M102 head tension

[vk6fun]

Hi from Western Austrralia!

Thanks to the help I have received so far from this forum, I am now ready to undo the head bolts on my son's engine.

They are of the "star" type, like allen screws. I have obtained trhe appropriate bit and a torque wrench and ready to undo...

It occured to me that I should note the tension on these as I undo them to make sure they were done up correctly in the first place.

Can anyone tell me what this tension should be?

cheers from VK6FUN (Peter)

[t walgamuth]

i wouldn't worry about that.

some of the head bolts are reusable and need to be measured to determine if they are stretched beyond the usable limit or not.

going back on is what you want to worry about.

unless you have some reason to worry about them. do you have some clue that they may be on too tight?

tom w

[Ron in SC]

I think the gasket kit comes with a paper that instruts as to tension procedure. Three stages, first with torque wrench, then 90 degrees and then 90 degrees again. Done in a specific pattern.

I don't think you can check the tenison of the installed bolts and I don't think checking would be useful.

[vk6fun]

yes you are right.
we just wanted to see if they were put on right.
can you tell us the correct tension, when we put it back on?

cheers from Peter vk6fun

[Ron in SC]

Tightening Torque
Note: Oil the thread of bolts and the contact service of the bolt head and insert. See diagram

Stage 1 70 Nm
Stage 2 90 Degree Angle Of Rotation
Stage 3 90 Degree Angle Of Rotation

Cylinder Head Bolt Stretch
Note: If cylinder head bolts exceed the specified length (L) they should be scrapped and replaced by new bolts.
Scrape if exceed 108.4 mm See diagram


During engine repairs that include removal of cylinder head bolts, special care and precautions must be taken during reassembly.
Upon removal of a cylinder head bolt, it is possible for engine oil or coolant to flow into the bolt hole, filling the area of the bolt threads.
During reinstallation and tightening of the cylinder head bolt, this oil or coolant would be highly compressed by the threaded end. It is possible that the resulting pressure of the liquids in the bolt hole could cause the engine block to crack.
Prior to the installation of a cylinder head bolt, all fluids and dirt must be removed from the bolt hole by means of compressed air (be sure to observe safety precautions and wear eye protection).
Never use any kind of impact wrench for the removal and installation of cylinder head bolts.
Hand tools only must be used for the removal and installation of cylinder head bolts. Ensure that bolts are turned slowly until they are hand tight, and then torqued down according to specifications. Always adhere to the tightening torque and tightening sequence indicated in applicable service literature.

Peter,

Have you ever torqued heads in place with stretch type bolts such as these?

If not, you will hesitate when you start because you will think that you are going to break the bolt. Also, either mark their position after the torque wrench step with paint so that you don't lose track of which ones you have stretched to the next step, OR make sure that there are no interruptions that will make you lose your place in the sequence.

Also, get ready for a workout. Unless your last name is Schwarzenegar, you will be huffing and puffing when you're done.

Best of luck and keep us posted on progress.

Have a great day,