Main Cap Studs with Girdle. CANT FIND EM!

[Tedo44YJ]

I can not find the factory main cap studs, for the 96+ engines with the main cap girdle/brace, for the life of me . The ARP's are the only ones i can find and they only fit if you get rid of the girdle. If anyone can lead me in the right direction i would appreciate it a million!

[Cheromaniac]

I don't think that main cap girdle actually serves any useful purpose so don't worry if you can't find the studded main cap bolts with nuts.

[jsawduste]

x2 The clamping force of the ARP studs outweigh the girdle IMHO.

[Tedo44YJ]

x2 The clamping force of the ARP studs outweigh the girdle IMHO.

Ok that's kind of what I heard but I've also heard that it's for harmonics or something. Not a super high rev engine and the crank got balanced anyways. You think I'll be good without it then?

[BADASYJ]

The girdle serves a very good purpose, it strengthens the entire bottom end of your motor. Clamping force has nothing to do with the girdle or if you use studs or bolts. Studs put the stress on the stud shaft while bolts put the stress on the threads in the main webbing. Clamping force is Clamping force no matter where the stress is applied. With that being said, I think you'll be ok without it.

[Cheromaniac]

The girdle serves a very good purpose, it strengthens the entire bottom end of your motor.

I don't think the stock girdle is thick enough or strong enough to do that. Some modern engines use a bedplate instead of separate main caps and that really does add strength to the bottom end.
As far as the OP is concerned, just get the ARP main bolts and be done with it. That said, ARP rod bolts are more critical.

[jsawduste]

The girdle serves a very good purpose, it strengthens the entire bottom end of your motor. Clamping force has nothing to do with the girdle or if you use studs or bolts. Studs put the stress on the stud shaft while bolts put the stress on the threads in the main webbing. Clamping force is Clamping force no matter where the stress is applied. With that being said, I think you'll be ok without it.

Ah, no..... Bolts and studs are two different animals. The way they clamp is also different.

If they both engage the threads in the block then how can a stud not put (a) stress on the main webbing as you say ?

Why when changing to studs is almost always a requirement to align hone the mains because of the difference in clamping force ?

From one of my SAE engineering papers.

During engine assembly or maintenance, a bolt must be installed by torqueing it into place. Due to the head bolt’s design, it has to be rotated into its slot in order to engage the threads and secure it into place. This process creates both twisting force and a vertical clamping force, which means that when the cylinders within the engine’s combustion chamber begin accumulating load, the bolt will both stretch and twist. Because the bolt has to react to two different forces simultaneously, its capacity to secure the head is slightly reduced and it forms a less reliable seal in high-powered engines.

By contrast, a head stud can be tightened into place without any direct clamping force applied through the tightening. A stud can be threaded into a slot up to “finger tightness,” or the degree to which it would be tightened by hand. Afterward, the cylinder head is installed and a nut is torqued into place against the stud. The nut torque provides the clamping force, rather than the torque of the fastener itself, and the rotational force is avoided entirely. Because the stud is torqued from a relaxed state, the pressure from the nut will make it stretch only along the vertical axis without a concurrent twisting load. The result is a more evenly distributed and accurate torque load compared to that of the head bolt. This ultimately translates into higher reliability and a lower chance of head gasket failure.

The primary harmonics in the I6 family arrive from the camshaft rather then the crankshaft. The crank is supported by 7 main caps while the cam by only 5. Leee (yes 3 E`s) at Hesco has proven this well enough that he can accurately predict breakage before the engine is even started. They have experimented with adding additional journals but the it is a very costly endeavor with non conclusive results.

Again, the flimsy little metal girdle attached with a nominal fastener size does little to support the main cap integrity. One can only guess as to what the engineering team at Chrysler was trying to achieve. Their reasoning is above the knowledge of most that post on the forum.

[Tedo44YJ]

Again, the flimsy little metal girdle attached with a nominal fastener size does little to support the main cap integrity. One can only guess as to what the engineering team at Chrysler was trying to achieve. Their reasoning is above the knowledge of most that post on the forum.

Ok I dicided to ditch the girdle, especially since the only stock bolts I can find are used and they are only visually checked. ARP studs will be well worth the cost vs bolts and not having to mess with my oil pan to get it to fit.
The dealership said they discontinued the girdle and those style bolts. Must have been a good reason for it!

Question: do I need to get my mains align honed for arp studs? Is it also good to get arp rod bolts and torque flexplate(automatic) bolts as well?

[Cheromaniac]

Question: do I need to get my mains align honed for arp studs?

Not if you reuse the original main bearing caps in their original correct position.

Is it also good to get arp rod bolts and torque flexplate(automatic) bolts as well?

Yes, definitely.

[jsawduste]

Dino, have to disagree on the mains. No question on the rods. The big end always needs to be resized

At the very least the mains will need to be checked for concentric and alignment. Odds are that they will need to honed. Which should be part of a good rebuild regardless.

[BADASYJ]

The girdle serves a very good purpose, it strengthens the entire bottom end of your motor. Clamping force has nothing to do with the girdle or if you use studs or bolts. Studs put the stress on the stud shaft while bolts put the stress on the threads in the main webbing. Clamping force is Clamping force no matter where the stress is applied. With that being said, I think you'll be ok without it.

Ah, no..... Bolts and studs are two different animals. The way they clamp is also different.

If they both engage the threads in the block then how can a stud not put (a) stress on the main webbing as you say ?

Why when changing to studs is almost always a requirement to align hone the mains because of the difference in clamping force ?

From one of my SAE engineering papers.

During engine assembly or maintenance, a bolt must be installed by torqueing it into place. Due to the head bolt’s design, it has to be rotated into its slot in order to engage the threads and secure it into place. This process creates both twisting force and a vertical clamping force, which means that when the cylinders within the engine’s combustion chamber begin accumulating load, the bolt will both stretch and twist. Because the bolt has to react to two different forces simultaneously, its capacity to secure the head is slightly reduced and it forms a less reliable seal in high-powered engines.

By contrast, a head stud can be tightened into place without any direct clamping force applied through the tightening. A stud can be threaded into a slot up to “finger tightness,” or the degree to which it would be tightened by hand. Afterward, the cylinder head is installed and a nut is torqued into place against the stud. The nut torque provides the clamping force, rather than the torque of the fastener itself, and the rotational force is avoided entirely. Because the stud is torqued from a relaxed state, the pressure from the nut will make it stretch only along the vertical axis without a concurrent twisting load. The result is a more evenly distributed and accurate torque load compared to that of the head bolt. This ultimately translates into higher reliability and a lower chance of head gasket failure.

The primary harmonics in the I6 family arrive from the camshaft rather then the crankshaft. The crank is supported by 7 main caps while the cam by only 5. Leee (yes 3 E`s) at Hesco has proven this well enough that he can accurately predict breakage before the engine is even started. They have experimented with adding additional journals but the it is a very costly endeavor with non conclusive results.

Again, the flimsy little metal girdle attached with a nominal fastener size does little to support the main cap integrity. One can only guess as to what the engineering team at Chrysler was trying to achieve. Their reasoning is above the knowledge of most that post on the forum.

Ahhh, no...... Bolts and studs clamp in the same manner, by squeezing two things together. Where they differ is in how and where the stresses involved with the clamping are applied and absorbed. Which you reiterated nicely, thank you.
Obviously there is a lifting force on the main webbing threads from the stud, I didn't think I needed to clarify that.
I'll entertain your condensending question. Only because others will gain knowledge from it.
The reason an align hone is sometimes nessesary when switching to studs is because the studs do not apply a twisting stress to the webbing like a bolt would. The factory main journals are machined to account for the twisting stress applied by the bolt when torqued down. So, when no bolts are torqued down the factory mains are actually out of line ever so slightly.

[BADASYJ]

Again, the flimsy little metal girdle attached with a nominal fastener size does little to support the main cap integrity. One can only guess as to what the engineering team at Chrysler was trying to achieve. Their reasoning is above the knowledge of most that post on the forum.

The girdle was a great idea from the engineers but was ruined by the bean counters that cheaped out. Research main girdles on the google n learn something man. Instead of one single cap absorbing all the shock from the crank the girdle distributes that shock load over all of the caps, think teamwork. It is overkill on 98% of the jeep motors out there but high revving race motors do have a tendency to crack the main caps. Girdles are almost mandatory on any 2-bolt high HP motors.

[Russ Pottenger]

If you swich from a course threaded main Bolt to a fine threaded main Stud, be prepared to either line hone or line bore the block

[jsawduste]

Again, the flimsy little metal girdle attached with a nominal fastener size does little to support the main cap integrity. One can only guess as to what the engineering team at Chrysler was trying to achieve. Their reasoning is above the knowledge of most that post on the forum.

The girdle was a great idea from the engineers but was ruined by the bean counters that cheaped out. Research main girdles on the google n learn something man. Instead of one single cap absorbing all the shock from the crank the girdle distributes that shock load over all of the caps, think teamwork. It is overkill on 98% of the jeep motors out there but high revving race motors do have a tendency to crack the main caps. Girdles are almost mandatory on any 2-bolt high HP motors.

Granted I have not been in all the late model 4.0,s the ones I have all had girdles. Do I have no idea what you mean about the bean counters killing it.

If it was such an important issue with the 4.0 why did they revert to hollow main caps from the 4.2 ?

Granted SOME high performance engines Benoit from the girdle. Not so much our little 4.0 families.

BTW, it's not shock load. It's structural stiffness.

Again, I don't know where you get your info but it tends to be tainted.

[jsawduste]

The later models got a new head, ignition, OPD, exhaust, camshaft and intake manifold. Doubt the girdle amounted to much of the cost by comparison for the bean counters.

I misspoke on the main caps. The 4.2-s had the solid caps. While I've not found a material analysis however it would seem the older caps would be stronger.

If the mains were a weak spot why did the hollow caps come it in the 4.0-s ?