5.9 magnum header bolts

Discussion in 'Magnum Engine Swaps' started by 05harley, Apr 15, 2018.

  1. 05harley

    05harley Member

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    Has anyone drilled the 5.9 magnum heads out to receive 3/8" header bolts??? My heads are off a 97 engine and came with 5/16" bolts----my headers came with 3/8" bolts which makes a lot better sense---so I am hoping to drill the heads an tap for 3/8" thread----just wondering if other people have done this successfully?????
     
  2. goldduster318

    goldduster318 Overzealous Car Modifier

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    They sent you the wrong bolts, they should be 5/16"
     
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    • 05harley

      05harley Member

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      I understand the wrong bolts------just wondering if there will be issues with drilling the heads----are should I just go pick up some 5/16 bolts---Tx
       
    • goldduster318

      goldduster318 Overzealous Car Modifier

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      I can't even think why you'd even consider drilling the heads (my original 1970 engine, the 94 magnum heads I had, and my edelbrocks) are all 5/16", when you can just get the right bolts.
       
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      • Burlapen

        Burlapen Well-Known Member

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        I would be afraid of clearance from the bolt head to the pipe more than anything. Most 3/8 bolts will probably have at least a 7/16 head. It gets tight on a couple of tubes.
         
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        • TrailBeast

          TrailBeast Slightly Twisted Member

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          Yea, like where some of the tubes cross back over the top of the bolts.
          They are already tight with 5/16 (which I have never had a problem with 5/16)

          A person could get away with it with 3/8 allen bolts, but cutting the allen wrench down to get in under the pipes is going to be mandatory.
           
          Last edited: Apr 19, 2018