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  • GM flat plane crank

    Pretty cool - more then 2 hp per cubic inch.....
    With Chevrolet's new Z06 reveal, comes new details on the all new 5.5L twin-cam LT6 engine that will spin to the moon.
    Doing it all wrong since 1966

  • #2
    It would be useful to have a pic of a flat plane and conventional crank side by side. I'll go look.......

    Dan

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    • #3
      Originally posted by SuperBuickGuy View Post
      Pretty cool - more then 2 hp per cubic inch.
      Thanks, that's exactly what I wanted.

      Click image for larger version

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      • #4
        Originally posted by DanStokes View Post
        It would be useful to have a pic of a flat plane and conventional crank side by side. I'll go look.......

        Dan
        Monster for the win...
        Doing it all wrong since 1966

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        • #5
          Originally posted by Monster View Post

          Thanks, that's exactly what I wanted.

          Click image for larger version  Name:	gm-announces-5-5l-lt6-670hp-four-cams-and-a-flat-plane-crank-2021-10-26_12-31-32_984028-1440x960.jpg Views:	25 Size:	147.3 KB ID:	1308446
          Pdub - notice that as you look down the crank the first crankpin closest to the viewer is at about the 2:00 position and the next crankpin is at about the 8:00 position, 180 degrees apart. In a conventional engine these would be 90 degrees apart. As you go rearward on the crank you'll notice that the center sets of crankpins are offset the same way and the front and rear sets match. Therefore the firing order is very different and, as a side effect, the engine sound is very different. Maybe someone (Dave G, Squirrel, John C maybe?) can tells us why they started building them with the 90 degree separation. I don't know what the advantage would be to the 90 degree configuration.

          Dan
          Last edited by DanStokes; October 28, 2021, 01:20 PM.

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          • #6
            Anyone remember when Warren Johnson ran a flat plane crank in his blue and white Olds Cutlass Pro Stocker? At the tree, the thing sounded like a cross between a chain saw and 2 stroke diesel motor.
            Last edited by studemax; October 28, 2021, 02:22 PM.
            Act your age, not your shoe size. - Prince

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            • #7
              Originally posted by DanStokes View Post

              Pdub - notice that as you look down the crank...

              Dan
              I HATE getting called on in class - I'm never ready. But now that you've pointed it out and described it, that's cool stuff!
              Charter member of the Turd Nuggets

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              • #8
                Originally posted by DanStokes View Post

                I don't know what the advantage would be to the 90 degree configuration.

                Dan
                The 90 degree V8 is better balanced, so runs more smoothly than a flat plane crank:



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                • #9
                  Originally posted by Red_Kitty View Post

                  The 90 degree V8 is better balanced, so runs more smoothly than a flat plane crank:


                  Yes flat crank v8s tend to shake like mad. The old timers that ran flat cranks in flatheads had to safety wire everything. Probably the most famous v8 with a flat crank was the NOVI first raced just before ww2, and raced into 1965. It never won, but it was awesome to hear running.

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                  • #10
                    A video may help, Youtube to the rescue!



                    Last edited by 65RHDEER; October 28, 2021, 09:23 PM.
                    Tim
                    Melbourne Australia

                    65 Hardtop Impala, 70 GTS Monaro, 93 "80" Landcruiser

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                    • #11
                      When I read the opening header,
                      I thought right away of a "Boxer Engine" !!
                      Corvette is going to build a Pancake Engine? A water cooled Corvair with two more cylinders?
                      Then I looked at the pix,....And same thoughts, in a V form, Shakes more than a Ugly Stripper !!!

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                      • #12
                        Originally posted by dave.g.in.gansevoort View Post

                        Yes flat crank v8s tend to shake like mad. The old timers that ran flat cranks in flatheads had to safety wire everything. Probably the most famous v8 with a flat crank was the NOVI first raced just before ww2, and raced into 1965. It never won, but it was awesome to hear running.
                        I'll be fine if I ever were to buy one, I had and rode a CR500 .... if you didn't wear gloves, your hands would fall asleep.
                        Doing it all wrong since 1966

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                        • #13
                          Originally posted by SuperBuickGuy View Post
                          I had and rode a CR500 .... if you didn't wear gloves, your hands would fall asleep.
                          I had one of those beasts ... loved the decompression lever !

                          Click image for larger version

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                          • #14
                            Originally posted by Monster View Post

                            I had one of those beasts ... loved the decompression lever !

                            Click image for larger version

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                            they were also excellent at not being stolen... you could kick for days and never get them started without knowing the trick.
                            Doing it all wrong since 1966

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                            • #15
                              Monster: SBG was talking abut the CR500, which is a TWO STROKE, the bike in your pic is an XR500, four stroke, apples vs pomegranates !


                              Originally posted by Monster View Post

                              I had one of those beasts ... loved the decompression lever !

                              Click image for larger version

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