Main studs vs cap screws.....

[Cranky]

Btw, a cap screw is what the stock main cap 'bolts' are. Same with head bolts. Question is, is the load applied different with a stud vs a bolt uh cap screw and if so, where and how. I know the studs are usually stronger than a grade 8 cap screw screw but in my experiences, it's the nut that gives up after each and every torque cycle. Whenever I built a street engine, I threw away the old nuts that were used on the rods and went back with new ones....

 

[RemCharger]

You want to put main studs in, without honing the mains? Is that where you're going with this?

 

[toolmanmike]

Btw, a cap screw is what the stock main cap 'bolts' are. Same with head bolts. Question is, is the load applied different with a stud vs a bolt uh cap screw and if so, where and how. I know the studs are usually stronger than a grade 8 cap screw screw but in my experiences, it's the nut that gives up after each and every torque cycle. Whenever I built a street engine, I threw away the old nuts that were used on the rods and went back with new ones....

I'm sure there have been studies. Think about how cap screws mess with carb threads in a aluminum intake and how studs don't pull the threads at all. Besides, I like the fine threads on the nut side. Easier to get to the proper torque.

 

[R413]

The bolts need to be lubricated, not dry, or and brown rust or foreign material on them. Holes shall not have liquid of any kind in the bottom. Oil/coolant.

Rod nuts are special, the threads are rolled and not cut. Machinist says replace both if a problem with either the stud or nut.

 

[Cranky]

You want to put main studs in, without honing the mains? Is that where you're going with this?

Uh no but ran across this today when looking up some info on the subject and just wondering where he inserted comes from.....and this is what he said about it. The second sentence is what baffles me a bit........

"The biggest improvement you can make on any stock block is main studs. The RB blocks being as weak as they are will benefit more so than most. With studs the caps are being pushed into the block instead of being pulled like with bolts. This destrsses the main area of the block where RBs have problems."

I'm sure there have been studies. Think about how cap screws mess with carb threads in a aluminum intake and how studs don't pull the threads at all. Besides, I like the fine threads on the nut side. Easier to get to the proper torque.

I've seen guys pull the threads out of aluminum using studs too. There's always someone out there that can break the unbreakable....lol

 

[toolmanmike]

Uh no but ran across this today when looking up some info on the subject and just wondering where he inserted comes from.....and this is what he said about it. The second sentence is what baffles me a bit........

"The biggest improvement you can make on any stock block is main studs. The RB blocks being as weak as they are will benefit more so than most. With studs the caps are being pushed into the block instead of being pulled like with bolts. This destrsses the main area of the block where RBs have problems."


I've seen guys pull the threads out of aluminum using studs too. There's always someone out there that can break the unbreakable....lol

 

[sam dupont]

A screw because it is a simple machine? That must go back to the first days of automobiles. I don't see how the cap and stud apply force differently. Aren't they both trying to stretch the shafts?

 

[Cranky]

A screw because it is a simple machine? That must go back to the first days of automobiles. I don't see how the cap and stud apply force differently. Aren't they both trying to stretch the shafts?

On a stud, you have fine threads on the cap end so the root diameter of the stud is thicker than it would be if it had course threads....but, it still has course threads on the block end.

 

[lewtot184]

Studs are generally used on high maintenance stuff to keep from wearing out the threads in the machine. Fine threads don't back out like coarse threads. ARP main studs have a higher tensile strength than their bolts do but can screw up crankshaft end play. Line honing the block for studs is stupid in my opinion. Caps only need a little relieving in the bolt hole for studs. In my opinion studs, bolts, or widgets the cast iron main cap is the problem. I think girdles are stupid on a "y" block. I've used bolts and studs, and would never do a girdle. Don't trust any bolt, stud, or girdle to save the bottom end of a weak design. Change the caps and reduce reciprocating weight.

 

[Cranky]

Here's the link to the thread on FABO and it was post #5 where the member said what he did.....

What hp are mopar 440 stock main bolts good for

When is it necessary to install arp studs in the 440 lower end mains building mild street 440 will stock bolts hold up ?

www.forabodiesonly.com

 

[zyzzyx]

With cap screws or bolts, you can only safely achieve a certain torque value. With a
stud that has a fine thread on the nut end, you can achieve a higher torque safely.
The main reason for using studs on an engines mains are more holding force to keep
the caps from fretting at high RPM. At high RPM, the caps like to actually "Dance" on
the surface and fret the surfaces of the block and cap. If you're not going to rev the
DogPoop out of the engine, they're a waste of MooLa! My 440's main bores were at
the high limit, so the block didn't need honing after installation of the studs, but I
checked it by torquing down the studs and measuring the bores. If your bores are
on the tight side, you might need to line hone the block after installing them. ARP
main stud torque is 110 Foot/LBS, and that along with the threads being a fine pitch
adds alot more holding force!

 

[steve340]

I read somewhere that a stud will give better "clamp" of a component.
I do use them because on certain engines you can strip the block threads winding in a head bolt to get the torque reading. The studs are easier in the threads as the bolt is winding and tightening at the same time.

 

[Geoff 2]

The most important benefit of a stud has been missed. They screw in further which has two benefits:
- more thread surface area to distribute the load
- less distortion of the surrounding metal because of more uniform loading

 

[65CopCar]

A big advantage of a stud is that you are not twisting the fastener shank when torqueing, so you have significantly improved torqueing accuracy. Remember, you are shooting for generally around 70% of fastener proof yield with your torqueing process, and unless the stretch is measured (or some other means is used), its just a guesstimate with a torque wrench. And during the process, the threads that you are screwing into get less abused with studs.