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Thread: How To Avoid Machining

  1. #41
    Join Date
    May 2002
    Auckland, New Zealand


    The answer seems obvious to anyone with a milling machine - machine those old plugs out.

    No heating, cooling, bashing, laughable penetrants and frustration as experienced by those without a milling machine

    Please make sure the tappet guides are modified as others have said. I saw a 4.2 engine (rebuilt some months earlier) in which one or two of the guides came loose. The guide move upwards until the cam lobe rubs it on every revolution and fills the engine with cast iron dust!

    Be happy it is not a 4.2 engine, their larger bores are a bit too close together so the head gasket fails...

    Apologies to the OP - I missed the thread title, though I think it is wishful thinking
    Last edited by Peter S; 03-15-2019 at 09:18 PM.

  2. #42
    Join Date
    May 2002
    SE Texas


    Yes, but I would suggest a left hand drill bit. Every stuck screw that I drilled with a left hand drill bit came out before the drill went through. I don't know if it is the vibration, the heat, just the constant torque, or all of the above, but they ALL came out with a left hand drill bit.

    With such a large thread you may want to drill a pilot hole down the center first, perhaps 1/8" or so.

    Quote Originally Posted by gambler View Post
    drill em. those plugs can be really tight.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  3. #43
    Join Date
    Mar 2001
    Saranac Lake, NY


    And the winner is .... heat! Tried beating on the plug, first with a small ball peen hammer, then using a blunt tool in an air chisel. Made the plug look like it had a case of the mumps. Still wouldn't move. Then heated with oxy-acetylene until the steel started showing purple, then quenched with a wet rag. Did this twice. Tried the impact driver again, and -- success! There were three plugs, so on the second one, I left out the air chisel treatment. Success again. On the third plug, I just heated it once, quenched, and out it came. Threads are in good shape. So the theory that heating the plug crushes the rust/corrosion, reducing it's ability to resist shear seems to be true. Thanks for all the great advice & suggestions.

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