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Technical How much torque to turn over a V8 by hand with no plugs

Discussion in 'The Hokey Ass Message Board' started by blowby, Oct 15, 2015.

  1. blowby
    Joined: Dec 27, 2012
    Posts: 8,661

    blowby
    Member
    from Nicasio Ca

    Got a stock SBC that was stuck, not bad, one night soak and it broke free and can turn it over with a 1/2" ratchet on the balancer bolt but slow on the starter. Good connections, cranking amps etc.. Before I pull the starter I was just wondering if anyone knows how much torque it should take, roughly, with a torque wrench on the balancer bolt to turn it. Plugs out.
     
  2. oldolds
    Joined: Oct 18, 2010
    Posts: 3,407

    oldolds
    Member

    I don't know the answer but I think I remember reading that in the How to Hot Rod a Small Block book.
     
  3. Most used engine can be turned by hand on the crank, flex plate
     
  4. I always went with 40 ft-lbs of torque to spin a new engine over.
     
    scrap metal 48 likes this.

  5. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 3,093

    FrozenMerc
    Member

    Are you sure the starter is OK??? I once built a 351W that went together very tight. Probably took 80 ft-lbs or more to turn it over by hand at the balancer. However with new cables and a starter, it spun over just as quickly as a tired old 300,000 mile motor.

    Most OEM start motors produce 5 to 10 hp, which equates to 10 to 20 ft-lbs of torque at the starter gear, depending on rpm and amperage. Multiply that by the typical 15:1 to 20:1 gear ratio between the ring gear and starter gear, and you should see 150 to 400 ft-lbs of torque at the flywheel. If it takes 150 ft-lbs to turn over a 350 with no plugs, you have a bigger problem.
     
  6. My freshly assembled SBC took 25 foot pounds.

    I've heard of race motors that were even less.
     
  7. blowby
    Joined: Dec 27, 2012
    Posts: 8,661

    blowby
    Member
    from Nicasio Ca

    Thanks guys. I can turn this with two fingers on a 1/2" ratchet, probly less that 25 ft lbs, so starter's coming out.
     
  8. Moselli
    Joined: Feb 16, 2009
    Posts: 107

    Moselli
    Member

    You may want to put a volt meter on the battery and see what the voltage drop is when you try to crank the motor. Might give you an indication of whether you have a starter issue or a bad battery... Good luck.
     
  9. Yeah I'm guessing its an electrical issue.
     
  10. blowby
    Joined: Dec 27, 2012
    Posts: 8,661

    blowby
    Member
    from Nicasio Ca

    I believe i have found the problem. Surprised it spun at all. 1015151059.jpg
     
    scrap metal 48 likes this.
  11. Aw heck, man. A little super glue and that thing will be good as new. :D
     
  12. '51 Norm
    Joined: Dec 6, 2010
    Posts: 829

    '51 Norm
    Member
    from colorado

    I'm sure glad that has never happened to me. Except for that one time, maybe and I don't want to talk about that.

    Good find; it is nice the actually find a problem.
     
  13. czuch
    Joined: Sep 23, 2008
    Posts: 2,688

    czuch
    Member
    from vail az

    That's too easy, I'd look further into it.
     
  14. BJR
    Joined: Mar 11, 2005
    Posts: 9,817

    BJR
    Member

    That would really bind things up, I'm suprised it turned over at all!
     
  15. 40fordtudor
    Joined: Jan 3, 2010
    Posts: 2,503

    40fordtudor
    Member

    It'll buff out, tho-----
     
  16. blowby
    Joined: Dec 27, 2012
    Posts: 8,661

    blowby
    Member
    from Nicasio Ca

    I used to have piles of this stuff laying around. Had to go to the bone yard, bought a rusty core for $20, swapped the nose, off and running. Caused by backfire I suppose.

    Oh, notice the shorter than typical solenoid? Had to swap the fork and piston into the new housing.
     
  17. Gene Boul
    Joined: Feb 9, 2006
    Posts: 805

    Gene Boul

    I don't think thats the problem...suggest you remove engine, trans and tachometer!
     
  18. tubman
    Joined: May 16, 2007
    Posts: 6,916

    tubman
    ALLIANCE MEMBER

    I tried my 255' Merc flathead today and saw 25-30 ft-lbs.
     

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