How important are torque settings on bolts?

Wig

myhooose wrote: »

My my industry (hydraulics) torque settings are for lubricated threads not dry ones so I assume it is the same for the motor industry. I read somewhere it can make quite a bit of difference.

If I remember correctly the order of tightening the cylinder head bolts is important too

It's an excellent point and will make a difference, but as there is no mention in the guides about oiling the bolts I always have put them in dry.

loofer

Wig wrote: »

If the torque wrench bought does not have an angle gauge he can either buy one seperate (draper do one) or he can do the angle by eye. I don't have an angle gauge but I still manage to do it by eye. I bought a draper gauge but was not very impressed.

The OP has his Haynes manual so the instructions are there for him, he will need a torque wrench capable of the highest torque setting. Angles after that can be done by eye.

Thanks peeps.

I wasn't suggesting I was going to do the job. Read it in the manual so thought I would ask the purpose. I knew it was there for a reason, just wanted to know the impact of not doing it.

The manual does give information on torque settings, stages and the order in which the bolts should be screwed down.

It also states that it should be tightened by 90degrees. Do I understand this to mean that you should tighten to the torque parameters and then a finally once more, turn it clockwise 90 degrees from that point?

alo6

loofer wrote: »

Thanks peeps.

I wasn't suggesting I was going to do the job. Read it in the manual so thought I would ask the purpose. I knew it was there for a reason, just wanted to know the impact of not doing it.

The manual does give information on torque settings, stages and the order in which the bolts should be screwed down.

It also states that it should be tightened by 90degrees. Do I understand this to mean that you should tighten to the torque parameters and then a finally once more, turn it clockwise 90 degrees from that point?

yep, thats correct. torque to spec then a final 90Degree turn.

For jobs like that new bolts should also be used, due to the stress and strain of being torqued for a second time.

Strider590

marlot wrote: »

Its vital, especially on a cylinder head which has to handle a lot of thermal stress.

Your correct, but OP stated "head cover" which really doesn't matter too much because there's almost no pressure behind it, due to the vented filler cap

moonrakerz

alo6 wrote: »

yep, thats correct. torque to spec then a final 90Degree turn.

I don't quite get the "90 degree" thing............

You torque down to the required figure or until the wrench "breaks" - you DO NOT torque it any further !

Gloomendoom

moonrakerz wrote: »

I don't quite get the "90 degree" thing............

You torque down to the required figure or until the wrench "breaks" - you DO NOT torque it any further !

Huh? If the specs say you torque it down and then add 90°, then that is what you do.

birkee

marlot wrote: »

Its vital, especially on a cylinder head which has to handle a lot of thermal stress.

The torque is set at a level enough to take the bolt into its elastic range, without going so far that it snaps.

Not to mention that too much, can distort the cylinder head, and that they need to be tightened in the right sequence, to avoid this distortion.

Lum

Didn't the OP say "Cylinder head cover", not "Cylinder head". I'm assuming he means what used to be called the rocker cover.

Not quite as important to get the torque right on those as you'll just get a bit of oil seeping, not a horrible engine failure.

Gloomendoom

Lum wrote: »

Didn't the OP say "Cylinder head cover", not "Cylinder head". I'm assuming he means what used to be called the rocker cover.

Not quite as important to get the torque right on those as you'll just get a bit of oil seeping, not a horrible engine failure.

Or a stripped thread... especially if the fastener is biting into aluminium.

Lum

Well yes, but you'd have to be completely incompetent to do that.