four cyclinders.

                        Comment


                        • #13
                          Re: adjusting valves?

                          Since you noticed the difference after valve adjustment that's probably part of the problem. Did it miss before you adjusted the valves? Idle mixture screws may be misadjusted as well. I doubt float level would cause the problem unless it is way too high which would cause an overly rich mixture. Was compression checked before or after you adjusted the valves. If before, then you might want to check it again. If you have a lifter adjusted too tight you'll have a miss as the valve will be held partially open and compression will be low. Static valve adjustment must be done according to the service manual. If each lifter is not on the flat (low spot on the cam (valve fully closed), adjustment will not be correct. To locate the miss, use an insulated pliers and one at a time pull a plug wire. Each time you pull a wire the engine should drop off and run rougher. When you hit the cylinder(s) that have misadjusted valves, there should be little or no change since its already running bad. Even though you think you had the engine turned so the lifters you were adjusting were on the low spot on the cam, you can tell by looking at the valve ends of the rocker arms whether or not both valves are closed. If both are not in exactly the same position, those valves are not closed. Intake and exhaust valves will never both be fully open at the same time. Start with the basics. Tune up, dwell (if points system), timing, idle mixture, choke setting (if applicable), good wires, good plugs, good compression, and good valve adjustment.

                          Comment


                          • #14
                            Re: adjusting valves?

                            Thanks for help, gotta check it out once I get some time:%

                            Comment


                            • #15
                              Sign up today
                              Re: adjusting valves?

                              Make sure and do a second compress test with the engine warm.
                              Actually if I had the head off for any reason after the first good heat cycle or on the water test I usually retorque the head and do another compression test. Most head gaskets today do not need retorqued but I still do it at least once. If for some reason bolts move more than just tiny then good idea to recheck the vlaves.

                              A leaking or burnt valve will show up as a low speed miss and sound normal at higher RPMS. That is why when adjusting valves I do it at below normal RPMS (Around 500).

                              Have some fun and enjoy the Great Outdoors.
                              Love to fish out of Bodega Bay, California.

                              Comment

                              Working...
                              X