Head bolt torque?

[nokivasara]

Will the torque applied to TTY head bolts change much if the job is done in cold temperature?

They should be torqued to 60NM, +90, +90 degrees on a cold engine. This is probably at ISA?
Lets say I use the above torque on a engine that is 10C or 0C instead, would the difference due to thermal expansion of the head and bolts be enough to cause trouble?

[Zynerji]

I doubt torque to yield bolts would be effected by such a small temperature window.

I may be wrong, however...

[nokivasara]

I doubt torque to yield bolts would be effected by such a small temperature window.

I may be wrong, however...

Well, this is exactly my take on it, that's why I asked

[Big Tea]

If all metals are at the same temperature, would it matter? Ally will expand more than steel but should still be well within the tolerance of torque. I was going t post the expansion table, but it is so minuscule compared to hot engine/cold engine it is not worth posting.

[Tommy Cookers]

bolts yield will start at around 3000 ppm of (elastic) strain

the relative linear thermal expansion of Al alloy to steel is about 10 ppm/deg C

[nokivasara]

Thanks! I thought that it would be ok but it would suck to end up with a snapped bolt or leaking head gasket just because the temps were too low.
Now I can fix it first thing in the morning, need to fix the heater in the garage too...

[godlameroso]

Honda?

[63l8qrrfy6]

Will the torque applied to TTY head bolts change much if the job is done in cold temperature?

They should be torqued to 60NM, +90, +90 degrees on a cold engine. This is probably at ISA?
Lets say I use the above torque on a engine that is 10C or 0C instead, would the difference due to thermal expansion of the head and bolts be enough to cause trouble?

No reason to worry, torque to yield bolts are designed such that the stress-strain curve is flat in the operating region which means that once they have yielded the pre-tension is highly insensitive to variations in torque, angle and other factors including temperature.

With a standard bolt the pre-tension variaton is in the range of +/-15% with a torque+angle tightening method. The effect of ambient temperature is nothing in comparison to that.

[nokivasara]

Honda?

Skoda PD TDI

My username is finnish for diesel. Or soothammer to be precise but it means diesel.

Will the torque applied to TTY head bolts change much if the job is done in cold temperature?

They should be torqued to 60NM, +90, +90 degrees on a cold engine. This is probably at ISA?
Lets say I use the above torque on a engine that is 10C or 0C instead, would the difference due to thermal expansion of the head and bolts be enough to cause trouble?

No reason to worry, torque to yield bolts are designed such that the stress-strain curve is flat in the operating region which means that once they have yielded the pre-tension is highly insensitive to variations in torque, angle and other factors including temperature.

With a standard bolt the pre-tension variaton is in the range of +/-15% with a torque+angle tightening method. The effect of ambient temperature is nothing in comparison to that.

+/-15% is quite a lot. Is there a short answer to why the torque+angle is a better way to reach the desired clamping force? I mean if I use the torque+angle method and watch what the final torque is, why shouldn't I be able to just set the torque wrench to that number for the last sequence when tightening?

[hUirEYExbN]

Honda?

Skoda PD TDI

My username is finnish for diesel. Or soothammer to be precise but it means diesel.

Will the torque applied to TTY head bolts change much if the job is done in cold temperature?

They should be torqued to 60NM, +90, +90 degrees on a cold engine. This is probably at ISA?
Lets say I use the above torque on a engine that is 10C or 0C instead, would the difference due to thermal expansion of the head and bolts be enough to cause trouble?

No reason to worry, torque to yield bolts are designed such that the stress-strain curve is flat in the operating region which means that once they have yielded the pre-tension is highly insensitive to variations in torque, angle and other factors including temperature.

With a standard bolt the pre-tension variaton is in the range of +/-15% with a torque+angle tightening method. The effect of ambient temperature is nothing in comparison to that.

+/-15% is quite a lot. Is there a short answer to why the torque+angle is a better way to reach the desired clamping force? I mean if I use the torque+angle method and watch what the final torque is, why shouldn't I be able to just set the torque wrench to that number for the last sequence when tightening?

Torque is a really unreliable way of prestressing a bolt. So generally, critical bolts are tightened until they are just starting to take on a load and then a known quantity of load is applied using angle.

https://www.norbar.com/News-Events/Blog ... -Explained

[godlameroso]

Honda?

Skoda PD TDI

My username is finnish for diesel. Or soothammer to be precise but it means diesel.

Will the torque applied to TTY head bolts change much if the job is done in cold temperature?

They should be torqued to 60NM, +90, +90 degrees on a cold engine. This is probably at ISA?
Lets say I use the above torque on a engine that is 10C or 0C instead, would the difference due to thermal expansion of the head and bolts be enough to cause trouble?

No reason to worry, torque to yield bolts are designed such that the stress-strain curve is flat in the operating region which means that once they have yielded the pre-tension is highly insensitive to variations in torque, angle and other factors including temperature.

With a standard bolt the pre-tension variaton is in the range of +/-15% with a torque+angle tightening method. The effect of ambient temperature is nothing in comparison to that.

+/-15% is quite a lot. Is there a short answer to why the torque+angle is a better way to reach the desired clamping force? I mean if I use the torque+angle method and watch what the final torque is, why shouldn't I be able to just set the torque wrench to that number for the last sequence when tightening?

Tightening torque corresponds to, but does not equal bolt tension. There are several factors that can affect torque corresponding to bolt tension(stretching the bolt is one of those reasons). The bolt tension on head bolts come from them stretching a certain amount. Some head bolts can be reused if not stretched beyond a certain point.

In the service manual for reused head bolts on Hondas that measure out fine, you do 60nm + 90° + 90° but do an extra 90° if the headbolt is new.

Normally you don't stretch bolts, the tightening torque corresponds to a level of tension that won't stretch them. You can put 105nm on a 12mm thread grade 10 bolt without fear of stretching it, or 300nm on an axle nut without worrying if you're going to snap the axle stud.

Headbolts are meant to stretch.

[63l8qrrfy6]

Honda?

Skoda PD TDI

My username is finnish for diesel. Or soothammer to be precise but it means diesel.

Will the torque applied to TTY head bolts change much if the job is done in cold temperature?

They should be torqued to 60NM, +90, +90 degrees on a cold engine. This is probably at ISA?
Lets say I use the above torque on a engine that is 10C or 0C instead, would the difference due to thermal expansion of the head and bolts be enough to cause trouble?

No reason to worry, torque to yield bolts are designed such that the stress-strain curve is flat in the operating region which means that once they have yielded the pre-tension is highly insensitive to variations in torque, angle and other factors including temperature.

With a standard bolt the pre-tension variaton is in the range of +/-15% with a torque+angle tightening method. The effect of ambient temperature is nothing in comparison to that.

+/-15% is quite a lot. Is there a short answer to why the torque+angle is a better way to reach the desired clamping force? I mean if I use the torque+angle method and watch what the final torque is, why shouldn't I be able to just set the torque wrench to that number for the last sequence when tightening?

Shortest answer I can come up with:
With torque only, an unknown portion of the torque goes into overcoming the bolt head and thread friction. Torque only is the least reliable method of doing up a joint except of course doing it up "by feel".

When using an angle method you directly control the joint displacement (for each full turn of the nut the joint displacement is equal to one thread pitch) so this process is largely insensitive to friction. However you still have to apply the first settling torque which of course will cause the initial tension to vary with friction.

The most accurate way to do up a joint is to directly control the stud elongation by either hydraulic tensioning, ultrasonic or strain gauge measurement or directly measuring the stud elongation if possible (non-blind threaded holes such as the ones on many connecting rods).