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trouble changing exhaust headers

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paulyzf600
Scooby Slapper



Joined: 24 Oct 2004
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PostPosted: 00:39 - 01 Aug 2005    Post subject: trouble changing exhaust headers Reply with quote
Due to holes and lots of rust on my down pipes I have decided I need to change them so I stripped them off today but whilst in the process I snapped a Stud leaving it stuck in the head (flush). I was super carefull taking great care on each stud and easing them out slowly but the last one just snapped so easily. Anyway now I have a problem I need the stud out obviously and I just don't like the sound of these stud extractors whats anyones experience with drilling and re-threading? to be honest I am half tempted to take the head off and get someone who has done it before to do it.

Anyone have any experience?
cheers
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 01:33 - 01 Aug 2005    Post subject: Reply with quote
What I said on the subject of drilling out sheared studs last time it came up:

Quote:
You would be best to drill a small pilot hole first, this needs to be ABSOLUTLEY bang in the middle of the bolt, then go up in drill sizes gradually taking it up and up. Often when you remove so-much metal from the middle of the bolt, it will collapse slightly and come out as you back-off the drill.

You eventually reach a critical size of hole where you need to stop and make a decision. This is the point where the hole reaches the same size as the depth of the screw thread (eg an M8 bolt you can go up to 6.5mm as the thread is 1.5mm deep on a standard pitch.).

Once you reach this point you can a) Re-tap the hole back to its original size, not ideal because you are probably going to leave bits of the old bolt in there but it is an easy option.

b) Overdrill the hole and fit a helicoil insert. This is best for an important structural fitting such as a cylinder head stud.


Both of these are usually possible without removing the head. You can do option a) and if it doesn't work go on to option b).

If you aren't happy you can drill a hole absolutley square in the middle of the stud, get someone else to do it.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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