Head bolt torque?

Desertrat · Post by **Desertrat** » Sat Apr 14, 2007 11:23 am

I have been looking for the head bolt torque in a few different manuals I have downloaded but they are all different! What does the real manual say?

Vlade · Post by **Vlade** » Sat Apr 14, 2007 12:48 pm

I'll tell you how I do it and I have never had a problem that related to this.

Wet torque at 103nm

Ummm most gasket sets will have some instructions with them if they don't... Do a 30nm all round first, then do the 103nm... and remember to keep the sequence!

Desertrat · Post by **Desertrat** » Sat Apr 14, 2007 3:23 pm

thanks, this is what i thought but i broke a bolt hence me asking. maybe my torque wrench is not calibrated right?

The Calibrator · Post by **The Calibrator** » Sat Apr 14, 2007 6:40 pm

100nm on a headbolt is crazy.

Phinx · Post by **Phinx** » Sat Apr 14, 2007 7:28 pm

agreed 103 nm ...

When I did mine I used those settings

veecee · Post by **veecee** » Sun Apr 15, 2007 8:57 am

The Calibrator wrote:100nm on a headbolt is crazy.

you crazy esse', dont you know they loco!!!

but seriously, do you mean its too much or too little? what do you recommend?

The Calibrator · Post by **The Calibrator** » Sun Apr 15, 2007 9:09 am

The 1st question is arfe they stretch bolts? If not then around 85nm is the norm. Check in your FSM
If they are stretch bolts then they HAVE to be angle torqued to get accurate results.They should also be replaced each time.
You may get away with huge torque on a stretch bolt for a while but it will come back and bite you in the ass at some point.

Remember in the old days how you had to retorque the head bolts after a 1000km? Thats because the head gasket settles to overcome that and to get more consistent clamping stretch bolts were developed.a large portion of the tightening torque goes into overcoming friction so now you ignore torque.
The bolt is tightened to the plastic deformation stage ie: just before they snap this then allows the bolt to compensate as the gasket settles and you are not measuring friction and hoping it actually clamping the gasket.

This is why serious engines use studs much less friction to overcome so more accurate clamping torque.

veecee · Post by **veecee** » Sun Apr 15, 2007 5:51 pm

The Calibrator wrote:The 1st question is arfe they stretch bolts? If not then around 85nm is the norm. Check in your FSM
If they are stretch bolts then they HAVE to be angle torqued to get accurate results.They should also be replaced each time.
You may get away with huge torque on a stretch bolt for a while but it will come back and bite you in the ass at some point.

Remember in the old days how you had to retorque the head bolts after a 1000km? Thats because the head gasket settles to overcome that and to get more consistent clamping stretch bolts were developed.a large portion of the tightening torque goes into overcoming friction so now you ignore torque.
The bolt is tightened to the plastic deformation stage ie: just before they snap this then allows the bolt to compensate as the gasket settles and you are not measuring friction and hoping it actually clamping the gasket.

This is why serious engines use studs much less friction to overcome so more accurate clamping torque.

the ca18det's dont have stretch bolts. but i go with trust on this one, cos that is what my engineer told me! so mine were re-used. the FSM also states the procedure for removing and installing headbolts, and 103Nm's is the final torgue figure. you have to torque to 30Nm's first, then remove, then to 103Nm.

and this reminds that my engineer also told me to retorque them after run-in. i cant remember if i did or not. maybe thats why my engine is lethargic, or maybe my butt-dyno is worse than phinx's. lol - its probably that!

Phinx · Post by **Phinx** » Mon Apr 16, 2007 6:36 am

Hay Hay....

I need my Butt Set-in ....

Maybe I should recheck my head-bolts because Im down on power....

Vlade · Post by **Vlade** » Mon Apr 16, 2007 7:16 am

Been doing 103nm all my life never had problems... Most of them are still the same bolts... and nope they not stretch bolts...

Draco · Post by **Draco** » Mon Apr 16, 2007 9:04 am

i think I am a lucky oak, about almost a year ago I thaught I had blown a head gasket, with some advice from a friend I went to someone to retorque the head, the guy torqued the head at 110 nm, never had a problem since then.....luckely the bolts didn't break....

Desertrat · Post by **Desertrat** » Mon Apr 16, 2007 5:29 pm

yea your lucky, i re used myn and it broke just under a 100

The Calibrator · Post by **The Calibrator** » Mon Apr 16, 2007 8:08 pm

I will do some research and give u a definite answer.