st-customs

Ok I understand that head studs have better clamping force over head bolts, but to me they ultimately seem like the same thing. Why is one better than the other?

Nick 2K2 SS

iTrader: (2)

When you tighten a bolt down you are not just stretching the bolt in the axial direction but you are also inducing a twisting load into the shaft of the bolt because the head is attached to rod that you are trying to stretch.
On a stud set up when you turn the nut to tighten it, the stud is only stretched along it's axis and you don't induce a twisting load into it because the stud is free to relax radially.
Also when you are torquing the nut, the only resistance you have to tightening it is the surface friction on the under side of the nut and the force required to stretch the stud (which is what we are trying to accomplish anyhow to provide the clamping load). When you are torquing a bolt you have the additional resistance from the twisting resistance of the bolt shaft. So in the end you can more accurately torque a stud set up better than a bolt set up.
One other point to mention from what I have read is I think the nuts used in a stud set up have a slightly larger surface area on the underside so your clamping load is distributed over a larger surface area offering a slightly better clamp on the cylinder head.
Hope this helps you.

Wesmanw02

iTrader: (4)

Couldn't have said it better myself.

Note that with head studs though, once the engine is installed, you will not be able to remove the heads without dropping the engine out.

Nick 2K2 SS

iTrader: (2)

Is it possible to remove the studs on the rear half of the engine and then remove the heads? Or would you need to remove all of the studs in order to remove the heads from the car? The studs have a allen wrench keyway in the end of them so you can remove them like you would a bolt correct?

tom falco

The reason studs are better is also because they normally have fine threads on the top side. Fine threads torque more evenly and precise. I build 2.3 ford turbo engines and if you dont stud them its all over. Weather a stud or a bolt they both accomplish the same thing. They stretch. Basically that is why TTY came about. Bolt engineers wanted a specific clamping force at a point before bolt failure. This is why you torque to a low figure and TTY the rest of the way. TTY eliminates all the torque twist error and dirty threads ETC. Very fiew head bolts are not TTY.

Monte LS....1

iTrader: (3)

Here's the part I don't inderstand then. TTY stuff is in theory one use then throw away. Some manufactures though provide measurements and then different torque procedures to reuse a bolt that's TTY. Also, if you still have to meet an initial torque with a torque wrench, how is it that much more accurate then just using a larger torque number and be done? Is the chance of an inaccurate reading lessened due to the lower initial torque and that's why they use it?

tom falco

Ok here is the deal. TTY bolts are one time only period. Most torque wrenches are innacurate. And by using a low number evens out the field. Its easier to get a consistent reading on a lower scale then on a higher scale(friction losses.) TTY bolts will stretch and hold and you need fiewer bolts to hold the same load. TTY bolts do not have to be retorqued and should not be. There are 4 phases a bolt can go through. ELASTIC this phase stretches the bolt and the bolt can be reused . PLASTIC is between elastic and sheer or YIELD POINT. and naturally SHEER is a bolt failure. Hope this helps TOM

st-customs

thanks for all the input. i just couldnt for the life of me figure it out.

tom falco

No worrys my pleasure. TOM

Monte LS....1

iTrader: (3)

I also that TTY were throw away after one use. Just for arguements sake though, check out the head gasket replacement procedure on a honda civic, in which I did opt to use new head bolts though. Honda give's a measurement and if the head bolt hasn't stretched to a certain extent honda says use it and you torque it the same as a new bolt plus another so many degrees. Not sure if any other manufactures do this, just one that pops in my head.

tom falco

Hi MONTE i definately know about honda head bolts. Here is one of my honda sleepers. 269 front wheel HP

tom falco

Just for the record when buying a torque wrench always buy the best. The dial unit is the best. I check all my wrench for accurracy every time i use them. Here is me torquing the head on my supercharged HONDA (billy Jack)

The Alchemist

iTrader: (19)

That is absolutely 100% wrong. I've pulled and replaced heads 3 times with the studs in the block, in the car. What you might be thinking is once the head is on the block, you can't install the rear lower studs on the passenger side because of the heater core interferance.

Wesmanw02

iTrader: (4)

I don't have head studs, but I was told there wasn't enough clearance to get the heads off the studs while the engine is still in the car.

Good to know.

The Alchemist

iTrader: (19)

You most certainly can remove and replace heads with the studs in place. It's good knowledge to have. I have head studs as well as a buddy of mine, and have pulled my heads twice, and his got swapped a few months ago with no problems.