torque wrench and piston question

torquehouse said

Why would anyone trust a multiple-thousand dollar engine build to a $39.99 torque wrench?

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Because it doesn't make any difference. As I stated in my previous post the variation in clamping force generated when tightening a fastener to a given torque will vary up to 40%. So a $100 troque wrench with a 1% accuracy compared to a $39 wrench with a 2% accuracy is not going to matter.

As long as the force generated by the bolts is greater than the forces trying to seperate (cylinder pressure and thermal expansion) the block and head you are good to go regardless of what the torque on the bolts are. When the torque specs are developed for a non torque to yield fastener they are chosen based on inaccuracies of using a torque wrench.

If you want the most accurate wrench go get a $29 beam type wrench, they are going to be as accurate or better than any of the click type wrenches.

Making sure the threads in the head and on the fasteners are burr free, making sure the head of the bolt and it's mating surface are burr free & flat and using a consistent amount of lubricant is much much much more important than the the actual wrench you are using.

BTW, I do speak from some level of expertise, my first job out of college was developing the torquing procedures for the assembly of the jet engines used in the F14 and F15 fighters.