Next piece of the puzzle

Racers Hangout

  1. dvw

    dvw Well-Known Member

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    My friend Paul comes through again. There was miscommunication when my pistons were ordered. They came with no gas ports. Paul built a fixture to hold tolerance and got it done, at home.
    Doug 19261.jpeg
     
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    • 69 Sleeper Bee

      69 Sleeper Bee Well-Known Member

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      Just saw this post and I am not a racer but what is the purpose of gas ports ?
      Looks cool though.
       
    • 493 Mike

      493 Mike FBBO Gold Member FBBO Gold Member

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      The combustion pressure is directed behind the ring which increases its radial pressure and reduces blow by, there by making more power.
      Mike
       
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      • LemonWedge

        LemonWedge Well-Known Member

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        Nice to see the puzzle is coming together, Doug!
         
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        • Budnicks

          Budnicks You Can Just Thank Me Later FBBO Gold Member

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          not to over simplificate it
          it helps gasses force the top rings out & seal better
          less blow-by
          it's an old SS or P/S trick
           
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          • 69 Sleeper Bee

            69 Sleeper Bee Well-Known Member

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            it took me a minute to wrap my brain around the concept but I think I get it.
            And it is just into the top groove’s compression ring, not both rings right.
            Damned ingenious actually.
             
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            • Hemirunner

              Hemirunner Well-Known Member

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              • vintage chromoly

                vintage chromoly Well-Known Member

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                • dvw

                  dvw Well-Known Member

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                  Made more progress. Measured coil bind of each spring. All exceed the Pac spec. Set all the installed heights +/- .005". Checked cc's on every chamber. All were within .5cc except 2 chambers which were 1cc small. Heads all assembled. The head is bolted to the bench with a piece of cardboard to protect the deck face. The in the car spring tool works well. My air powered compressor won't even touch these springs, 307/810 psi.
                  Doug 20220112_160826.jpg 20220112_160830.jpg 20220112_165350.jpg
                   
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                  • LemonWedge

                    LemonWedge Well-Known Member

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                    Hard to believe I’m not already aware, but what heads are in use here, Doug?
                    Wishing you the best with this updated bullet.
                     
                  • dvw

                    dvw Well-Known Member

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                    Heads are older pair of -1s hand ported by the late Jeff Koybitski at Modern cylinder head. They've been welded on a few times but make good power. Completed some more today. Cam bearings are in.. of course not w/o issue. I missed where the broken rod had nicked the front of the #3 cam bearing tunnel. Had to pull it back out and dress up the area. Fortunately a friend had a partial set of bearings. Got it all squared away.
                    Doug

                    20220113_153958.jpg 20220113_150415.jpg
                     
                    Last edited: Jan 16, 2022
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                    • dvw

                      dvw Well-Known Member

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                      Now time to check rod bolt stretch and rod bearing clearance. I had previously checked all the rod dimensions (Molnar 7.100"/ 2.200"/.990") and they were spot on. For those of you haven't checked rod bolt stretch. Each bolt length is measured for individual length and recorded. I fabricated a "standard" to zero the gauge. Then each bolt is compared to the standard. They all vary in length from .0001"-.0050" +/- . I used the torque angle method to tighten the bolts to 30lb/ft with an additional 60 degrees of rotation afterwards. Then using the gauge you measure the bolts in the rod while torqued. A few needed a slight bit more rotation to reach the desired. 0060"-. 0064" stretch spec. The crank (Molnar 4.500") was measured previously (all mains 2.7500", rods 2.1995") with .0000 out of round or taper. You set the mic to the journal diameter and zero the dial bore gauge in the mic. The bearings were all checked with the dial bore gauge. Clearances came in as expected. .0026+/- .0001". This is a time consuming process. You also need to have a clamp fixture to properly hold the rod while torqued. Also a way to grab the cap to remove the caps.
                      Doug
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                      Last edited: Jan 17, 2022
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                      • LemonWedge

                        LemonWedge Well-Known Member

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                        Class is in session! Thanks for sharing, Doug!
                         
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                        • Wookie316

                          Wookie316 Well-Known Member

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                          I always learn when I read your threads. Thanks for sharing. I appreciate your input to this forum.
                           
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                          • Gunner1

                            Gunner1 Well-Known Member

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                            You would be surprised at how many calls I fielded from people who didn't check individual bolt lengths before torquing for stretch. .001 is a substantial difference when your looking for precision finals. Your rod and main numbers are off the charts. .0000 is what we aimed our billet cranks to. I dont know who Molnar is sourcing their stuff from but I am hearing a lot of very good things about them.
                             
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                            • dvw

                              dvw Well-Known Member

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                              Well went back to the heads. Took the rotate scotch brite to the 2 small chambers. Now all are 57.5cc +/- .5cc. Dusted the valve pockets on all the pistons to remove the sharp edges. Then deburred all the gas port holes. Tight getting into the ring groove as its only .9mm (.0365) wide. Still have to check the actual deck height. But preliminary math shows 15.3-15.4 to 1 with a standard .051" Cometic gasket.
                              Doug
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                              20220116_165636.jpg
                               
                              Last edited: Jan 20, 2022
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                              • khryslerkid

                                khryslerkid FBBO Gold Member FBBO Gold Member

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                                :eek:
                                 
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                                • RemCharger

                                  RemCharger Well-Known Member

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                                  Very nice post. Thanks.
                                   
                                • Gunner1

                                  Gunner1 Well-Known Member

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                                  Is this motor corn fed or race gas?
                                   
                                • dvw

                                  dvw Well-Known Member

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                                  Renegade 114+ has been run in it for 9 years.
                                  Doug
                                   
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