snarlofdisgust

My manual lists the torque spec for the crank bolt as 148ft lb, then 1/2 turn but specifies (bolt oiled)

What is it referring to? Do I literally put some 10w on it? Or is it referring to some loctite red?

Confusedly Yours
-Teh Noob

Edd W

It means the torque spec is for a bolt which has lubrication on the thread and under the head of the bolt. The actual force a bolt excerts from a set turning force (torque) is a result of many things - thread pitch, types of metal involved, bolt design, whether there is a washer etc...

If the thread is dry, it will create more friction as it tightens causing a torque wrench to display that a specifc torque has been reached but the actual clamping force the bolt is excerting will be less than if the thread is lubricated and there fore turns more easily along a higher clamping force to be reached before the same torque is applied to the bolt.

This is the reason why many bolts often now have am initial torque setting, which is relatively low and less effected by a dry or wet thread, then a number of degrees rotation, usually in 1/4 turns before it tightened correctly. This is a method which is usually used with strech bolts. This is where the shank of the bolt is machined to a precise diameter to allow it to stretch under load and end up applying the correct clamping force.

When lubricating the threads, be careful not to fill the hole into which the bolt goes because this can caused a hydraulic lock. This can do anything from not being tightened properly, through to stripping the thread or even splitting the block/head!

PS - I would expect our resident expert 4Driver4 to add at least one caveat and some additional insight to my post!

snarlofdisgust

So very very lightly coat the bolt with oil, then wipe most of it off so it only has a oil sheen? Weight of the oil matter?

A6Gary

The oil lubricant can be any oil. The purpose of the oil is to reduce friction (aka friction coeffcient) during tightening so that the variation in the preload is reduced, i.e., more of the tightening torque is applied to the preload, and reduces the twist on the bolt shank during tightening. So, put some oil on the threads near the end, run your finger around the threads to spread the oil slightly, and then thread the bolt into the crankshaft. As you turn the bolt, the oil will be distributed evenly across the threads. By the time you get to the "plus 180 degrees", the threads that are the most hightly stressed will be well lubricated.