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5 GT Turbo Oversize head bolt number 10 to M12, possible?

itzik

Member
Hi all,

The thread for Bolt number 10 is damaged, I tried helicoil with no luck, can I go oversize to M12? Problem is i need to drill the cylinder head also to allow the bolt to pass through the head... I saw a small water pass underneath, need advise here...

Thank you

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When I had a car in with a failed head bolt thread, I dropped the sump off, took the opposing main bearing bolt out and put a stud all the way through top to bottom. It was either that or new block, and the owner asked me to try the stud first. It lasted until the car was written off in a crash 2 owners and 5 years after. This was on a 21 so get a C-series block checked and see if you can pass a stud all the way through the block to the main bearing cap..
 
When I had a car in with a failed head bolt thread, I dropped the sump off, took the opposing main bearing bolt out and put a stud all the way through top to bottom. It was either that or new block, and the owner asked me to try the stud first. It lasted until the car was written off in a crash 2 owners and 5 years after. This was on a 21 so get a C-series block checked and see if you can pass a stud all the way through the block to the main bearing cap..

I am afraid on the C engine the threads are blocked, they have a bottom...

I am trying to get an m12-m10 stud reducer, and use a nut instead of a bolt.
 
You should be able to use a "M10 x1.5 Thread repair kit". Fairly easy to do. Just make sure you keep the drill perpendicular to the block face. Get a friend to to check that you're lined up.
 
This may be another option rather than helicoil. These are solid bushing inserts.

 
This may be another option rather than helicoil. These are solid bushing inserts.


Either or. they both achieve the same thing. What you put up should be stronger.
 
It seems that the previous owner who helicoiled this thread drilled a bigger hole then he should... that's why the helicoil is failing when I am trying to torque it down to 65nm, I saw a "Big sert" kit for this sort of situation but the kit cost around 450USD...
 
have you ran a plug tap to the bottom of the hole?
NO I haven't, the helicoil attempt goes deep, I hope there is something left on the bottom.

Anyway I found in Amazon a basic "Big sert" kit for around $100 and a special m10 insert 2.5cm long... I will give it a try, this kit is for an m14 tap and the inside diameter is an m10x1.5... will give it a try as helicoil won't help here anymore.
 
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Can you drill and tap it to M12 or have you Got to go bigger ? I had a M12 all thread bolt (70mm long) with a 6mm hole drill up the center on a lathe . Tap the block out to M12 locktite in to the block . Cut off flush with block . Now drill the insert in stages out to take A M10 tap , job done you have made your own insert ,
 
Can you drill and tap it to M12 or have you Got to go bigger ? I had a M12 all thread bolt (70mm long) with a 6mm hole drill up the center on a lathe . Tap the block out to M12 locktite in to the block . Cut off flush with block . Now drill the insert in stages out to take A M10 tap , job done you have made your own insert ,
That is a great idea, In my case I need an M14 bolt as the hole is too big for M12 now (more then 11mm)... I have an M14 steel bolt to use...
 
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