Damn, Preload makes a difference!

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  • Jon89LE
    • Dec 2003
    • 116

    #1

    Damn, Preload makes a difference!

    Well i just took my car to the track and by going from the 1/4turn of preload to 3/4turn i went from a 17.1 to a 16.5 with a 60ft of 2.21. Anyone ever figure out how much each turn on the iron head studs equates to on preload?
  • Wolf
    • Oct 2003
    • 181

    #2
    I think a motor gaining power with more preload means it would make more power with a bigger cam
    1995 camaro 3.4 5-speed

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    • geoffinbc
      Iron Head Enthusiast
      • Oct 2003
      • 5831

      #3
      What is the thread pitch? I calculated it before and 1.5 turns (factory spec) was .060 I believe. Cant remember for sure
      1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
      1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
      Because... I am, CANADIAN

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      • Jon89LE
        • Dec 2003
        • 116

        #4
        Oh Damn. Yea, you calculated it before but never got back to me on it! lol. If thats right then i should still tighten mine a bit more.

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        • geoffinbc
          Iron Head Enthusiast
          • Oct 2003
          • 5831

          #5
          I will go and get on of my old studs an throw a thread guage on it one day. Dont rush me :P . I will do it some day.
          1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
          1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
          Because... I am, CANADIAN

          Comment

          • Jon89LE
            • Dec 2003
            • 116

            #6
            Haha, it cool dude. I never knew preload could make such a big difference like that. Once break starts i may go ahead and tighten them a bit more depending on your PENDING information . If i can get my 60fts to around 2.1x that will be good for a few tenths off my quarter.

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            • geoffinbc
              Iron Head Enthusiast
              • Oct 2003
              • 5831

              #7
              Ok got it. The thread pitch is 1 thread per MM
              So 1 mm advancer per turn. Stock instructions say to advance it 1.5 turns. So that is 1.5MM of preload which is 0.0590551" close enough to .060" I think hey?

              Now crane suggests to adjust between .020 and .060. So adjusting to stock is right at the high side. But acounting for wear over time it is probabally optimal.
              1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
              1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
              Because... I am, CANADIAN

              Comment

              • RacerX11
                • Oct 2003
                • 1060

                #8
                You are forgetting to take into account the rocker ratio. By tightening the rocker adjusting nut 1.5 turns, you are moving the rocker pivot ball down by 1.5 mm. The valve end of the rocker stays put, so with a 1.5:1 rocker, the pushrod end of the rocker would move down by only 1mm (1.5mm / 1.5 rocker ratio), or 0.040", right in the middle of Crane's spec.

                Marty
                '99 Z-28 - Weekend Driver
                '98 Dodge Neon - Winter Beater
                '84 X-11 - Time and Money Pit
                '88 Fiero Formula - Bone stock for now

                Quote of the week:
                Originally posted by Aaron
                This is why I don't build crappy headers. I'm not sure, I don't know too much about welding.

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                • geoffinbc
                  Iron Head Enthusiast
                  • Oct 2003
                  • 5831

                  #9
                  Right. Forgot that part.
                  1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
                  1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
                  Because... I am, CANADIAN

                  Comment

                  • Jon89LE
                    • Dec 2003
                    • 116

                    #10
                    With what you said about the rocker ratios, im not sure if i have it right so let me know. Say you have a 1.5 vs a 1.6 rocker, would a 1.5 turn on each result in more preload on the 1.5?

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