Flywheel Bolt SIZE???

Discussion in 'U-shift em' started by sriley531, Apr 22, 2014.

  1. sriley531

    sriley531 Excommunicado

    Can anyone confirm the size of bolt I need to secure a flywheel to the crank on a 455? I did a search and found all the "TA has them" comments. Thats all good and well, but Im really itching to mock this thing up so I can indicate in the scattershield and order offset pins (if needed), and sitting on my hands waiting on them to crawl in from Arizona isnt on my to do list. I'm hoping to source some local just for mockup purposes, and my last few orders from TA havent exactly showed up lickety split, so its a timing thing. :rolleyes: Can anyone give me an actual SIZE?? It looks like either a 7/16" or 1/2" fine thread, but i'd rather not go guess and buy a bunch of different ones to see what fits.
     
  2. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    I would guess 1/2-fine thread. What I would DO is take a 5/8th socket to the hardware store and find the bolt that fits that with a fine thread because I am sure it's a 5/8th socket :)
     
  3. wkillgs

    wkillgs Gold Level Contributor

    Just checked... it's a 7/16"-20, with 5/8" head.
    Also fits the Nailhead crank.
    I bought Big Block Chev ARP bolts for my Nailhead:

    Part Number: 100-2801
    Bolt Thread size: 7/16"-20
    Under Head Length: 1.000"
    Rating: 180,000 PSI

    They were too long and bottomed out against the block! had to grind them shorter. Would've been a disaster if I hadn't caught that!
    I somewhat recall a post here mentioning the same length issue when used on a 455.
     
  4. sriley531

    sriley531 Excommunicado

    Yeah, just last night I went to Lowes and bought some 7/16-20 bolts. They were grade 5 cheapies, but I was only using them to hold the flywheel while I indicated in the bell housing (or tried to anyway, but thats another story...:af:). They only had 1.25", so I spaced them with some washers.

    Do you recall how much you had to grind off? ARP 330-2801 are 7/16-20x.875". Wondering if that would save the hassle.
     
  5. 69GS400s

    69GS400s ...my own amusement ride!

    I'm no mechanic ( I only play one in my garage ) but couldn't a cutoff wheel or grinder create enough heat whilst whacking said bolt to reduce its strength ?
     
  6. sriley531

    sriley531 Excommunicado

    From a metallurgical standpoint, it absolutely could be possible. The caveat being without knowing more information on the material properties with which these bolts are made from and what type of heat treat or other hardening processes they are subject to during manufacturing, its harder to determine if any significant effect would be had on tensile strength, and to what extent (how much of the material) would be changed. For all intents and purposes, I doubt you're really greatly increasing your risks of breakage to the point of routine usage causing a catastrophic failure, but I obviously don't have any quantitative data to prove one way or the other so its purely speculation on my part.

    Condensed version, "Ah, prolly not too bad but who knows..." :Do No:
     
  7. 69GS400s

    69GS400s ...my own amusement ride!

    good thing you didn't start talking about The differential-depth method and subtracting out errors associated with the mechanical imperfections of the system, such as backlash and surface imperfections

    .. or, Hey !! Hit it with a hammer and see if it breaks :Do No: If not, it must be good
     
  8. sriley531

    sriley531 Excommunicado

    Jeeze Alan, ya ain'ts gots ta go gettin all testicle bout it....
     
  9. Taulbee2277

    Taulbee2277 Silver Level contributor

    That is my advise to him most of the time. Then he starts talking and I hear birds chirping ;)
     
  10. sriley531

    sriley531 Excommunicado


    :moonu::moonu::moonu::moonu::moonu::moonu::moonu::moonu::moonu::moonu:
     
  11. wkillgs

    wkillgs Gold Level Contributor

    I took off about 1/8" for my Nailhead..... your 455 may differ! TA Billet flywheels are supposedly thicker than stock, 1" may be fine for those.

    If you keep the bolt cool while you grind, you won't kill the heat treat. Grind a little.... dip it in water to cool, grind some more, cool again.
    A good rule of thumb is: if your fingers catch on fire while grinding the bolt, the heat treat of the bolt could be affected...
     
  12. sriley531

    sriley531 Excommunicado

    Well, as it turns out the 1" bolts are too long BARELY. They just touch when torqued all the way, enough to put a small mark on the paint but not go all the way through it. Looks like a pinch of love from the grinder is in order.
     

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