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Thread: Cadillac head bolts

  1. #1
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    Default Cadillac head bolts

    Many Cadillac North Star engines had aluminum blocks -small head bolts-AND FINE ThREADS. There is a good fix but you have to pull the engine out of the bottom of the car and do machining work cost $4000 How does any self respecting engineer live with himself? Have they no shame?


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  2. #2
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    Quote Originally Posted by Edwin Dirnbeck View Post
    Many Cadillac North Star engines had aluminum blocks -small head bolts-AND FINE ThREADS. There is a good fix but you have to pull the engine out of the bottom of the car and do machining work cost $4000 How does any self respecting engineer live with himself? Have they no shame?


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    No comment on the engineering of the bolts, but you can drop a Northstar out the bottom in a couple hours. I had one out and back in, in about 4 hours once.
    Last edited by paul463; 08-12-2019 at 12:03 AM.

  3. #3
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    Quote Originally Posted by Edwin Dirnbeck View Post
    Many Cadillac North Star engines had aluminum blocks -small head bolts-AND FINE ThREADS. There is a good fix but you have to pull the engine out of the bottom of the car and do machining work cost $4000 How does any self respecting engineer live with himself? Have they no shame?


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  4. #4
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    The question is whether they fail by themselves or only when shade tree mechanics over tighten them...
    They're probably designed for assembly anyway, not for repair.

  5. #5
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    Mar 2012
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    Go to youtube and search "northstar stud replacement" and you'll find lots of videos of this job. Many that leave the engine in the car...

  6. #6
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    May 2006
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    Reminiscent of the old VW's, very thick head bolts leading past the jugs and all the way down into the engine case and they were always pulling threads, very distinctive sound when taking off from a stop light (pop-pop-pop) as they were air cooled so the combustion gasses were directly injected into your ears...

    aftermarket made a series of attempts to correct, first crude method was a self tapping oversize head bolt, it was total hack but did work for awhile "most" of the time, it also threw chips into the engine...

    best method was to pull the engine all the way down and install "case savers" basically a thread inside a thread, you could then re-use your head bolts and never have another problem,,,

    newer engines were built with same size head bolt threads but used a small diameter bolt for the entire length, this allowed the stud to stretch during expansion rates instead of pull threads....

  7. #7
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    I had a similar thing happen back in the 60's with a Royal Enfield Constellation. The heads and barrels are held down by through studs into the crankcase. One stripped the crankcase thread, which was 5/16" BSF, not unexpected as the thread in the aluminium was on its last legs. I tapped the crankcase out to 3/8" BSF and got a local engineering firm to make me a special stepped stud. It stripped out the 3/8" in the crankcase straight away. I told the engineering firm's guy what had happened and he came up with the answer straight away, the expansion rates were incompatible. I was lucky to have enough metal in the crankcase to put in a 3/8" BSF Helicoil and they made me another stud out of austenitic high expansion steel which worked fine.

  8. #8
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    Quote Originally Posted by Wheels17 View Post
    Go to youtube and search "northstar stud replacement" and you'll find lots of videos of this job. Many that leave the engine in the car...
    In car repairs use steel thread-serts and stock head bolts. Still prone to failure . Permanent bullet proof fix is to drop engine,drill and tap and install STUDS. Edwin DIRNBECK

  9. #9
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    Feb 2011
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    Quote Originally Posted by paul463 View Post
    No comment on the engineering of the bolts, but you can drop a Northstar out the bottom in a couple hours. I had one out and back in, in about 4 hours once.
    A home shop guy like myself,cant safely drop an engine out the bottom of a car Dealers charge $4500..If you can do this in 4 hours,you can charge 1/2 the dealer rate and make $2000 a day.

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