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what are these for?

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  • what are these for?

    performance? durability? anyone?

    http://cgi.ebay.co.uk/Vauxhall-Monar...item4ceb9a0672

  • #2
    Increased capacity (swept volume), so will increase torque and power. The problem is that it will also increase piston speed, so you really need to lower the redline of your engine or longevity will suffer.

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    • #3
      piffle. take a hike over to hardcorels1.com and read the threads in the shortblock section around piston speed.

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      • #4

        It doesn't take much......

        Okay, I'll agree that anything can be built, and if you match components to that crank then you will not have a problem. Okay?

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        • #5
          Does that mean there is scope to increase the redline safely on a standard LS3 block then Rich ???

          And just because i'm blonde.......regardless of the crank, the pistons moving up and down are relative, 6500rpm redline with or without that crank equals the same doesn't it ??? or not ?? honestly asking this btw

          (Excuse me for not nerding up on your link a little)
          2009 Red Hot VXR8 LS3 Manual.......very "Smitten"

          sigpic

          "Power is nothing without control"

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          • #6
            I wonder what the Iron Nitrated bit is...

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            • #7
              i dont like the part that says "no heavy metal" i would have no music to listen too.


              araf is right about piston speed,

              the f20c engine for the s2000 was "stroked" from 2ltr to 2.2 ltr for the usa market because they cant drive properly.

              this resulted on the redline shifting from 9000 rpm to 8000 rpm because the piston speed would have been to high.

              the speed of the piston of the f20c is 25m/s @ 9000 rpm.so to keep the piston speed at that,due to the longer stroke of the 2.2 the lazy yanks lost the 9000rpm bit.

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              • #8
                Originally posted by Phantom Mark View Post
                And just because i'm blonde.......regardless of the crank, the pistons moving up and down are relative, 6500rpm redline with or without that crank equals the same doesn't it ??? or not ?? honestly asking this btw
                No - and this is where I probably screw up the maths.

                If we take an engine speed of 6500 rpm, then that's 108.33 revs per second - or .009 seconds per rev. Assuming (incorrectly) that changing direction is instantaneous then 50% is going up the bore, and 50% is coming down so the stroke of 3.625" (92mm) has to be doubled to give the total distance travelled in a cycle. This gives an average piston speed of 19.93 metres per second.

                If you have the longer stroke of 4.25" (107.95mm) the piston speed at 6500 revs increases to 23.38 m/s as the piston has to move further between top dead centre and BDC.

                Speed on it's own isn't a problem. The trouble is more to do with the strain put on the conrod and bearings by stopping the mass (piston) at top dead centre and then overcoming the inertia when you accelerate it the opposite way. The easiest way of preventing failure is to use a lighter piston (which then presents it's own problems) and strengthened con-rod.
                Last edited by ARAF; 13 November 2009, 11:53 AM.

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                • #9
                  Originally posted by ARAF View Post
                  complicated stuff





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                  • #10
                    Gotcha thanks Araf, I spent some time thinking about what I typed and how things must work and kinda reached a similar conclusion after I smashed my hands into my face for forgetting that RPM is measured at the crank and not at the piston /stroke lol.......duhuh Told ya I was being blonde
                    2009 Red Hot VXR8 LS3 Manual.......very "Smitten"

                    sigpic

                    "Power is nothing without control"

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                    • #11
                      Weak link stock is rod bolts for rpm. Otherwise plenty of blokes wind them out to over 7000rpm stock. Mine has been over 7000 a few times with a 4.1" stroke. But has the supporting parts to minimise risk.
                      On a stock engine you probably have room to move it a little, but you should do ARP rod bolts first then 7000 should be fine. Read up on ls1tech.com etc.
                      However there isnt much point winding them out that far unless you have the airflow and cam/intake to let you keep gaining power otherwise you are better off shifting up a gear to keep the engine in its power band.

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                      • #12
                        Rod bolts is major surgury and probably best saved for an engine being rebuilt to bigger specs then I guess, still nice to know, thanks
                        2009 Red Hot VXR8 LS3 Manual.......very "Smitten"

                        sigpic

                        "Power is nothing without control"

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                        • #13
                          Major?

                          If you call taking the sump off major then yeah. I know people have done it with the engine still in the car!

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                          • #14
                            Doh of course.........
                            2009 Red Hot VXR8 LS3 Manual.......very "Smitten"

                            sigpic

                            "Power is nothing without control"

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