Jump to content
SAU Community

Recommended Posts

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.

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-4893722
Share on other sites

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 $$.

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-4894381
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-4894667
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-4894826
Share on other sites

  • 3 months later...
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?

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-5091635
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-5098189
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-5099304
Share on other sites

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

Link to comment
https://www.sau.com.au/forums/topic/290065-bolt/page/2/#findComment-5099614
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Not sure the US can import anything other than the C34 Stagea's, but if you can and you need to to tow, DO NOT under any circumstances get an M35 Stagea. If it is just as a family car and your country/state allows it, absolutely and definitely get an M35 (3.5L if possible as it is effectively a 350Z) over a C34.
    • Punch your VIN (nm35-xxxxxx) into Amayama.com You can see everything there quite easily.
    • Thanks for that, I'll check it all out. I can always do the brakes last anyway if its a problem.  The 16's are super cool, if they do fit I'll cruise around with them for a bit.  
    • Well, that's kinda the point. The calipers might interfere with the inside of the barrels 16" rims are only about 14" inside the barrels, which is ~350mm, and 334mm rotors only leave about 8mm outboard for the caliper before you get to 350, And.... that;s not gunna be enough. If the rims have a larger ID than that, you might sneak it in. I'd be putting a measuring stick inside the wheel and eyeballing the extra required for the caliper outboard of the rotor before committing to bolting it all on.
    • OK, so again it has been a bit of a break but it was around researching what had been done since I didn't have access to Neil's records and not everything is obvious without pulling stuff apart. Happily the guy who assembled the engine had kept reasonable records, so we now know the final spec is: Bottom end: Standard block and crank Ross 86.5mm forgies, 9:1 compression Spool forged rods Standard main bolts Oil pump Spool billet gears in standard housing Aeroflow extended and baffled sump Head Freshly rebuilt standard head with new 80lb valve springs Mild porting/port match Head oil feed restrictor VCT disabled Tighe 805C reground cams (255 duration, 8.93 lift)  Adjustable cam gears on inlet/exhaust Standard head bolts, gasket not confirmed but assumed MLS External 555cc Nismo injectors Z32 AFM Bosch 023 Intank fuel pump Garret 2871 (factory housings and manifold) Hypertune FFP plenum with standard throttle   Time to book in a trip to Unigroup
×
×
  • Create New...