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Thread: How much to turn?

  1. #1
    Member CRAFTSMAN
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    How much to turn?

    I am building a 400 sbc.I remember a long time ago a engine builder Iknew said it should take just so much torque to turn a short block assembly.I was just wondering if anyone has heard of this,and just what it should take to turn one? Using my torque wrench on crank snout it takes between 18 / 20 ft lbs.

  2. #2
    Senior Member RACING JUNKIE curtisreed's Avatar
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    Is that the break away torque or the turning torque? Every engine is different based on ring tension, ring thickness, cylinder diameter, assembly lube used, double or single lip seals. You see my point. It's not always just a straight forward number to cover them all.

    That said if that is your break away torque it is probably just fine for a street / bracket type engine. JMO

    Curtis

  3. #3
    Member CRAFTSMAN
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    Yea I guess it would be break away torque. I see your point last time it was a 355 different bores,rings,ect. Thanks

  4. #4
    Senior Member RACING JUNKIE
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    Quote Originally Posted by curtisreed
    Is that the break away torque or the turning torque? Every engine is different based on ring tension, ring thickness, cylinder diameter, assembly lube used, double or single lip seals. You see my point. It's not always just a straight forward number to cover them all.

    That said if that is your break away torque it is probably just fine for a street / bracket type engine. JMO

    Curtis
    I agree 100%
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  5. #5
    Senior Member DYNO OPERATOR
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    turning

    BBC short block only turning torque around 25-30 with std. tension 1/16 rings.

  6. #6
    Senior Member EXPERT BUILDER
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    Cylinder finish plays a key role in both break away and turning torque.

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  7. #7
    Senior Member RACING JUNKIE
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    What's the point? All the engine builders that I considered as "good ones' advocate turning the crankshaft assembly through several rotations so that the rings (in completely dry cylinders) will begin to seat.

    Most modern racing engine builders will tell you that after about 5 revolutions, if you honed the cylinders correctly and they're straight, 75% of the "break in" or seating of the rings will be accomplished. The last 25% requires heat and compression to finish the job . .

    But that's what I've been told over the years and some of you may have different ideas or mentors . .

    And once you have turned your crank assembly four or five revolutions the torque readings will (or should) change . . even the breakaway will be affected . . The numbers? Whatever you end up with, but it certainly shouldn't require MORE torque to any degree . .

    And without the full assembly, the crank should spin by just twisting the rear crank flywheel flange with your fingers . . If it doesn't, your bearing clearances are too tight!

  8. #8
    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    Quote Originally Posted by roadkill2

    And without the full assembly, the crank should spin by just twisting the rear crank flywheel flange with your fingers . . If it doesn't, your bearing clearances are too tight!
    Unless it's damn cold in the clean room and your assembly lube is the consistency of grease ((((( :shock: )))))
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  9. #9
    Senior Member RACING JUNKIE
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    Well, Yeah . . !

    heh, heh, back in the day, I had a buddy who built 392's for a couple of the T/F FEDs in the area and he assembled them with 50 weight. On a cold day you couldn't turn the damned things over with a 6' cheater pipe on your breaker bar . . First time he used white lubriplate on one he went back and took it apart to recheck the bearing clearances. . he said , at first he thought he had left the bearings out of it . . .

    When I think of all the dumbassed stuff we used to do, because some hot shoe told us that's what he did, I wonder how I kept from either shooting myself for being so damned stupid or grenading everything I ever touched . . . Very flat learning curve . . heheheheheh

  10. #10
    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    I learned later $$$$$ in life not to believe EVERYthing another 'racer' told you. They'd lead you up the wrong stream and laugh their a$$e$ off at your expen$e . Funny now but shor weren't then ! :roll: ops: ops: ops:
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