Bolt

[simpletool]

Bugger, something else to worry about. Have all the bits and was going to do this belt change myself with original bolt......hmmmmmm.

[The Dan]

If you are going to do your timing belt, then make sure you replace the idler bolt. It has not really got anything to do with power levels. It only has to do with the bolt already having cracks. If in doubt, take your old bolt to an engineer for a crack test or xray and you will find it is fubar.

We are using 10.9 grade bolts as 12.9 is usually a cap head and I have seen these foul on the lower cover as they sit too proud.

A breakage of a new geniune bolt is not a common thing so don't everyone start getting paranoid, out of the approx 80 timing belts I have done on skylines, this is the only new one to have broken. This is why I am taking on the experiment because we have the resources at our disposal and it will also help to clarify some cryotreating questions we have at the same time.

Hopefully it goes in for treatment this weekend. We are waiting in them having enough other jobs to warrant such a small one. We have also found that no bolt manufacturers will give any gaurantee on a bolt for any reason, so if a new one breaks, you are on your own.

[83CKS]

Oh No's..

*Fingers Crossed* Mine's all good....

Edited October 21, 2009 by 83CKS

[Wacky Dee]

I'm so scared now I might just pull out both the idler and tensioner bolts and run without them

[ezy_09s]

Does anyone know the bolt dimesions to see if this could be cross referenced to any arp stuff..like an L19 bolt (260,000 psi tensile strength which is 1792 Mpa).

Overkill yes..but for peace of mind i wouldnt mind the extra few $$.

[Psymon]

I was wondering this myself when i was looking at my broken stud last night!

[Swiper the Fox]

we looked at upgrading to a better/harder material bolt but were a little worried the stronger bolt without any sort of flex may actually cause the cast iron block to fatigue and possibly crack the casting.

new genuine bolts and studs are the go in my opinion.

[dazmo]

I agree with Paul. I have done many timeing belts on GTR's of all power levels useing new factory bolts and have never had a problem. I would say that the bolt breaking in this case is just pure bad luck. And as Dan stated this is not a common problem so lets not all get paranoid.

we looked at upgrading to a better/harder material bolt but were a little worried the stronger bolt without any sort of flex may actually cause the cast iron block to fatigue and possibly crack the casting.

new genuine bolts and studs are the go in my opinion.

[simpletool]

If you are going to do your timing belt, then make sure you replace the idler bolt. It has not really got anything to do with power levels. It only has to do with the bolt already having cracks. If in doubt, take your old bolt to an engineer for a crack test or xray and you will find it is fubar.

We are using 10.9 grade bolts as 12.9 is usually a cap head and I have seen these foul on the lower cover as they sit too proud.

A breakage of a new geniune bolt is not a common thing so don't everyone start getting paranoid, out of the approx 80 timing belts I have done on skylines, this is the only new one to have broken. This is why I am taking on the experiment because we have the resources at our disposal and it will also help to clarify some cryotreating questions we have at the same time.

Hopefully it goes in for treatment this weekend. We are waiting in them having enough other jobs to warrant such a small one. We have also found that no bolt manufacturers will give any gaurantee on a bolt for any reason, so if a new one breaks, you are on your own.

How are the grade 10.9 bolts going? You haven't found them coming loose at that tension? or do you put some loctite on them?

Also so I can source the bolt before disassembly, is the M10 bolt a 1.5mm pitch?

[R33S2]

this is the only new one to have broken

Come on Dan I know of another one that caused a great deal of shite because I bought a turbo off the guy and because I am a friend he dicked me around no end. If I remember rightly an investigation was carried out and the bolt was found to be faulty.

A button head cap bolt is lower profile than a normal bolt and wont fowl.

[The Dan]

Come on Dan I know of another one that caused a great deal of shite because I bought a turbo off the guy and because I am a friend he dicked me around no end. If I remember rightly an investigation was carried out and the bolt was found to be faulty.

A button head cap bolt is lower profile than a normal bolt and wont fowl.

Not sure what that means Terry but no, it was not a new bolt.

I was instructed by that customer to not replace the bearings...only the belt. The idler bolt was never touched and broke 3000km later. That was a factory bolt and yes it was tested and found to have multiple fractures throughout.

I have all of these grade 8.8 bolts here ready to send off for MPI, just waiting for the oportunity.

[The Dan]

How are the grade 10.9 bolts going? You haven't found them coming loose at that tension? or do you put some loctite on them?

Also so I can source the bolt before disassembly, is the M10 bolt a 1.5mm pitch?

You need an M10 x 1.5 x 70mm bolt.

As stated above, no problems with the grade 10 bolts being used. Cap heads sit proud and can touch the timing cover so stay away from the grade 12 bolts if you can. There is no need to go that high anyway.

Make sure the washer goes back under them

[T04GTR]

silly question, but have they been tensioned with a torque wrench? not with the first click of the elbow?