what fly-wheel?

Discussion in 'transmission and Drive train' started by grumpyvette, Dec 23, 2011.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    hey grumpy?
    Ive built a pre 72 chevy 350 .060 over with a 383 rotating assembly, im sure its externally balanced because the guy sold me a balancer for a 400 but no flywheel, should I use a 400 flywheel in that situation? The rotating assembly is already installed and I cant find the part number card for it so Im at the end of my knowledge. Anything would help, thanks.

    when it comes to building an engine correctly with properly matched components it helps to have the total rotating assembly balanced by a trusted machine shop, and use of quality name brand matched components is seldom going to be a mistake!
    yes you'll tend to pay a bit more for a matched rotating assembly from someplace like SCAT\ and SFI rated flywheels and damper, but you'll also have a far lower chance of a mis-matched combo or odd imbalance issues or UN-explained parts breakage
    yes chances are almost 100% if your rotating assembly came balanced for a 400 counter weight damper that it will require a matching 400 counter weight fly wheel also, they come in 153 and 168 tooth size and its best to buy an SFI certified blow proof flywheel design, used with a lake-wood blow-proof bell housing or similar bell housing if you like having feet!
    theres links to the factory part numbers below but get a SFI certified fly wheel
    stock cast iron flywheels have a nasty habit of fragmenting at higher rpms if they heat crack, which ALL cast flywheels EVENTUALLY do if run hard and long enough, resulting in large jagged shrapnel thru the floor boards and windshield and everything between occasionally


    BTW the flat steel "TAN" in this picture, hard plate that is about 1/8" thick, that mounts between the flywheel and bell housing that helps protect the block from being damaged if the clutch or flywheel comes apart or loose at 6000 rpm
    yes it cost double what a cast flywheel costs...Id bet youll wish you paid the difference if a cast flywheel fragments and cuts your feet off? and yes 30-35 lbs is about correct for any car weighing 3000 lbs or more

    I tend to use mostly scat forged 4340 rotating assembly's
    but Ive used the 9000 series cast steel crank assemblies on less stressed engine builds with good results



    MCLEOD ,
    , RAM
    all have some decent flywheel & clutch products

    ATI Performance Products

    Trick Flow Specialties





    Last edited: Aug 16, 2016
  2. grumpyvette

    grumpyvette Administrator Staff Member

    " GRUMPY??
    Is my Flywheel scrap?
    My Flywheel has two areas that have some checking or slight surface cracks as seen in the pics below. Is this normal? can having it Blanchard ground take care of this or does it look beyond help?"


    there are 153 (about 12")
    and 168 tooth (about 14")
    fly wheel,
    but in every case the starter must be mounted, on the block with the correct matching bell housing on the block to correctly contact the flywheel SIZE your using

    on the plus side , when your working with the Chevy v8 engines SBC and BBC, if you select the correct two piece or one piece rear seal components, many aftermarket manufacturers of flex plates and flywheels to reduce manufacturing costs , build a neutral balance flywheel or flexplate and simply bolt on or weld on a weight to allow the same basic part to work with both potential combos
    Counter Weight Kit General Motors Flywheel (1A/2C/3C/4C)

    Fits Externally Balanced Applications

    1986-1999 SBC

    1970-1990 BBC

    1991-1997 BBC

    1970-1980 SBC 383/400

    Default SBC Flywheel & Flexplate part numbers

    Small Block Chevy Flywheel Part Numbers
    Part # DIA. Teeth Comments
    3991406 Flywheel, LW Nodular Iron for HD 10.5" Clutch
    3991469 14" 168 two-piece seal, internally balanced
    3986394 14" 168 400 External balance, two-piece seal
    10105832 14" 168 86-later, one-piece rear seal, ext. balance
    14088671 12.75" 153 86-later, one piece rear seal, int. balance
    14085720 12.75" 153 Lightweight (15 lbs.), nodular iron, two-piece seal, int bal Will work with a clutch diameter of 10.4" only. Crank flange bolt pattern is 3.58". Will work with a clutch diameter of 10.4" OR 11.0". Crank flange bolt pattern is 3.0"
    14088646 12.75" 153 86-up, Lightweight (15 lbs.), nodular iron, one-piece rear seal, ext bal
    14088648 14" 168 86-up, one-piece rear seal, ext. balance
    14088650 12.75" 153 86-up, one-piece rear seal, ext balance Will work with a clutch diameter of 10.4" only. Crank flange bolt pattern is 3.0"
    10174482 89-up with six-speed m/t, requires starter (10455709)
    Common clutch sizes are: 10.4", 11.0", and 11.85". Some flywheels are drilled for two different clutch patterns.
    12.75" are usually 153 tooth and the other larger 14" diam. are 168 tooth flywheel or flex plate designs, the larger 14"/168 tooth designs fit the much stronger 11" clutches.... obviously the 14" can use a larger clutch, but require a larger bell housing that is why some stock bell housings won,t fit the larger fly wheels and of course the starter used must match


    keep in mind any serious performance application is best served with SFI certified billet flywheel,
    clutch assembly and a blow proof bell housing
    Small Block Chevy Flexplate Part Numbers
    Part # DIA. Teeth Comments
    471529 12.75" 153 Two-piece seal blocks, int balance
    471578 14" 168 400 ext. bal, two-piece rear seal
    471598 14" 168 Two-piece seal blocks, internal balance
    10128412 12.75" 153 86-up, one-piece rear seal ext. balance
    10128413 14" 168 86-up, one-piece seal, extra thick, HD, ext bal
    10128414 14" 168 86-96, one-piece rear seal, ext. balance
    14088761 14" 168 89-up 350 HO, one-piece rear seal, ext. bal.
    14088765 12.75" 153 86-up, one-piece rear seal, ext. bal.
    14088767 14" 168 89-up 350 HO, one-piece rear seal, HD, ext. bal


    well as Im sure a few of your friends have been sure to mention, you have a choice too make here, you can save a few bucks and reuse the obviously damaged fly wheel knowing full well that theres a significant chance that it will fragment throwing large jagged chunks of shrapnel thru the cars interior at some point.
    the surface of the flywheel appears to have little radial cracks: these are a indicator the fly wheel might be prone to coming apart under high rpm stress loads, like a quick shift under load...yeah! I know you know someone who has run a flywheel like that for years with zero problems.......its your feet and its just a mater of time.....
    having high velocity chunks of cast steel pass thru your car, with a good chance you'll loose your feet in the process as the shrapnel exits the car, won,t be fun!
    or you can upgrade to a billet flywheel and a blow proof steel bell housing and have significantly reduced the chances of getting a nick name like "STUMPY", "TOE-LESS JOE" or "SHORTY"

    personally Id suggest investing in a good lakewood blow proof bell housing and SFI billet clutch and flywheel
    use of a block plate and a blow proof bell housing ,helps prevent your feet from being cut off if the clutch or flywheel explodes, and
    can frequently prevent major damage to an expensive engine block,
    and avoid thousands of dollars in machine work cost on a replacement block.
    use of SFI certified clutch components significantly reduces the chances of parts failure.

    SFI chevy flywheels



    its a great idea to use the proper GRADE #8 fasteners as they are significantly stronger than the average grade 5 hardware store bolts


    ONE REASON I TEND TOO STRESS THE USE OF both A LAKEWOOD BELLHOUSING AND A SFI RATED BILLET STEEL FLYWHEEL, AND A SFI RATED PRESSURE PLATE , is that over the last 45 or so years Ive personally seen the results of at least 6 cases where clutches or flywheels came apart at higher rpms, the results can nearly cut the car in half without a blow proof type bell housing

    trust me when I say it gets far more expensive, to repair a car when a blow proof bell housing doesn,t limit the damage

    and thats not counting the surgery required to repair or amputate ankles or toes etc, as a 10 lb chunk of flywheel coming apart at 6000rpm WILL go through the floor, doors or dash and windshield

    read thru these

    http://www.jegs.com/i/JEGS-Performance- ... Id=1359671

















    Last edited by a moderator: Apr 5, 2017
  3. philly

    philly solid fixture here in the forum

    wow that first picture is some serious carnage!

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