Head Bolt question

[frontman]

Just done the bolts on my new head and was wondering why it's 78 Nm + 90 +90 and not a spcific torque ? (as the earlier engines are 114 to 122).
I'm sure there must be a reason as I know quite a few different makes have various combinations, and have heard of some being tightend and then backed off.

[TonyN]

Cos thats how they are designed. They are stretch bolts, if you mess with them once you've tightened them up, you could ruin them.

Its why you never use them twice.

[DMAudio]

Angles are also usually more accurate than torque settings due to friction in the threads among other things. Toyota have always been good at revising their head tightening plans after they realise their original specs weren't up to scratch

[Albannach]

among other things.

What other things?

[DMAudio]

Hydraulic effect of any oils in the thread wells for one. I'm no engineer, but have been informed by engineers that differing metals, elasticity of bolts and factors of that nature make angled torqueing more effective.

[Albannach]

Hydraulic effect of any oils in the thread wells for one. I'm no engineer, but have been informed by engineers that differing metals, elasticity of bolts and factors of that nature make angled torqueing more effective.

How many engineers and which discipline? Next time you see one, ask them how angled torquing will compensate for dirty thread wells (dirty thread wells are an amateur's thing, a professional will never have problems of that nature).

[frontman]

head bolts

Cheers for that (did'nt mean to start a dispute) my only reason for asking was that when undoing the bolts some cracked like mad and some came undone without as much effort, so when I put the new ones in (after cleaning out the threads) I wound up the wrench untill one of the bolts was just on the limit of clicking, after checking roound the bolts some where tighter (clicked easily) and some would have gone some more. I know all is ok because I have followed all the proper procedures,

cheers for the response

Col

[Albannach]

If you remember which bolts cracked and which didn't, you'll see a pattern.

So long as the holes are clean and dry, there will be no issues.

[DMAudio]

How many engineers and which discipline? Next time you see one, ask them how angled torquing will compensate for dirty thread wells (dirty thread wells are an amateur's thing, a professional will never have problems of that nature).

It's OK, I'll bow to your clearly supreme knowledge of all matters, since you clearly are just looking to dispute everything I post. I promise I wont bother doing it again

[Albannach]

It's OK, I'll bow to your clearly supreme knowledge of all matters, since you clearly are just looking to dispute everything I post. I promise I wont bother doing it again

It's not personal. I have a go at everyone that comes on here and blethers secondhand nonsense. Just like folk have a go at me when I talk shite...

[frontman]

head bolts

Hey guys, nowt wrong with a bit of banter, keeps things interesting. And lets face it it's only about cars & trucks, not life or death !!!