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Flywheel modification question

Discussion in 'The Hokey Ass Message Board' started by Window Licker, Sep 24, 2012.

  1. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    I bought a t56 to put in my hot rod, the only problem is i need an 1986 and newer crank bolt pattern to bolt the necessary flywheel to. i know you can buy a flywheel for the t56 and the early crank bolt pattern. my questions is: can i have a machinist re drill a stock flywheel for the t56 to fit the early bolt pattern? or maybe slot the original stock t56 flywheel bolt holes to the bolt pattern diameter needed? or take a early center and put it in the t56 flywheel? currently i have a worn out early bolt pattern flywheel and a good t56 flywheel, plus a machinist friend who works for little to nothing. are any of my ideas mechanically impossible or unsafe? im worried about the flywheel not being perfectly centered, but i believe they center on the crank not the bolts. i also dont want to cause imbalance. any thoughts would be great thank you.
     
  2. Pete1
    Joined: Aug 23, 2004
    Posts: 2,124

    Pete1
    Member
    from Wa.

    Some flywheels can be redrilled to fit other applications. The fore and aft distance needs to be fairly close also. On some the holes will overlap too much to be safe.
    The only one I can tell you for sure is a SBC can be redrilled to fit a flathead Ford but the starter mount needs to be modified also.
    Something to consider on your application.
     
  3. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    thats the thing the t56 flywheel has a ton of meet before you get to the clutch mating surface.

    good idea on the starter thing i didnt think to check that.
     
  4. Clarks67
    Joined: Jul 22, 2012
    Posts: 13

    Clarks67
    Member

    The early SBC, and the later flywheels are balanced different. You can't put the later one on the early motor without causing a vibration.
     

  5. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    could a driveline shop balance it to whatever spec is needed? theres a good shop in my area that i think could probably do the work. ill have to call in the morning
     
  6. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus


    I would think your machinst friend could also mill the balance weight off, and then an AUTOMOTIVE machine shop would do the actual balancing (or just have them do the entire job). As long as the "distances" as far as the starter motor and clutch assembly goes, I would redrill, not elongate, the existing holes. Butch/56sedandelivery.
     
  7. squirrel
    Joined: Sep 23, 2004
    Posts: 52,836

    squirrel
    Member

    The early 350 has neutral balance, so they'd have to rebalance the flywheel to neutral.

    I don't know if it would work or not...it would be worth looking into and see if there's enough meat where it needs it.

    You would probably want to drill new holes between the old ones. The dowel hole will mess you up too.
     
  8. Clarks67
    Joined: Jul 22, 2012
    Posts: 13

    Clarks67
    Member

    A good machine shop might be able to. It may be easier and cheaper to get anther flywheel, and get the correct clutch disc for the T56 input spline.
     
  9. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,907

    gimpyshotrods
    ALLIANCE MEMBER

    So I'm assuming that this is an LT1 T56 from an F-body, with the weird hydraulic pull clutch. If it is, you are better of ditching the pull clutch setup, and replacing it with an adapter from McLeod, a conventional bellhousing, clutch/flywheel assembly, extended pilot bushing, and an LS1 input shaft.
     
  10. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    actually id prefer to stick with the pull off set up. it works out much better in the space i have available.
     
  11. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    if i can get to the right bolt pattern everything else will be stock, stock clutch stock pressure plate with stock flywheel
     
  12. Clarks67
    Joined: Jul 22, 2012
    Posts: 13

    Clarks67
    Member

    As long as the machine shop can balance the flywheel to zero balance, the area around the bolts has enough meat left where the bolts are it would probably work. It would be a good idea to measure the inside diameter of the flywheel where it slips on the crank to be sure it has the correct clearance. It should be a snug fit. If it is loose that could cause a vibration.
     
  13. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    thats my thoughts exactly
     
  14. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I redrilled a GMC 6 bolt flywheel to go on the early 4 bolt crank. Worked fine for several years at Bonneville, Drags and El Mirage. Drilled a four bolt Plymouth flywheel to 8 bolts and also drilled and taped the crank to fit. Worked great. Cut the weight off a late Ford 302 flywheel to use on my new banger. Took it to an automotive machine shop and had him drill it to a 0 balance. My removing the weight didn't quite make it perfect. I also once turned the OD of a 392 flywheel to fit a Pontiac ring gear so it would fit in the blowshield I was using. That worked also. So i would say you can modify your flywheel to work if you use a little common sense.
     
  15. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    based on this im pretty positive it can be done, i think the only thing that would hold me back at this point its if the outside diameter are different and its too small to mate with the starter
     
  16. squirrel
    Joined: Sep 23, 2004
    Posts: 52,836

    squirrel
    Member

    As far as I know there are only two sizes of flywheels, and even if it's an oddball size you could just get a starter to match the flywheel. The starter bolt holes seem to have stayed in the same place all these years.
     
  17. Window Licker
    Joined: Apr 18, 2009
    Posts: 287

    Window Licker
    Member

    Thats what i thought but im not up on lt-1 stuff
     
  18. Dawai
    Joined: Oct 1, 2007
    Posts: 263

    Dawai
    Member
    from North Ga.

    26T spline? use a early Rock crusher (M22?) flywheel-disc-pressure plate. The spline was the same if I remember.

    Fit it all on the floor, unless you like seeing the underside of the car. My swap has been in and out so much I think I've had sex with it.
     
  19. I modified a Y/block F/wheel to fit a 365 caddy.Both are 6 bolt mount,just bored out the centre to suit the Cad crank then drilled the 6 mounting holes which were a larger PCD to suit.Boring to suit the Cad spigot cut through the original Y/block bolt holes and the new holes fit between the old so theres plenty of meat left.
    Then machined off the ring gear and brought the dia down to suit the ring gear off a Cad fluid drive plate(flex plate)leaving a small seat for the ring gear to position it then fit and tacked it in place.I use the original starter and redrilled the face to suit an 11" clucth setup.Made a bush for the rear of the crank for the input shaft and had it all balanced.The Y/block flywheel is a good weight for the Cad motor also,something else to think about.
     

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