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Hybrid head bolt torque; which spec do I use?

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  • #1

    Hybrid head bolt torque; which spec do I use?

    Alright so as I said in the other thread I'm starting to put things back together now, and just when I went to put the first head on, I realised something... What head bolt torque rating am I supposed to use???

    My engine originally was a 3100 L82 and the specifications have the head bolt torque as 33lb*ft + 90 degrees.

    But I'm swapping LA1/LG8 (3400/00+ 3100) stuff on to it--heads and intake manifolds. But the torque specs for the LA1 and LG8 is 44lb*ft + 95 degrees!

    That seems like a bit of a difference to me. Which should I be using?

    The head bolt set part number for all three engines is apparently the same (so the head bolts are the same).

    My block should be the same as an LG8 (00+ 3100) block, right?

    My heads (are now) the same as LG8 heads.

    So should I use the LG8/LA1 specs for torquing the head bolts or my original specs? I searched quite a bit, but interestingly I found no mention of this question/answer anywhere...
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  • #2
    I've never done that job before... so take my advice with a grain of salt.

    If you can confirm that your block is in fact the same as the 00+ engine... and that your head bolts, gasket, and heads are the same... then the answer is obvious. You'd go with the '00+ specs.

    If the blocks are somehow different... then it's a toss-up. I'd probably split the difference.

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    • #3
      Id think the spec is more geared to the head gasket and the bolts used rather than what kind of head and block you have. Use whatever year spec the headgasket was purchased for.
      I modify stuff

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      • #4
        Originally posted by GPXSS View Post
        Id think the spec is more geared to the head gasket and the bolts used rather than what kind of head and block you have. Use whatever year spec the headgasket was purchased for.
        Hmm but it's the same gasket for both an L82 and an LG8 (large port) 3100... I'm just gonna use something in the middle like 37lb*ft I think...

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        • #5
          When I built my hybrid, I used the torque specs for my head, which were 33 + 90*, never had a problem with that on my turbocharged engine.

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          • #6
            Thanks Raven I guess I'll just do that then

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