Announcement

Collapse
No announcement yet.

What Happened To These?

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

  • What Happened To These?

    Here is a picture of 4 of my 16 valve shims (well technically I have 8 shims and 8 guides, lol). These were the only ones that were worn down. Here's the kicker... the motor has 122 miles on it! Everything else looks bitchin and compression is perfect. Nothing else is bad in the motor. Any ideas on how this happened and how I can stay away from it happening again? Thinking of sending my cams out for WPC as well.

    General Motor Specs that directly interface with shims:
    S13 SR20DET
    Tomei Solid Lifters
    Tomei 260 Cams
    WPC Treated Rocker Arms
    Tomei/Nissan shims & Guides
    Supertech Ti Spring Retainers
    Supertech Dual Valve Springs

    Complete motor specs can be found on 2_Liter_Turbo if you really want to know the rest.

    www.2LiterTurbo.com (Personal Site)
    96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

  • #2
    Are they all from the same area? Randomly spread around the head?

    Could be a hardness issue?

    Comment


    • #3
      randomly around the head. only 4 were bad out of 16. All shims, no guides.

      My thinking of possibilities:
      - These missed heat treat
      - Valve train settled too much during the 122 miles to cause too much gap (these were gapped within spec in the beginning).
      - 275 lb supertech valve springs are just too damn stiff?
      - possibility of keepers giving out, but didn't notice anything out of the ordinary. I'll have to check when I get a spring compressor.

      www.2LiterTurbo.com (Personal Site)
      96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

      Comment


      • #4
        BTW, the pads on the rocker arms look fine.

        www.2LiterTurbo.com (Personal Site)
        96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

        Comment


        • #5
          Did you measure the lash before you removed them by chance? But if nothing else is worn/out of place, that strongly points to a defective part.

          Comment


          • #6
            I measured the lash afterwards yes. The cupped ones were way loose at that point, lol. They were all within spec or slightly tight before the engine was ever started though.

            www.2LiterTurbo.com (Personal Site)
            96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

            Comment


            • #7
              How do the threads on the adjusters look like? I suppose they could have been undertorqued and loosened causing the damage.

              Sorry for all the questions, my current job is failure analysis on CAT engines so this is interesting to apply a bit of it to SR20s!

              Comment


              • #8
                The adjusters are solid. The adjustment is in the shims themselves (varying thickness).

                www.2LiterTurbo.com (Personal Site)
                96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

                Comment


                • #9
                  Wow, major dumb moment right there. Basically narrows it to your thought that they missed heat treat would be correct, though perhaps wait till some of the others chime in to be sure you haven't missed something.

                  I don't think its the springs, otherwise it would show up on more of them. And I assume when they were initially set, they had a flat, smooth upper surface?

                  Comment


                  • #10
                    Yeah, lol. they were perfectly flat and smooth. A friend of mine who also has supertech springs rounded his cams after 1000 miles. I personally think the springs are too stiff for the SR. I'm seriously thinking about swapping them out for the Tomei Type-B setup. It'll cost me about $400 after selling the supertechs. Sucks... lol. Trying to get some input in that regard though.

                    www.2LiterTurbo.com (Personal Site)
                    96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

                    Comment


                    • #11
                      Are the rest of them perfectly flat and smooth still?

                      Comment


                      • #12
                        Yes sir. But if these had jsut a slight increase in gap, could the higher spring rate have caused too much of an impact against these oem shims to cause them to dish out as they did.

                        www.2LiterTurbo.com (Personal Site)
                        96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

                        Comment


                        • #13
                          were these dlc coated? if so you could have had just enough oil starvation to scratch them. 1 time would be enough to star the destruction process..

                          Comment


                          • #14
                            The shims were not coated in any way.

                            www.2LiterTurbo.com (Personal Site)
                            96 240SX SE: Track Car | 90 Skyline GTR: Bucket List Car | 07 Legacy Spec B: The DD

                            Comment


                            • #15
                              But if the gap was set, there shouldn't be any way for the gap to increase, other than material being removed, or the spring sagging/being too short/out of spec. I don't think the spring would be the problem (with regards to allowing a small gap due to settling/being out of spec).

                              Although its possible a keeper/retainer was not full seated or there was a burr on something so that when you set lash it was within spec, then once the engine ran the burr was compressed/removed and everything seat and then a larger gap.

                              Comment

                              Working...
                              X