yanmar 3110 head studs/nuts

[wethomas]

Because of an out of calibration torque wrench, I torqued the head bolts to 160 ft/lb instead of the factory spec of 130. During the install, none of the nuts binded or jumped, everything went smoothly. The out of calibration torque wrench was discovered when I broke a lug nut at 80 ft lbs the next day. I bought a new wrench and verified the head nuts at 160. This tractor is a complete rebuild. New gasket (copper coated) and a new head.

I am hesitant to loosen the bolts back to 130 now, given the fact that Ive already compressed the fire ring on the gasket. I don't believe that the valves will clash, All of my cylinder protrusions were perfect and there was no machining on the block deck and a new head.

Any opinions on this.

Thanks

[winston]

My fear would be stripping of threads. Way more costly than a new head gasket. I suppose if they were going to strip they probably already have. I have just filled the air with words and really don't want to recommend for you.

[wethomas]

Do you guys think I should back it off to 130

Or

Dis assemble and re assemble with new gasket


Im really not in the habit of messing around with diesel head gaskets, they have to be perfect, so I may have answered my own question.

Thanks

[Aaron]

I know those composite head gaskets need to be retorqued after running for a while because they compress (by design so that they fill any imperfections in the block & head surfaces- vs the factory metal gaskets that do not compress because the surfaces are brand new and perfectly flat & smooth) .

You MIGHT find that after a cycle of heating up and cooling down that the torque is close to correct or might even need more.
You also might find that the extra stress of running might pull the threads in the block- which would be bad.

You could always loosen the nuts & retorque them to the correct value and, if it leaks, then you really haven't lost much because you were going to have to pull the head anyway if you replaced the gasket.

[wethomas]

thanks for the help

After this eating on me for a few days, I ordered new studs, new nuts and a new gasket. Im going to take the thing apart and re assemble. Then I can get a good nights sleep.

I plan on inspecting the block holes with machinist dye to make sure there is no micro cracks. I think the fact that I did not run it will help me on this.
Torque wrench was thrown in the nearest river.

[wethomas]

Update

350 hours on a wonderful running machine, no issues, runs beautiful, never used a drop of oil. Very lucky to have found this thing

[winston]

Happy for you.