Torque settings help required please

[Matt UK]

Morning all,

I'm replacing the gasket between the inlet manifold and the throttle bodies (it's sqeaking away due to sucking in air through a leak) so I've taken of the fuel rail, injectors etc to get at it.

I'm going to take the TBs off and clean up - key question is what sort of torque setting should I be thinking when putting back onto the manifold?

Any help would be much appreciated!

[Matt UK]

The bolts are M8 if that helps?

I'm thinking about 25 Nm unless i hear different?

[harry b]

No, 25Nm is for M8 in Carbon steel.
In aluminium maximum 16-19,5Nm depending on the quality of the aluminium.
With the use of helicoils you could go up to 22Nm.

Also recommend to use some anitseize like Loctite 8150.

[Matt UK]

Thanks fella!

[DVandrews]

harry b said:

No, 25Nm is for M8 in Carbon steel.
In aluminium maximum 16-19,5Nm depending on the quality of the aluminium.
With the use of helicoils you could go up to 22Nm.

Also recommend to use some anitseize like Loctite 8150.

The quoted torque for the manifold bolts is 25nm, as is the quoted torque for the M8 sump bolts which also go into aluminium, the longer M8 sump bolts are quoted at 30NM. 35NM is for M8 into Carbon steel.

Dave

[harry b]

If you use 10.9 and 12.9 bolts.
Not the standard type of bolts normally used in those places.

It is generally not advised to use higher grade bolts in aluminium.
The higher grades require much higher torques to get the amount of stretch in order to secure them from loosening. In a new thread it might hold a few times, but most certainly not in cast aluminium.
The threads will creap and deform, and you will never obtain these high torques.
I can't show copies of the DIN and ISO sheets of this due to copyrights, but also take a look here, all excerpts from the ISO and DIN.

http://www.yetmans.mb.ca/kohler/page3/page3.html
http://dodgeram.org/tech/specs/bolts/M_bolts.html
http://mdmetric.com/techindex.htm
http://www.downhillschrott.com/dhs/wissen/schraub_...