Announcement

Collapse

Get more Tips, Specs and Technical Data!

Did you know... this Forum is a service of the Studebaker Drivers Club? For more technical tips, specifications, history and tech data, visit the Tech Tips page at the SDC Homepage: www.studebakerdriversclub.com/tips.asp
See more
See less

Valves slapped pistons.

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

  • Valves slapped pistons.

    Pulled the heads off my 289.
    Every piston had marks from the valves hitting them.
    Most were almost unoticable but a couple pistons were noticablly marked.
    Any input on reusung the pistons or why the valves were slapping?
    Doing a complete rebuild and want to solve the issue.
    Heard some thought that it might have been wrongly adjusted vales.

  • #2
    Possibly a previous rebuild with the deck shaved and they did not check the clearances of the valves to the pistons ?

    Comment


    • #3
      I have thought about that.
      It seems unlikely since the engine hasn't been ran since 1968.
      Your saying someone might have shaved the block or heads?
      How can i check?

      Comment


      • #4
        Intake or exhaust valves hit? Are the valves stock diameter?

        I would Degrease the tops of a few of the most dented pistons, on one bank, then Lay strips of modeling clay ~ 1/8 inch thick across the dents. Spray the valve heads with a little WD40 or something to keep the clay from sticking. Then I'd Put the head back on with an old gasket and torque the head bolts and install the pushrods rockers etc and adjust the valves. Then I would wind the crank through a few revolutions. Finally, take the head off and check the clay for dents. Use a razor blade to slice through dented clay to allow removing half to judge thickness of the clay in dent, which is an indicator of valve to piston clearance. I'd expect stock parts to have way more than 0.100 inch, which is about the minimum I'd want.

        If there is sufficient clearance now, I'd suspect the cam was installed badly timed in the past, or maybe a timing gear failed.

        If the clearance is insufficient I'd check cam timing. Or, Maybe there's a serious hot rod cam in there.

        Comment


        • #5
          Betcha a donut everything is fine...
          Probably over revved the snot out of it and floated the valves, knocking the crud off the pistons.
          Jeff
          HTIH (Hope The Info Helps)

          Jeff


          Get your facts first, and then you can distort them as much as you please. Mark Twain



          Note: SDC# 070190 (and earlier...)

          Comment


          • #6
            I would bet that the engine has been over revved in the past as that is usually what causes the valves to hit the pistons. The stock Studebaker valve springs aren't very high tension springs and will allow the valves to float at a relatively low rpm. This is much easier to do if the engine is equipped with a 4 barrel carburetor and a standard transmission. I would recommend reboring to the next oversize and installing new pistons as there is a good chance that the cylinder bores are tapered and out of round anyway. I haven't done a Studebaker engine rebuild in the past 30 years without a doing a rebore and installing new pistons as the engine will run better and last a bunch longer. I know the cost of the job will be substantially higher, but in my opinion, the added expense is money well spent. Bud

            Comment


            • #7
              It is a 2bbl 4 speed.Knowing the history of the car i am sure it was ran extremely hard.
              From what i recall the former owner is still in prison......
              The block is going to be bored 30 over.We have new pistons.
              If it is valve float are there springs that can cure that?

              Comment


              • #8
                Timing gear looks brand new,In fact the engine looks like it was ran yesterday inside.
                If it didn't have 2 stuck (gummed up)pistions i am sure it would have ran.
                I'll keep your suggestion in mind when we put it back together.

                Comment


                • #9
                  Originally posted by DEEPNHOCK View Post
                  Betcha a donut everything is fine...
                  Probably over revved the snot out of it and floated the valves, knocking the crud off the pistons.
                  Jeff
                  That's what i am hoping.Just want to make sure.

                  Comment


                  • #10
                    Really, really rare for Stude V8 valves to hit the pistons. In fact, I can't ever remember seeing marks on one I've torn down. With the low valve angle head design and low-lift camshaft, Stude V8 valves and pistons just don't get very close together.

                    If the marks are as light as you indicate, the pistons should be fine to reuse. I'd spin the valves in a lathe with a dial indicator to check runout. There is a lot of leverage on the edge of a valve and a solid hit can bend one.

                    Just for shirts and gargles, check the timing marks on the crank and cam. Wouldn't be the first time someone put them together a tooth off.

                    thnx, jack vines
                    PackardV8

                    Comment


                    • #11
                      You can install valve springs for an R series engine as they are a higher pressure spring meant for the higher revving Avanti engines. You would need to install an aluminum timing gear on the cam as I don't believe that the fiber gear will survive with the heavy duty springs. If you are rebuilding a stock engine, the stock springs should be fine. I would recommend replacing all of the valve springs as I don't trust valve springs that are close to 50 years old. They will lose their tension over time or they can break and that will cause you big problems. Bud

                      Comment


                      • #12
                        I have run 289s up to valve float many times. I have never had a valve to piston problem. Maybe I was just lucky. I didn't think that they were that close to start with. My first thought was the heads and/or block were cut too much. Also, the timing may have gone away. I would at least check the straightness of all of the valves if not replace them and use new valve springs, either stock or heavy.
                        Gary L.
                        Wappinger, NY

                        SDC member since 1968
                        Studebaker enthusiast much longer

                        Comment

                        Working...
                        X