Anti-sieze or plain oil on head bolts? Opinions?

What do you guys think?

I'll probably go with the light coat of oil as Ford recommends....and yeah...I always coat the bottom of the bolt head....will take care of the exhaust manifold stuff w/ antisieze and reduce torque....

ferg

One of the other folks pointed out that you must use new head bolts. This is the most important point. Bolts tighten by elongating. Once they have, they will never torque correctly again. With most bolts, it doesn't matter. With head bolts, it makes all the difference in the world.

To get a light coat of oil, I dip the threads of the bolts in a can of clean oil and place on a rag to drip off excess. Install as normal to specified torque value.

I have also done engines where I used anti-sieze but reduce the specified maximum torque value by 10%.

I am most concerned with exhaust manifold bolts. Use a good quality high temp anti-sieze on these. In most cases, these are what will give you the most trouble to remove after years of service. I'm not very fond of using copper based anti-sieze on exhaust systems because it does not work near as well as a good nickle based one does. Once again, reduce the max torque by 10% and then check for leaks, go to max torque if needed but do this when the engine is cold (room temp). Hot torquing will cause considerable over torque of the bolts and lead to serious problems.

Most engine bolts are black finish and have a light coating of oil or other type compound to help prevent rust during shipping and storage. This is taken into account when specs are listed for most engine assembly and thus giving the bolts a light coat of oil does not change the torque specs. Anti-sieze is a different animal and will allow for less friction during assembly and does require a 10% reduction in the torque value. The "10%" is not a carved in stone hard fact but is a good rule of thumb that will work in nearly all applications.

For thread locking compounds, these are generally considered to have the same lube properties related to torque tightening as is the light oil coating and is generally not a concern however, you should check the lable for specific directions before using.