Head Bolts

Discussion in 'Engine & Performance' started by Enigma346, Jan 9, 2020.

  1. Enigma346

    Enigma346 Full Access Members

    Age:
    35
    Posts:
    81
    Likes Received:
    7
    Joined:
    Apr 12, 2018
    Location:
    Hertford, NC
    So when replacing my head do I need new head Bolts or can I just reuse the ones that are there already?

    2003 Ford Expedition XLT
    4.6L
    4x4
     
  2. BlackCoffee

    BlackCoffee Active Member

    Age:
    63
    Posts:
    34
    Likes Received:
    10
    Joined:
    Mar 26, 2019
    Location:
    SOMD
    New. Head bolts are torque to yield. You set torque in two stages and then add 90 degrees. A good ($140) electronic torque wrench is great for this.
     
  3. joethefordguy

    joethefordguy Full Access Members

    Posts:
    218
    Likes Received:
    52
    Joined:
    Apr 10, 2017
    Location:
    Texas
    I am ignorant. what does "torque to yield" mean?
     
  4. BlackCoffee

    BlackCoffee Active Member

    Age:
    63
    Posts:
    34
    Likes Received:
    10
    Joined:
    Mar 26, 2019
    Location:
    SOMD
    Torque to yield is when you tighten a bolt beyond it's yield point. In essence, you stretch the bolt. This happens when you tighten to a torque value and the add some angle, in most cases another 1/4 turn or 90 degrees. Since the bolt has actually stretched, reuse to a torque value is unreliable. So, any bolts that are torque to yield can only be tightened once, then they must be replaced.
     
  5. TobyU

    TobyU Full Access Members

    Posts:
    2,025
    Likes Received:
    695
    Joined:
    Apr 5, 2013
    Location:
    Ohio
    It means the manufacturer wanted to sell us more parts and rip us more in the future.
    In the old days, around pre 1983 or so they were not TTY.
    We reused them many times on many engines without issue.
    Then they concocted some convoluted reasoning and convince some people that a TTY at higher torque was better than a stronger bolt at lower.
    They "might" have made them smaller diameter and compacted things a little more by doing this but I still would have passed!
    We used to buy ARP head bolts for muscle car engines and they were way beyond factory that we often reused. The ARP were used repeatedly without concern by most.

    SO now when you do a head gasket(s) you get to spend 26-50 more for a set of bolts or risk one snapping when you torque them to specs.
     
  6. Trainmaster

    Trainmaster Old School Member

    Age:
    54
    Posts:
    1,768
    Likes Received:
    871
    Joined:
    Jun 17, 2017
    Location:
    Rockaway Beach, NY
    Buy new head bolts.
     

Share This Page