Torque for 1/2" headbolts.

GrimGreaser
GrimGreaser Senior Contributor
in HUDSON
I know... asked and answered a gazillion times, but my searches didn't really answer my question. I know 75-80 ft-lbs is for the 7/16" head bolts... is it the same for the 1/2" bolts? I plan to use Belleville disc springs to maintain preload on the head-block joint. A 1/2-13 bolt torqued to 80 ft-lbs gives a bolt force of about 8500 lbs. For the Bellevilles to be effective, their fully flat spring force needs to be close to the required bolt force. 1/2" disc springs can get expensive, so I'm trying to be economical on the number I need. Thanks guys!

Comments

  • Geoff
    Geoff Senior Contributor
    It is far better to just use  hardened steel washers under the head bolts than any type of spring washer. .  The 1955 Hornet 6 specs are for 75-80 lbs, and these had 1/2" bolts, so it looks like the same applies regardless of bolt size.   Any tighter and you are in danger of distorting the block. 
  • GrimGreaser
    GrimGreaser Senior Contributor
    Thanks Geoff. I figured as much, but couldn't quite remember. I'm using the Bellevilles to reduce the loss of clamp load in the joint as everything settles over time. Extra insurance the joint stays tight.
  • Ol racer
    Ol racer Senior Contributor
     I agree, no more than 80lbs using large Dia Grade 8 Washers with larger 1/2" SAE Wheel Nuts..I know because I ruined a Deck by exceeding the 80lb Torque trying to seal on one motor..... (Currently, I use large HEX NASCAR Wheel Nuts requiring 1 1/16" socket).
  • Geoff
    Geoff Senior Contributor
    I'm not familiar with the type of washer you mention, but hardened steel washers will not compress and will give you a true torque reading.  The only thing that is likely to   settle is the head gasket.   and of course there is a difference with alloy and  iron heads,  - alloy must only be torqued  cold,  and iron hot.   
  • GrimGreaser
    GrimGreaser Senior Contributor
    For those interested, document attached.

  • keithfullmeryahoocom
    keithfullmeryahoocom Expert Adviser
    Good info.   Thanks for posting...k

  • Geoff
    Geoff Senior Contributor
    It's all very technical, but I see no reference  regarding using them for an iron head, only flanged joints.    
    Geoff 
  • GrimGreaser
    GrimGreaser Senior Contributor
    Geoff, that analysis is valid for all bolted/screwed joints and connections. I learn a lot here, I'm just trying to add to everyone's knowledge.
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