[Cloud9...68]

Another engine assembly question - in the section on tightening torque for the exhaust system nuts and bolts, the manual says to "coat all nut and bolt unions with Optimoly HT", which I gather is a copper-based anti-seize, of which I have a tube. Should this stuff be used on the studs that attach the exhaust manifold to the head? If so, it must mean the torque values listed in the manual are "wet" values, right?



Also, while on the subject of attaching the exhaust manifold (which I just got back from getting ceramic coated at Swain Tech), the torque specs in the manual are odd - they read:



M6: 8 + 2 Nm

M8: 20 + 2 Nm

M10: 40 + 5 Nm



What the heck does this mean? It sounds like the instruction is to torque the nut or bolt to the first value, and then follow it up with an additional twist of the second value, but does it seriously mean we're supposed to be able to discern as little as 2 Nm on the torque wrench? Or does it mean something different? Thanks.

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[flash]

cold and hot?

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[Cloud9...68]

[quote name='flash' timestamp='1335522695' post='126124']

cold and hot?

[/quote]

Possibly; hadn't thought of that. I wonder why they chose to write the instructions as they did, as opposed to:



M6: 8, 10 Nm

M8: 20, 22 Nm

M10: 40, 45 Nm



This seems more intuitive to me, but what the heck do I know...?

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[Lear35A]

Basically yes to your questions. The torque values are for after you have applied the anti seize. You go around and torque all the nuts at the lower value. Then you add 2 or 5 more Nm and go around again. It just evens things up. And they are all done cold.

BTW, in the engine bay a couple of nuts are very hard to reach with a torque wrench. (You may have to just estimate with a good old hand wrench.)

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[Cloud9...68]

Thanks, Lance.



With each passing day, I creep ever closer to finally being able to fire this thing up. The rate of progress can only be descibed as "glacial", though...

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[tamathumper]

Most torque wrenches aren't that accurate - some instructions say you should stop short by at least 5 ft. lbs. (not newton meters as you have above) and then tighten the rest of the way.



Maybe they're assuming much higher grade tools than we mere mortals would have.

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[Scott Collins]

Yah, the hard to reach ones are on the ends, especially the one nearest the front of the car. No soup for you my friend....

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[MB968]

[quote name='tamathumper' timestamp='1335574515' post='126148']

Most torque wrenches aren't that accurate - some instructions say you should stop short by at least 5 ft. lbs. (not newton meters as you have above) and then tighten the rest of the way.



Maybe they're assuming much higher grade tools than we mere mortals would have.

[/quote]



Yeah, I can't believe an engineer actually specified something like 20 Nm followed up with 22 Nm. Because of the difference between the static and dynamic coefficient of friction, I doubt that there was ANY expectation that the increase to 22 would even cause the nut to break loose if it was already at 20Nm. So, I have to assume that the intention is just to insure that all the nuts are in the same range of tightness. I'd equate this to the same as tightening the lug nuts or anything else where I always go around again with the torque wrench at the max setting in case tighetning the other nut/bolts seated the assembly better, and some of the first tightened are below the value desired.



And, don't forget that most of the torques specified are at their max., 75% of elastic limit. So, even with the +/- 5% range of most good torque wrenches, we should still be well below the point of yield.

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[Cloud9...68]

Sigh. Nothing on these cars is straightforward, it appears.

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[flash]

only the engine



ba dum bum

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[tamathumper]

"The point of yield" must be the polite way of saying "Just a little mo... @!#$"

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[MB968]

Not quite that bad. "Point of yeild" just means that the bolt will stretch and stay a bit stretched. It is not the point of failure which is typically a lot higher.

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