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Thread: Removing head bolt studs in aluminum case

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  1. #1

    Default Removing head bolt studs in aluminum case

    I'm changing the right case on my '66 Ducati 100 and I'll have to transfer two of the head bolt studs from the old case to the new case. The cases are aluminum. I tried to remove one of them on a frozen engine and it snapped it right off.

    I've soaked the other ones for two weeks with PB Blaster.

    Anyone have any safe recommendations for taking out the studs? Heat? if so/how much? I've heated exhaust bolts in cast iron car manifolds and have had good success, but I've never done aluminum.

    Thanks!
    John
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  2. #2
    Join Date
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    If Ducati was using common practice at the time the studs are an interference fit and not intended to be removed. Heat will work but it needs to be at least 300 degrees+. Heat the assembly in an oven if possible, although a torch can be used with care. I doubt the PB blaster will touch it...
    If you are using that left case you are in for some fun!
    Last edited by Rubone; 05-06-2020 at 07:08 PM.
    Robbie Knight Amca #2736

  3. #3

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    Could you elaborate on what you mean by an interference fit for a head bolt? Is it something like the stud on a kickstarter shaft?

    Here's a shot of the used case I will be installing (after I do a clean up). It has the studs removed, but I bought it this way.

    John
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  4. #4
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    It means the two parts were machined for a planned overly tight fit. Common on studs in aluminum where there was no reason to remove them.
    Robbie Knight Amca #2736

  5. #5

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    Interesting, thanks Robbie. Maybe that's what I thinking is a "press fit". I never though it might apply to a threaded bolt.

    I am going to examine the used case that I will use to see how easily a threaded stud will go into it, then carefully try to remove the studs from the seized engine I have. I haven't been able to find any studs out there to put in the used case.

    I've also heard that some two stroke cases were essentially press fit together so when the time comes to split the cases, I may have to sprinkle some fairy dust on it to break them apart.

    John

  6. #6

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    Good news!
    Thanks to your help, I had good success this afternoon. I gently added heat to the aluminum cases surrounding the studs (ala MAPP Gas torch) and slowly unscrewed the three remaining head bolt studs. It was touch and go, but it worked. Now with my confidence up, I can remove the studs from the case that's on the engine and insert them into the replacement case.
    At my glacial pace, I might have this thing running for next year's season.
    Not the prettiest crankcase on the donor engine....
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