Head stud suspicious thread
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Topic author - Posts: 68
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#1 Head stud suspicious thread
Hi everyone,
I recently re torqued my cylinder head to find that one of the studs (the LH second row from front) wouldn’t torque up and now suspect the thread in the block is the issue. Interestingly I can undo and redo the the head stud and the thread draws it in and out but it won’t tighten up properly.
I found a small leak of water coming from the top of it when tightened, not good.
The stud is the one that is the unique size and slightly different shape, I’m wondering if anyone knows of this stopping it being withdrawn from the head? It certainly didn’t just pull out, but it is loose!
I’d like to inspect the head stud threads before deciding what to do next...
Cheers, Robert
I recently re torqued my cylinder head to find that one of the studs (the LH second row from front) wouldn’t torque up and now suspect the thread in the block is the issue. Interestingly I can undo and redo the the head stud and the thread draws it in and out but it won’t tighten up properly.
I found a small leak of water coming from the top of it when tightened, not good.
The stud is the one that is the unique size and slightly different shape, I’m wondering if anyone knows of this stopping it being withdrawn from the head? It certainly didn’t just pull out, but it is loose!
I’d like to inspect the head stud threads before deciding what to do next...
Cheers, Robert
1966 Series 1 2+2 (LHD), Manual, AC
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#2 Re: Head stud suspicious thread
If it's the dowel stud then no I don't think it will pull through the head.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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Topic author - Posts: 68
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#3 Re: Head stud suspicious thread
Hi Andrew,
Dam - had my suspicions that would be the case. Pretty sure it is the dowel stud. Looks like it’s a head off job if I’m to stand a chance of repairing.
Robert
Dam - had my suspicions that would be the case. Pretty sure it is the dowel stud. Looks like it’s a head off job if I’m to stand a chance of repairing.
Robert
1966 Series 1 2+2 (LHD), Manual, AC
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#4 Re: Head stud suspicious thread
I think so. Fortunately your car should have a short stud block so helicoiling the thread in the block should be an easy process.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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Topic author - Posts: 68
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#5 Re: Head stud suspicious thread
Thanks Andrew. Coming to terms with the thought of dismantling everything is a bit painful. Trying to read up if it is indeed 100% the case that the dowel stud doesn’t pull through the head, would hate to dismantle then find it’s not the case - mind you even a new stud would probably not make any difference - if the block threads are knackered, they are knackered.
Robert
Robert
1966 Series 1 2+2 (LHD), Manual, AC
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#6 Re: Head stud suspicious thread
It is 100% the case, unless someone has previously through-drilled the head to the size of the counterbore.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas
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Topic author - Posts: 68
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#7 Re: Head stud suspicious thread
Thanks seems right enough. I believe the cause of the issue was that the dome nut had basically got to the point where it was tight on and not turning anymore at which point it stopped and the stud started turning and so rather than clamping and torqueing up the stud just turned - results is probably a knackered thread in the block.
This morning I have removed the dome nut (by grinding off bit by bit until it broke free ) and re seated the stud as far down as it goes into to the block.
I then cleaned up the threads at the top of the stud and offered up a nut to see if I could get it to clamp and it seems to be OK but I have not fully torqued it yet. Will try with a replacement dome nut and if that fails then head off
Robert
This morning I have removed the dome nut (by grinding off bit by bit until it broke free ) and re seated the stud as far down as it goes into to the block.
I then cleaned up the threads at the top of the stud and offered up a nut to see if I could get it to clamp and it seems to be OK but I have not fully torqued it yet. Will try with a replacement dome nut and if that fails then head off
Robert
1966 Series 1 2+2 (LHD), Manual, AC
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#8 Re: Head stud suspicious thread
You probably already know this, but be sure when you try to torque the new dome nut that the top of the stud is not bottoming out inside the nut before the nut makes contact with the washer on the stud. I.e., there is room inside the dome nut between it and the top of the stud. Otherwise, you're just torquing the nut onto the stud, but not applying any force against the head.
Mark
67 OTS 1E14988, 2015 Camry XSE
67 OTS 1E14988, 2015 Camry XSE
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#9 Re: Head stud suspicious thread
Hi Mark, I think I’ve learned that lesson the hard way on this one particular stud, rather annoying
1966 Series 1 2+2 (LHD), Manual, AC
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#10 Re: Head stud suspicious thread
Head is off as thread is knackered - anyone got any tips on helicoil process?
1966 Series 1 2+2 (LHD), Manual, AC
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#11 Re: Head stud suspicious thread
It's pretty easy as a general principle.
In the kit you get a drill, an oversized tap and the coil with an inserter tool that breaks the coil tab off once it's seated. You drill the old thread out, tap with the supplied tap and then screw the coil in.
I've only ever done smaller (3/16" to 5/16" non critical) repairs myself as we get anything larger done by he engine machinist we use. You obviously need to be absolutely sure that the hole you drill is perpendicular to the head face.
If you've got one buggered thread you might have more so worth checking them too while you're there.
In the kit you get a drill, an oversized tap and the coil with an inserter tool that breaks the coil tab off once it's seated. You drill the old thread out, tap with the supplied tap and then screw the coil in.
I've only ever done smaller (3/16" to 5/16" non critical) repairs myself as we get anything larger done by he engine machinist we use. You obviously need to be absolutely sure that the hole you drill is perpendicular to the head face.
If you've got one buggered thread you might have more so worth checking them too while you're there.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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#12 Re: Head stud suspicious thread
Thanks Andrew i think il try and find a mobile specialist in the area because I’ve not got the gear to do a perfectly perpendicular repair and can’t risk it I don’t think. Seems to be a thing that people do
1966 Series 1 2+2 (LHD), Manual, AC
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#13 Re: Head stud suspicious thread
Good choice IMO.RobertGrieve wrote: ↑Sun Aug 19, 2018 3:35 pmThanks Andrew i think il try and find a mobile specialist in the area because I’ve not got the gear to do a perfectly perpendicular repair and can’t risk it I don’t think. Seems to be a thing that people do
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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Topic author - Posts: 68
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#14 Re: Head stud suspicious thread
All sorted, thanks for the advise, helicoil did the trick and did it myself with the help of a borrowed electro magnetic base drill, although probably overkill was perfect for the job.
Head now torqued up properly and no leaks at all. Took the opportunity to re shim the head whilst off also.
Robert
Head now torqued up properly and no leaks at all. Took the opportunity to re shim the head whilst off also.
Robert
1966 Series 1 2+2 (LHD), Manual, AC
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#15 Re: Head stud suspicious thread
Perfect. Shimming the head off the car is a lot easier and a good choice.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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