Question on torque values (Engine rebuild)

[pjo046]

I have just started to assemble my engine now, after getting the head rebuilt, the block lapped and the crankshaft, pistons, rods, flywheel and clutch balanced at an engine builder.

I am a bit unsure about the torque values given in the workshop manual. First of all, are the bolt threads supposed to be oiled, or installed dry with the given values? I see that the manual states that the head studs should be lightly oiled, as should the balance shaft cover bolts. So all other values are for dry fastening?

Furthermore, what does it mean when it says for example 30 + 3 NM as torque value?` If there are several steps, it says so in the manual. So what are the values where there is only one step, but two values like above?

I just installed the lower balance shaft cover tonight. I carefully cleaned all bolt holes with a tap, and also cleaned the threads on the bolts. I oiled them before installation, and followed the tightening instructions in the manual. Still, I managed to strip one of the small M6 bolts. It felt like 10NM was far too much torque, and I afterwards thought it had been better to install the bolts dry. The torque wrench was bought new today, as I only had a 20-210NM wrench from before. So I am pretty sure the wrench is not the problem. It is rated at 2-24NM, so the 10NM was in the middle of it's range as well. Could too much oil on the bolts have been the problem?

I see that the early 944 engines have the M6 bolts rated at 8NM whereas the 87 and onwards (+ the 86 951 which my engine is) are rated at 10NM..

The bolt that got stripped is number ten in the below picture.


When I say stripped I mean it spun, i.e. the resistance stopped getting higher when I kept turning the wrench without things getting fastened enough for the wrench to engage. So it isn't completely stripped, but the threads surely has started deforming. I just left the bolt in it's place as I assume it is doing some purpose as opposed to not be there. Am I screwed, or can I just leave it be and assume things will be fine? The loctite 574 got squesed out evenly all the way around, and that should be a good sign I guess.

[flash75]

If it doesn't leak it should be ok to leave it as is. It's not structural.

Clifton

[pjo046]

That's good! :-)
Did the other balance shaft today, but this time I installed the small bolts dry. I also first tightened them in the correct order till 6Nm, then 8Nm and finally 10Nm. One of the bolts took much more turning on the last round then the others, so I just stopped. It is tightened to 8Nm and then some. Figured that was better than to risk another spun bolt.

Does anyone know the meaning of the 30 + 3 etc torque values in the manual?