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Change Headbolts/studs from 3/8 to 1/2" on a -39 212 splasher engine
  • Krille
    Posts: 42Hitchhiker
    Hello!
    The studs in my engine block for the head keeps breaking at low torque, one of them broke in the block aswell, so it need drilling.
    I was thinking about changing them to 1/2" studs instead if that is a doable conversion? The block should have enough thinkness what it seems like, but will the thickness in the top hold up for 1/2" holes instead of the holes for 3/8" studs?
    Otherwise the operation seems to be quite simple.
  • ET8conv
    Posts: 119Expert Adviser
    How tight are you are you torqueing them ? The spec is only 45lf/ft and the original studs should be able to handle that amount.
  • ET8conv
    Posts: 119Expert Adviser
    sorry that should read 45lb/ft.
  • Geoff C., N.Z.Geoff C., N.Z.
    Posts: 2,270Platinum Member
    I would definitely not recommend drilling out to half inch. These old blocks don't have much intestinal fortitude, and by drilling the head, and putting 1/2" studs you are going to weaken it even further, and will not be able to hold head gaskets. Fit a new set of 3/8" studs, and keep the torque to 40 lbs, and you should not have any trouble.
    If you're stuck in a hole, stop digging.
  • Tallent RTallent R
    Posts: 1,574Platinum Member
    You may even have a bad torque wrench . If its the clicker type in particular.
    Roger
    Retired Tech.
  • Krille
    Posts: 42Hitchhiker
    I have tested with two dofferent wrenches, good quality. They snap at around 35-40, but then i will startt with changing all bolts and nuts that might need re-tightening to a higher grade and see if it holds up better.
  • Marconi
    Posts: 549Platinum Member
    It may be overkill but I'd make sure to use grade 8 studs and use hardened flat washers under the nuts.