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Thread: Removing head bolt studs in aluminum case

  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
    Aug 2004
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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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  7. #7

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    Now for the bad news...
    I got a little cocky and figured I would practice my snapped-off stud removing skills. I had a brand new set of easy outs, drilled the proper size hole, tapped in the easy out, applied heat, and....dang it. snapped off the easy out.
    I think it was probably not enough heat. The first time I tried turning the easy out, I could feel it twisting very slightly. At that point, I should have applied more heat because the second time I tried it, the easy out snapped even with the deck. I don't think I'll ever get that one out. :<(
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  8. #8
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    Quote Originally Posted by swolf View Post
    Now for the bad news...
    I got a little cocky and figured I would practice my snapped-off stud removing skills. I had a brand new set of easy outs, drilled the proper size hole, tapped in the easy out, applied heat, and....dang it. snapped off the easy out.
    I think it was probably not enough heat. The first time I tried turning the easy out, I could feel it twisting very slightly. At that point, I should have applied more heat because the second time I tried it, the easy out snapped even with the deck. I don't think I'll ever get that one out. :<(
    Even in the best of situations it can be tricky trying to remove steel bolts from aluminum. Sometimes the only method is to end mill out the center of the bolt and then pick the remaining steel threads out with a small dental pick.

    Jerry

  9. #9
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    Nov 2018
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    Reno NV
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    I tried to remove two cylinder studs from a spare left case I have yesterday. One came out and one broke off. Used same system and heat on both, so it can be a crap shoot if they come out. Broken studs typically need to be milled out as per Jerry's post, as they are an interference fit, and very tight.
    I also removed the locating screws on a 29 left case that hold the left bearing case race. I have two out so far, one to go that has had the screw slot previously butchered. This one may have to be drilled out. If I do this, I will need to make a new screw as I don't think they are available anywhere.
    Good luck.

  10. #10

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    Jerry and Mick,
    Thanks for your comments and insights. I'm glad this is a spare case that I hope I never have to use. In all my years of wrenching, and about a dozen attempts, I've only been able to remove one broken off bolt with an EZ. I saw two recommendations for EZ outs: One is a hollow diamond cutter bit and the other is a traditional EZ out, but the there are many more flutes and they are finer than the ones I'm used to seeing. The hollow diamond cutter was for drilling out a broken EZ out or broken tap. The fluted EZ outs was supposed to be tougher. Any comments on these two?
    John
    Diamond Tool Drill Bit b.jpgEZ Outs b.jpg

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