Head Bolts Vs Studs

[Mustang5L5]

Is there a reason to not use studs? From everything I read, studs are the way to go, but what am I missing?

Can a head be pulled in-car with studs? Possible to remove the studs after the fact with the Allen and pull the head then? Of course, would be ideal to never cross that bridge.

I'm assembling the engine out of car. Anyone know the correct p/n for the TFS170s as I see quite a few kits and want to order the right one.

 

[Steel1]

A while back I did a head swap just prior to installing a supercharger on my original 302.
This was all done in the car so my plan was to remove heads and corresponding head bolts.
Then install studs and plop heads/gaskets over studs, you know NHRA style, but couldn't get
the drivers head over the back studs. Oh well, had to put studs in after head install.

 

[65ShelbyClone]

What sort of build are we talking about? I'd just use good bolts with a production block.

 

[JD1964]

I don't remember any complications when I installed head studs on my 302. One thing is, the threaded part that holds the nuts is finer thread than the portion that goes into the block. So torquing was a very smooth process and the lube was identical on all pieces. If you use head bolts, you would be putting thread sealer on the water jacket bolts, and oil on the others. So, I think there's a slight potential for resistance to be different between bolts with thread sealer and bolts with oil. For this reason, studs barely win for complete consistency in the torquing process. Mainly because all the nuts are lubricated the same during the installation process.

 

[Mustang5L5]

I ended up buying bolts. I read the pros and cons and decided for my needs, ARP bolts would work fine.

 

[Chuckman]

Studs are more "stable" in a high-pressure (boosted) application, other than that (or clearance issues like in my build) its builders choice. With the 302 you can still get the heads over the studs in the car though that may be a pain with heavy iron heads (arp ones still have a hex drive so you can install/remove with heads in place if needed). I used bolts with my 302s, and if it wasn't for the aforementioned clearance issues I'd be using them with the 427.

 

[Boostedpimp]

Don't remember anything bad about doing the studs on my motor. Made it easy to line up the gaskets and plop the heads down and torque

 

[Hoytster]

Not to get too technical, but just to reinforce what Chuckman said, a stud is inherently more stable and produces a more evenly distributed load and a more accurate torque reading. A head bolt has to be rotated to engage the threads and apply a clamping force. Since it has to be rotated, you induce two different types of forces into the fastener, a twisting force and a stretching force. Since the bolt has to react to two different forces, overall clamping force is reduced. Also, anywhere the bolt has resistance (engaged threads, washer under the bolt head, ect) will effect the final torque reading.

A head stud is rotated to engage the threads also, but it not applying a clamping force yet since you are only rotating it into the block and they usually only get finger tightened. Now, the cylinder head gets installed and the nut gets torqued on the stud. The nut now provides the clamping force instead of the torque of the fastener and any twisting force in the stud is eliminated entirely. The stud only stretches along the vertical axis instead of twisting and stretching as in a head bold. This leads to a more accurate torque reading, evenly distributed clamping forces across the head, and a higher capacity fastener.

Remember to always think of a head bold/stud as a spring.

In my experience, I had never needed head steads on a street N/A built 302, I have always used ARP bolts with no problems. If I was going boosted or extremely high compression, then I would look into head studs. But I haven't priced a set of head studs for a 302 lately, if they are anywhere close to head bolt cost, go studs.

 

[Mustang5L5]

But I haven't priced a set of head studs for a 302 lately, if they are anywhere close to head bolt cost, go studs.

$50 for bolts vs $130ish for studs.

Just a simple street N/A 302, so I went with the ARP bolts. I used the difference to buy additional ARP bolts and gaskets i'll need like intake bolts and a oil pump drive shaft.

 

[Davedacarpainter]

Not to get too technical, but just to reinforce what Chuckman said, a stud is inherently more stable and produces a more evenly distributed load and a more accurate torque reading. A head bolt has to be rotated to engage the threads and apply a clamping force. Since it has to be rotated, you induce two different types of forces into the fastener, a twisting force and a stretching force. Since the bolt has to react to two different forces, overall clamping force is reduced. Also, anywhere the bolt has resistance (engaged threads, washer under the bolt head, ect) will effect the final torque reading.

A head stud is rotated to engage the threads also, but it not applying a clamping force yet since you are only rotating it into the block and they usually only get finger tightened. Now, the cylinder head gets installed and the nut gets torqued on the stud. The nut now provides the clamping force instead of the torque of the fastener and any twisting force in the stud is eliminated entirely. The stud only stretches along the vertical axis instead of twisting and stretching as in a head bold. This leads to a more accurate torque reading, evenly distributed clamping forces across the head, and a higher capacity fastener.

Remember to always think of a head bold/stud as a spring.

In my experience, I had never needed head steads on a street N/A built 302, I have always used ARP bolts with no problems. If I was going boosted or extremely high compression, then I would look into head studs. But I haven't priced a set of head studs for a 302 lately, if they are anywhere close to head bolt cost, go studs.

Great explanation

 

[FastDriver]

Bolts worked on all 3 of my n/a builds.

 

[monte87]

ARP bolts, get my vote!!!