Hey All,


Putting a new head gasket on and did the 55Nm, then the next 90deg before I realized that I had to take it off. I fixed the impossible to reach exhaust nuts/bolts and put the head back on.



Have done the 55Nm and 1st 90deg again with a couple hours in between. Left if for a couple of days to get the 12 pt. Torx and am ready for the last 90 deg. My worry is that the gasket is a crush gasket and that I have already crushed and am now out of spec for another 90 deg turn? Or is it the bolts that stretch over time to allow the two 90 deg turns? The bolts are going to need a long breaker bar to get them to move anymore and I am freaked about over torquing and possibly breaking a bolt. Please help and DO NOT tell me that I have to get another head gasket :-)


Thanks!

Useful info here:
M103 head gasket re-torque - I tried it

I just went out and thought I would do the last 90deg with the torque wrench attached. Well, it was disappointing. Several were already well over 80lbs (90lbs is max from what I've read) so I didn't move them as much while several more never got there, even if I went a little past 90 deg.



I know there's a reason why they don't use a torque wrench, but it makes sense to at least check. I guess I'll run it for awhile and then spend an afternoon re-torquing one day? Or do it now? Kinda frustrated. At least the head bolts are easy to access. Thanks for your thoughts!

The gasket actually swells a smidge the first heat cycle and that's where most of its sealing ability comes from. You should be fine.

__________________

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Final torque is going to be higher than initial torque so any recheck reading you take isn't accurate unless you fully loosen the bolt and start over.

Starting friction is higher than running friction further clouding the readings. Also, if you tighten a bolt with a click type torque wrench, giving it another pull to hear a click does nothing beyond adding to torque wrench wear.

The goal of tightening bolts is to generate enough clamping force. Torque is an inference of clamping force. The problem with using torque in a critical application is thread and under head friction alters the torque needed to generate enough clamping force for a given torque reading.

Enter torque to yield bolts. These bolts are lightly torqued just to hold everything together then tightened until the bolt is stretched. ( think of the bolts as a large spring. ) The bolts are actually stretched to the point the metal yields and takes a permanent set. Once they bolts reach the yield point, they won't generate more clamping force no matter how much further you turn them.

You can feel the bolts yield as you are getting towards the last bit of rotation. The amount of rotation is speced to assure bolt yield is reached before you hit the final spec. Many times I'll do initial torque and first rotation then last rotation be feel.



Torque to yield bolts generally can be reused at least once and sometimes more than that. The factory , regardless of brand , generally recommends they be replaced after every use however, they are taking into account the show can't verify bolt usage and labor to clean / inspect bolts outweighs replacing them.




I'd retorque now. Completely loosen one at the center of head, then do a full torque sequence ( fully loose , initial torque , then rotation.) then continue through the pattern. Once this is complete, it will be just fine.