Re torqueing head studs/bolts

krazykuda said
No, there are two kinds of torque, static and dynamic.

Static is higher and what you call "breakaway" which is how much torque it takes to start the bolt turning.

Once it turns, then you are measuring dynamic torque, the amount needed to keep it turning, which is slightly lower.

We're saying the same thing.....BTW the extra torque needed for 'breakaway' is due to stiction which is always higher than the friction of moving. It is like sliding a heavy box along the floor: you need to put more force on it to get it moving and it takes less force to slide once it is moving.

As far as the bolts stretching, the old original types in these engines can be re-used because they are not designed to stretch beyond their elastic limit and become permanently stretched when torqued to spec. (Although some may indeed permanently stretch at times.) A lot of modern head bolts (maybe all?) are torque-to-yield bolts that do indeed permanently stretch, and are not to be re-used. Those are the ones to not loosen andre-torque...IMO.

JustinP, I'll guess that the gaskets 'settled' or flowed a bit on you. It is an interesting observation and thanks for posting it. And I suspect you are right on the thread pitch.