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Engine balancing and the flywheel/pressure plate assembly

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  • Engine balancing and the flywheel/pressure plate assembly

    As you may or may not know, VG's are fairly well balanced from the factory by design. This is part of what contributes to their awesome reliability, even when highly modified.

    I recently had the rotating assembly balanced on a new engine build This is something that should always be done if you are putting in pistons/rods that are not very close to stock weight. Full engine balancing should be done internally by adding/removing material from the crank counterweights, then also with the harmonic balancer and flywheel/pressure plate combination.

    Fidanza Website wrote: 3. SHOULD I BALANCE MY NEW FLYWHEEL? – Since our product is CNC machined they are incredibly accurate. We do however recommend that you balance your new flywheel along with your new clutch pressure plate. This should be done by a reputable and competent machine shop.

    The flywheel/pressure plate balance on mine was 14 grams
    off. That's right, 14 grams! This is a HUGE imbalance for the rotating assembly not even accounting for the fact that it has such a large radius to work on. I can only feel bad the person who straps in a new clutch and one of these aluminum flywheels (or any flywheel for that matter) and does not get it balanced.

    I think it should be better publicized and eventually become public knowledge that this procedure MUST be done to assure longevity when replacing a flywheel and pressure plate.

  • #2
    Was the flywheel that shredded your engine balanced? That was an oem flywheel correct?
    85 Z31 6.0 LSX turbo 766whp/792wtq
    04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

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    • #3
      our crank pulleys are drilled to balance the crank, the pistons and rods are sold as matched sets by nissan.... so my question is which of the spinning wheels behind was the culprit?

      aftermarket flywheel?
      aftermarket clutch?
      aftermarket pressure plate?

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      • #4
        So then I should NOT use my under drive pulley?

        I wish I would have known this 8 months ago when I had my Fidanza flywheel center ring replaced & I installed my new RPS clutch. No balancing of the two was done. They did balance the flywheel I believe.
        378whp 445wtq
        http://mark86t.zmobiledetailing.com/.../v/Black+Hole/


        Z Mobile Detailing, Las Vegas, NV

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        • #5
          G-E wrote: our crank pulleys are drilled to balance the crank, the pistons and rods are sold as matched sets by nissan.... so my question is which of the spinning wheels behind was the culprit?

          aftermarket flywheel?
          aftermarket clutch?
          aftermarket pressure plate?
          Actually the pulleys are drilled to balance themselves only. The engine is internally balanced seperately from the flywheel/pp and crank pulley first.

          Flywheel and pressure plate are balanced as an assembly, but I can tell you the pressure plate is supposed to be pretty well balanced to begin with. The clutch disc is not balanced with the assembly because its orientation changes each time you engage/disengage.

          You'll notice stock flywheels are balanced. All I'm going to say is that you need to get an aluminum flywheel balanced with your pressure plate before use.

          Satan: the stock flywheel I had 'explode' was not balanced with the centerforce pressure plate I was using at the time.

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          • #6
            i never did that, but i guess i will in the future. can i just bring the flywheel and pressure plate to a machine shop that does balancing, or do they need to be mounted?
            Tom's Z31 300ZX Page
            NEz31s - The Northeast's Performance Z31 Club

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            • #7
              acabtp wrote: i never did that, but i guess i will in the future. can i just bring the flywheel and pressure plate to a machine shop that does balancing, or do they need to be mounted?
              Any good performance-oriented shop should be able to balance just the flywheel/pp for you.

              My understand of it is that with engines which are internally balanced like the VG, the flywheel and crank pulley can be balanced separately. With externally balanced engines, the flywheel and damper must be mounted on the crank for balancing.

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              • #8
                Re:

                Jason84NA2T wrote: the stock flywheel I had 'explode' was not balanced with the centerforce pressure plate I was using at the time.
                http://forums.beyond.ca/st/178859/skyrine-destruction

                Finally got that posted..

                Almost same looking that Jason's :nanan?re
                Jukka Kivinen - Europe / Finland - '88 Turbo 2+2 Targa
                Datsun Nissan Sports Cars of Finland
                http://www.z31turbo.com / http://www.z31na.com

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                • #9
                  Most engines are internally balanced which means a nuetrally balanced flywheel is needed. The note on their site and the fact that yours was not balanced makes me think they are skimping out on a good balancing job.
                  Chuck Stong
                  300+ Parts and Performance owner
                  http://www.300-plus.com
                  2002 ZCOT president and always active member

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                  • #10
                    Thankfully I am going to balance my entire bottom end when i get all the parts and send them to the machine parts.

                    I got the UR crank pulley, Z32 Wiseco pistons, Z32 Eagle rods, reman. crank (broke the original), and maybe a Fidanza flywheel. The crankpulley got me really gearing up for the bottom balancing, as it eliminated the harmonic balancer.

                    1986 300ZX Turbo.....1994.5 B13 Sentra LE.......1985 720 2wd......2014 Juke Nismo RS 6mt pearl white

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                    • #11
                      NissanEgg wrote: Thankfully I am going to balance my entire bottom end when i get all the parts and send them to the machine parts.

                      I got the UR crank pulley, Z32 Wiseco pistons, Z32 Eagle rods, reman. crank (broke the original), and maybe a Fidanza flywheel. The crankpulley got me really gearing up for the bottom balancing, as it eliminated the harmonic balancer.
                      Yes but still keep in mind that even with EVERYTHING THAT IS SPINNING on the bottom end being 100% FLAWLESSLY balanced, it still DOES NOT eliminate engine harmonics! That is the sole perpose of the harmonic balancer. Harmonic balancers do not help balance and engine that is not balanced correctly. They help to "dampen" engine harmonics.
                      85 Z31 6.0 LSX turbo 766whp/792wtq
                      04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                      Comment


                      • #12
                        Ok, well guys. Another local Z32 guy had his RPS flywheel and pressure plate balanced, per my recommendation. They found it was a STAGGERING 16 grams out of balance. I'm now of the belief that a balance of the fw/pp assembly should ALWAYS be done before installation of any aftermarket flywheel!!! Not doing so is just plain stupid.

                        SATAN wrote:
                        Yes but still keep in mind that even with EVERYTHING THAT IS SPINNING on the bottom end being 100% FLAWLESSLY balanced, it still DOES NOT eliminate engine harmonics! That is the sole perpose of the harmonic balancer. Harmonic balancers do not help balance and engine that is not balanced correctly. They help to "dampen" engine harmonics.
                        Just to clarify what you said... the harmonic balancer has nothing to do with rotational balance, except for the fact that it is balanced. Harmonic balance and weight are two very different things.

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                        • #13
                          Wow, I am glad I came across this thread! I am planning on a DXD clutch kit with a Fidanza flywheel setup here soon, so this is good to know. 8)

                          1985 Nissan 300ZX 2+2- My first Z, back in the family
                          1987 Nissan 300ZX Turbo RIP 4/87 - 4/28/2011
                          Under Construction: 1986 Nissan 300ZX NA2T Slicktop
                          Originally posted by Tempestas
                          Well, one of the t-tops wasn't latched real well... God only knows where that t-top flew off to at 150+ mph. Didn't scratch the car or anything, just a boom and it was gone. I sure as hell didn't stop to see where it went. I didn't see any stories on the news... so that's a plus.

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                          • #14
                            When i had my motor balanced, the shop told me that my new rods and pistons where like +/- 100 grams lighter that stock, and that they would have balanced they rebuilt assembly even if i hadn't asked for it. They did balance with the flywheel and pressure plate. And said that the old set up was heavily off balance but i forget by how much( ill look on the receipt).

                            If you plan on driving your car hard or at least want your money's worth and some longevity with your new parts I think balancing the rotating assembly is a must.

                            Originally posted by michaelp
                            The Industry is full of shit. Americans are morons and follow band wagons.
                            Illusions of Oasis. REPENT

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                            • #15
                              ballancing is a must if you go to aftermarket internals. with the stuff im using in the det im loosing almost 200g per rod piston combo. with that much of a difference it would shake itself apart in no time at anything over idle. im just curious on what you guys pay for your ballancing as i have gotten quotes from the engine lab and they want 500 to get it withing a 1/10g. another place i was refered to it was only going to be like 200 or so.
                              live fast,drive hard,and enjoy the ride!

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