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Head Bolts

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by longbedder, Oct 31, 2006.

  1. longbedder

    longbedder 1/2 ton status Premium Member

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    OK, here we go...:thinking:

    After extensive searching, I've found two camps regarding head bolts: 1) Clean em up and use the old ones, and 2) Buy new every time.

    The only reason for (2) would be if they are torque-to-yield bolts or damaged/corroded. The guys who post up that you are nuts if you reuse head bolts all claim that SBC's common to our trucks have TTY bolts, but this seems to be without substantiation.

    I have personally gone both routes in the past with SBC engines. I've torqued them all incrementally up to 65 ft*lbs. Never had a problem either way. I just picked up a set of FelPro ES72856 bolts, whose app. list includes up to 1997 SBC engines.

    The Fel-Pro bolt set (part number ES72856) appears in this catalog http://www.aaeq.net/catalog.pdf to be non-TTY.
    ----but----
    In this catalog http://www.gimmecarparts.com.au/search.cfm?StartRow=36&searchtext=&SearchCategory=TP1133 the same set is listed as TTY.

    So some folks aren't sure what they're selling.
    Most other catalogs don't say one way or the other. The instructions in the FelPro box say to follow OEM torquing instructions (big help).

    The GM shop manual says to torque to 65 ft*lb. Edelbrock says to do the same thing http://www.edelbrock.com/automotive_new/misc/tech_center/install/6000/60909.pdf.

    These would indicate that there is no such thing as a TTY head bolt properly used in our engines. We are certainly not putting a chromoly bolt of this size into a yield state using just 65 ft*lb - also, all TTY bolts are installed via specified turning angles, not torque specs.

    So, all this being what it is, it would seem that re-use of old bolts in good shape is fine. Just clean them well, lubricate them, and torque in the correct sequence up to 65 ft*lbs (starting at 40, then 55, then 65 ft*lb).

    Any thoughts?
     
  2. 55Willy

    55Willy 3/4 ton status

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    I have always reused head bolts. just clean them up and install them properly.
     
  3. sweetk30

    sweetk30 professional hooker Premium Member

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    do not much reuse the bolts that call for turn somany degrees of angle. those are bad ones.
     
  4. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    I'm impressed that somebody actually took the time to present an arguement with references that came out of books.......

    I re-use the old ones, if I ever get around to building an engine that I have a lot of money in I'll buy some new head bolts
     
  5. thedrip

    thedrip 1/2 ton status

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    I always figure if I didn't care enough to hot tank the block, or plastigauge the mains, why start doing it right and use new headbolts? lots of motors together that way, never had a problem. also never made more than about 250hp out of any one of them.
     
  6. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    i wouldnt re-use them in any motor that you were expecting to make more than 300hp out of, or something you knew would be wound up tight, repeatedly for extended periods of time.. they arent so expensive that if you were replacing the rotating assembly and doing a head job, why not?
     
  7. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    GM 12495499 Head bolt kit $30.

    I'm not sure the head bolts are TTY or not. But as an engineer, I have studied the effect of torque on bolts. So here's the thing, once you torque a bolt to torques in this range (65ft-lbs), what happens is the bolt stretches. This elastisity is what keeps the bolt in that position and provides the clamping force required to keeps the parts together. The reason it's so important in an engine application is that if the clamping force fails for even a fraction of a second, the head gasket becomes compromised. So providing consistent clamping force, hot or cold, humid or dry, is paramount.
    So, once you torque a bolt, it has lost some of it's elasticity. It won't be able to hold the same force for a particular torque. Say you bolt 2 pieces of metal together on the bench and torque it to 100ft-lbs. If you put a scale in between the 2 metals you'd be able to measure the force the bolt is providing. So you then loosen the bolt and re-torque it to 100ft-lbs. The force provided by the bolt is now less.

    So, what your doing by re-using head bolts is taking a chance. 9 times out of 10 it's probably fine.
     
  8. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    in ck5 engrish "add 5 lbs to each re-used bolt":haha: :haha:
     
  9. BadBob

    BadBob 1/2 ton status

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    That's ONLY if you exceed the yield strength.
     

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