What is the advantage of head studs?
 

What is the difference between head bolts and studs? I know one is a threaded rod the other has a hex or some other head.

Are head studs a higher grade of material, grade 8 vs 5 and therefore stronger? Why not just use a higher grade bolt?

Are they larger in diameter so that you have to drill and tap the holes?

Studs are usually a stronger material, thus providing greater holding strength. Whether or not they are the same size depends on which ones you get.

So why not use stronger bolts? With studs you would also have washers and nuts, more parts.

I am no guru, but I think it has something to do with more precise torque when using studs as opposed to bolts.

In 1983 Smokey Yunick released his book "Power Secrets". He discribed the advantages of studs in the following way: "Heads are flexing with regular bolts due to the play in between the bolt thread and the block thread. This flex is transferred to the bolts and as the bolt loosens up, the head moves even more. High grade headstuds eliminate this problem completely."

A stud is missing the weak point: The head of the bolt.

Common head bolt are usually made of the highest grade of material 12.9 or higher.

ARP bolts, for example, are made of a very high grade steel. Which isn't easy to work with. Those threads aren't cut into the bolt by a lathe, those threads are rolled in the bolt to achieve a higher strength than cutting the threads into the material.

This process costs a lot of money- ARP bolts aren't a bargain. But they provide saftey and peace of mind.
Using studs or bolts depends on the application.
High performance studs or bolts have a predictable amount of stretch. If you follow the recomandations of the manufacturer ( using oil or grease as recommended) you can apply torque to the head very precisely.

---AutoMerged DoublePost---

Automotive industrie calculates with 1/8 cent. Anything not really necessary is strictly avoided.

studs are threaded on both ends. one end thread in the block, the other requires a nut.

because it dosnt have as much rotational force, it offers more clamping force. plus they are made of better materials so they are stronger.

if wanting to run high boost levels studs are neserrary so that you dont blow head gaskets

Yep, studs are the way to go. I put them in every engine I build. I liken it to building a house.....cheap out on the interior paint, but not the foundation and studs for walls.