head bolt problem

[cardiffboy27]

hey all what a week it has been!

after a blown waterpump and headgasket i have a problem woth one of the head bolts,
is seems as the thread on the block has gone the bolt tightens and then just slips again and again
does anyone have any idea how this can be sorted and if so what kinda price i should pay ?
many thanks in advance
Ian

 

[SammoHung]

I'm not sure if this is possible on a block...but:

...normally if a thread pulls out; then you can have the thread re-tapped (re-cut) to a larger size.....then a 'helicoil-insert' can be fitted that binds nicely to the new larger thread, but it has its own internal thread that is equal to the original size thread of your bolt.

something like this..
http://www.boltman.com/images/custom/nHelicoil1x11_8Nitronic60.jpg


Coils are cheap as chips but it's the same old story with how long it will take somone to dothis for you (labour charge per hour or part thereof!!)..

Labour can typicaly rance from £20 to £45 quid per hour dependingif its your local salt of the earth mechanic or some monney grabbin main dealer!!

Good luck mate

 

[AMY]

I wouldn't recommend helicoil for a head bolt it has too much stress on it, I have known people do this only to have problems with the head gasket sealing around that bolt. First off I would check that all the bolts are in the correct place, as if I remember correctly some are longer than others. If you are using a short bolt in place of a long it won't grip properly. Secondly pull the head bolt out and check if the thread is ok on it as you may be lucky enough to have just damaged the thread on the bolt and not the head. Is the bolt tightening right down before it slips?

 

[Fordy]

short bolts at the back (inlet side) and long ones at the front (exhaust side) iirc

 

[RaptorRVL]

Hmm, I did some helicoils on my engine when putting the head back again.
I got some coils and the set to do it myself from a company nearby who work with ship engines and stuff. Told me it would hold just well and so far it did

Then again I have no idea if there are different types of helicoils (I assume there are) and what stuff I got. Also couldn't be bothere much about it back then, cause when it didn't hold I still had/have a spare 1.2 engine I could put in. So I figured it would be a nice test of sorts

 

[cardiffboy27]

yeah the bolt is going right down before it slips and the bolt its self is A OK!

also when the head came off im certan that the long bolts were inlet side and shorter ones on the exhaust

 

[AMY]

I guess you try a helicoil then, as some people have had results with them. Personally I would either just pick up another engine as they are so cheap, or try to get the hole re tapped to accept slightly larger bolt.

 

[Andrew]

Helicoils if done properly will be stronger than a plain thread. If there is something we need to open up more than a couple of times a year, we helicoil them to prevent future problems, especially into ally.

Nice little trick I worked out when I was doing the head on a Primera - the last person to do it had mashed up nearly all the threads in the block - it was possible to get the bolt started, but it was difficult and there was no way the torque reading would have had anything to do with preload. Getting a tap to clean them up would have cost a lot and taken time, so I ground two groves down the side of one of the old bolts, turning it into a cheap tap. They are fairly hard anyway, so didn't need any heat treating or anything. Worked a treat.