ARP Studs versus Head Bolts?
#21
04-17-2013, 04:45 PM
Stretch bolts provide a clamping force that is more likely to be sustained than a stud. The bolts are fabricated to a specific cross section so that they will begin to experience plastic (non-recoverable) deformation above a certain torque. Once you stretch the bolts elastically by achieving tension within the bolt from the initial torque, you then elongate them in the plastic range by turning them a specific amount. The pitch of the thread determines how much they stretch as they are rotated. By moving the bolts into the range of plastic deformation, you have a tensile stress locked into the bolt that will be effective even if the dimensions between the head and the threads changes slightly. A stud that is more robust and experiences much less elongation when the nut is torqued will provide much less clamping force if there are any dimensional changes in what is being clamped. We use the same principle when installing a free-stress (unbonded) length in rock and soil anchors. When you pre-load the anchor you stretch the unbonded length. If the system experiences a little movement, there will still be a tensile force in the anchor.
The problem is that the Rover block is aluminum and the area where the threads are located is not thick enough to handle the loads imposed on it. Add the stress of a fastener being rotated while being loaded and you may eventually end up with cracks or just yanking the threads out during assembly.
The ideal solution would be stretch studs. If they can work 3 times, that should be enough. After the 2nd set of head gaskets it's time to get a new motor.
The problem is that the Rover block is aluminum and the area where the threads are located is not thick enough to handle the loads imposed on it. Add the stress of a fastener being rotated while being loaded and you may eventually end up with cracks or just yanking the threads out during assembly.
The ideal solution would be stretch studs. If they can work 3 times, that should be enough. After the 2nd set of head gaskets it's time to get a new motor.
Its called modulus of elasticity.I learned that some time ago in class when younger. I would reexamine parts of your response as some of them have no merit. I'll sign out on this topic, as it is a worthless cause on the Land Rover block in stock configuration. There are just to many design deficiencies inherent with the engine/management overall.
Good Luck to all
MAK
#22
04-17-2013, 07:46 PM
Baja
#23
04-17-2013, 08:34 PM
I have no beef with anyone on the site at all. I am not sure exactly what post you are referring to. I have used the proper tools in regards to bolt stretch/mediums and all formulas regarding its applications in industry. If you read ARP's site regarding modulus of elasticity, you will have a small, but better understanding of stretch and the engineering principals for the use. In a standard block, I could care less which fastener is used after correcting the flaws. Both a stud, and bolt are applicable. Please do not include me in any more discussion of this. I have little interest in the Land Rover using the knowledge/applications when in school or my career.
Your help to others is appreciated by all, including me.
MAK
Your help to others is appreciated by all, including me.
MAK
Last edited by racerxnet; 04-17-2013 at 08:44 PM.
#24
04-17-2013, 08:55 PM
It would be interesting to note...
Why do the head gaskets go bad - in the first place at 90,000 miles or so..?
So, if I was at the Rover factory in 2001 say for my Truck.
And I had the engine builder put in ARP studs and the hardened washers..
Then wonder if my head gaskets would have lasted longer - or not.
Is there an inherent flaw in the clamping force of the stretch bolts (apparently there is not if they are in their "plastic range" which causes inconsistent clamping which ruins the head gasket?
Why do the gaskets fail at the outer cylinders near the coolant passage?
Guessing that the gasket there is the thinnest.
And - interestingly the coolant passage being there can't conduct force to distribute the load.
So, is the force concentrated between the coolant passage and the cylinder -
for example #1 which crushes the gasket thinner at that point and weakens it?
I am just guessing here.
Does that junction expand and contract a lot more than the other parts of the head then causing expansion / contraction and wearing the gasket out from motion under pressure?
This is interesting. So maybe the solution is..
Install ARP studs.
Torque.
After 100 hours retorque.
Done.
Well done guys!
Articles say that the stretch bolts MAY KEEP STRETCHING.
6.0L Head Gasket Failure
Prevent Head Gasket Failures
Message Center
Why do the head gaskets go bad - in the first place at 90,000 miles or so..?
So, if I was at the Rover factory in 2001 say for my Truck.
And I had the engine builder put in ARP studs and the hardened washers..
Then wonder if my head gaskets would have lasted longer - or not.
Is there an inherent flaw in the clamping force of the stretch bolts (apparently there is not if they are in their "plastic range" which causes inconsistent clamping which ruins the head gasket?
Why do the gaskets fail at the outer cylinders near the coolant passage?
Guessing that the gasket there is the thinnest.
And - interestingly the coolant passage being there can't conduct force to distribute the load.
So, is the force concentrated between the coolant passage and the cylinder -
for example #1 which crushes the gasket thinner at that point and weakens it?
I am just guessing here.
Does that junction expand and contract a lot more than the other parts of the head then causing expansion / contraction and wearing the gasket out from motion under pressure?
This is interesting. So maybe the solution is..
Install ARP studs.
Torque.
After 100 hours retorque.
Done.
Well done guys!
Articles say that the stretch bolts MAY KEEP STRETCHING.
6.0L Head Gasket Failure
Prevent Head Gasket Failures
Message Center
#25
04-17-2013, 10:04 PM
Recovery Vehicle
It would be interesting to note...
Why do the head gaskets go bad - in the first place at 90,000 miles or so..?
So, if I was at the Rover factory in 2001 say for my Truck.
And I had the engine builder put in ARP studs and the hardened washers..
Then wonder if my head gaskets would have lasted longer - or not.
Is there an inherent flaw in the clamping force of the stretch bolts (apparently there is not if they are in their "plastic range" which causes inconsistent clamping which ruins the head gasket?
Why do the gaskets fail at the outer cylinders near the coolant passage?
Guessing that the gasket there is the thinnest.
And - interestingly the coolant passage being there can't conduct force to distribute the load.
So, is the force concentrated between the coolant passage and the cylinder -
for example #1 which crushes the gasket thinner at that point and weakens it?
I am just guessing here.
Does that junction expand and contract a lot more than the other parts of the head then causing expansion / contraction and wearing the gasket out from motion under pressure?
This is interesting. So maybe the solution is..
Install ARP studs.
Torque.
After 100 hours retorque.
Done.
Well done guys!
Articles say that the stretch bolts MAY KEEP STRETCHING.
6.0L Head Gasket Failure
Prevent Head Gasket Failures
Message Center
Why do the head gaskets go bad - in the first place at 90,000 miles or so..?
So, if I was at the Rover factory in 2001 say for my Truck.
And I had the engine builder put in ARP studs and the hardened washers..
Then wonder if my head gaskets would have lasted longer - or not.
Is there an inherent flaw in the clamping force of the stretch bolts (apparently there is not if they are in their "plastic range" which causes inconsistent clamping which ruins the head gasket?
Why do the gaskets fail at the outer cylinders near the coolant passage?
Guessing that the gasket there is the thinnest.
And - interestingly the coolant passage being there can't conduct force to distribute the load.
So, is the force concentrated between the coolant passage and the cylinder -
for example #1 which crushes the gasket thinner at that point and weakens it?
I am just guessing here.
Does that junction expand and contract a lot more than the other parts of the head then causing expansion / contraction and wearing the gasket out from motion under pressure?
This is interesting. So maybe the solution is..
Install ARP studs.
Torque.
After 100 hours retorque.
Done.
Well done guys!
Articles say that the stretch bolts MAY KEEP STRETCHING.
6.0L Head Gasket Failure
Prevent Head Gasket Failures
Message Center
2. Yes, factory Land Rover bolts DO NOT clamp tight enough before stretching, this has been known since the 90's, the dealer I worked at switched to aftermarket head bolts to correct this problem in like 2003.
3. The ends of the heads move outward during expansion and contraction, gradually sanding off the gasket right at the coolant passages. (this expansion and contraction can/should be minimized by switching to an inline 180* thermostat) The swelling upwards of the head can also stretch any type of fastener, TTY or stud, thereby lessening the clamping force. ARP studs with yearly (or 6 month increment) re-torquing would probably work better than stretch bolts in the long run, but for the average Joe they are just not feasible, and will not offer any benefit that I can see.
Last edited by RoverMasterTech; 04-17-2013 at 10:13 PM.
#26
04-17-2013, 10:16 PM
1. Without scheduled re-torquing the head gaskets would have not lasted as long if ARP studs had been factory.
2. Yes, factory Land Rover bolts DO NOT clamp tight enough before stretching, this has been known since the 90's, the dealer I worked at switched to aftermarket head bolts to correct this problem in like 2003.
3. The ends of the heads move outward during expansion and contraction, gradually sanding off the gasket right at the coolant passages. (this expansion and contraction can/should be minimized by switching to an inline 180* thermostat) The swelling upwards of the head can also stretch any type of fastener, TTY or stud, thereby lessening the clamping force. ARP studs with yearly (or 6 month increment) re-torquing would probably work better than stretch bolts in the long run, but for the average Joe they are just not feasible, and will not offer any benefit that I can see.
2. Yes, factory Land Rover bolts DO NOT clamp tight enough before stretching, this has been known since the 90's, the dealer I worked at switched to aftermarket head bolts to correct this problem in like 2003.
3. The ends of the heads move outward during expansion and contraction, gradually sanding off the gasket right at the coolant passages. (this expansion and contraction can/should be minimized by switching to an inline 180* thermostat) The swelling upwards of the head can also stretch any type of fastener, TTY or stud, thereby lessening the clamping force. ARP studs with yearly (or 6 month increment) re-torquing would probably work better than stretch bolts in the long run, but for the average Joe they are just not feasible, and will not offer any benefit that I can see.
#27
04-18-2013, 12:38 AM
Has anyone ever re-torqued their head bolts after a break in period?...50-100 hours of driving?
I would assume that a TTY bolt if it lost its torque value you would need a new bolt and not just tighten it back up. (imagine a benefit of the bolt is a re-torque is not required in its application)
Only reason I ask is because I have read on here that when removing the heads, some of the bolts come out with no effort and others require a breaker bar.
Good information posted on here. I have been reading it all.
Thanks.
I would assume that a TTY bolt if it lost its torque value you would need a new bolt and not just tighten it back up. (imagine a benefit of the bolt is a re-torque is not required in its application)
Only reason I ask is because I have read on here that when removing the heads, some of the bolts come out with no effort and others require a breaker bar.
Good information posted on here. I have been reading it all.
Thanks.
#28
04-18-2013, 01:16 AM
RoverMasterTech
As always you have provided a very plausible answer.
Thank you.
I simply go by what I have observed from taking my heads off and taking pictures of the gaskets for a post mortum analysis on both a 1997 and a 2001.
I have always noticed the 1997 engine make more of a metallic tink tink noise when the engine heats up.
And in the garage when it cools down. That noise is of a gross contraction of metal cooling. I could not help but wonder if it is indeed the head or the intake cooling and adjusting.
As the head has exhaust gas going through it then this must create zones of expansion which would be greater than the block which does not have direct contact with exhaust gas.
I did ponder if a 180 degree thermostat would indeed cause a lower delta of extreme operating temperatures from idle to open road to idle.
I have observed my truck will have large temperature swings with the 190 degree factory thermostat from 190 going down a hill on the interstate to
211 or so in the parking lot. The AUX fan coming on in my case seems to limit the temperature to hold around 211 or 212 and go no higher at idle.
Coefficent of expansion of aluminum
22.2 (10 to the minus 6 inch/inch degrees F)
Delta for me is 190 degrees to 211 which is 21 degrees.
22.2 * 21 degrees
466.2 times 10 to the minus 6 in/in
as the Degrees cancel in the equation.
head about 2 feet long...
24 inches * 466.2 * 10 to the minus 6
11888.0 * 10 to the minus 6
So, crank the decimal point back 6 places..
Over a 2 foot head then it would expand, contract
.01188 inches with a
Which is .3 mm
Seems like a lot - .3mm.
But, if you look at a mm on a slide rule and think about how long the head is..
And as the coolant goes thru the whole engine and head, the block and head should be expanding and contracting at the same rate mostly.
but, probably not exactly..
Ah, now think of this!!!!
The engine and block ARE expanding and contracting in tandem.
the HEAD gasket IS NOT expanding and contracting with the head and block.
It is NOT aluminum....
And so as MasterRoverTech says---
It gets SANDED.
So, it will wear out - no matter what.
Under ARP studs or Stretch.
What do you think of that?
As always you have provided a very plausible answer.
Thank you.
I simply go by what I have observed from taking my heads off and taking pictures of the gaskets for a post mortum analysis on both a 1997 and a 2001.
I have always noticed the 1997 engine make more of a metallic tink tink noise when the engine heats up.
And in the garage when it cools down. That noise is of a gross contraction of metal cooling. I could not help but wonder if it is indeed the head or the intake cooling and adjusting.
As the head has exhaust gas going through it then this must create zones of expansion which would be greater than the block which does not have direct contact with exhaust gas.
I did ponder if a 180 degree thermostat would indeed cause a lower delta of extreme operating temperatures from idle to open road to idle.
I have observed my truck will have large temperature swings with the 190 degree factory thermostat from 190 going down a hill on the interstate to
211 or so in the parking lot. The AUX fan coming on in my case seems to limit the temperature to hold around 211 or 212 and go no higher at idle.
Coefficent of expansion of aluminum
22.2 (10 to the minus 6 inch/inch degrees F)
Delta for me is 190 degrees to 211 which is 21 degrees.
22.2 * 21 degrees
466.2 times 10 to the minus 6 in/in
as the Degrees cancel in the equation.
head about 2 feet long...
24 inches * 466.2 * 10 to the minus 6
11888.0 * 10 to the minus 6
So, crank the decimal point back 6 places..
Over a 2 foot head then it would expand, contract
.01188 inches with a
Which is .3 mm
Seems like a lot - .3mm.
But, if you look at a mm on a slide rule and think about how long the head is..
And as the coolant goes thru the whole engine and head, the block and head should be expanding and contracting at the same rate mostly.
but, probably not exactly..
Ah, now think of this!!!!
The engine and block ARE expanding and contracting in tandem.
the HEAD gasket IS NOT expanding and contracting with the head and block.
It is NOT aluminum....
And so as MasterRoverTech says---
It gets SANDED.
So, it will wear out - no matter what.
Under ARP studs or Stretch.
What do you think of that?
#29
04-18-2013, 01:23 AM
So my feeling is that the aluminum block / head seals the fate of the head gasket due to coefficient of expansion.
So, I messed up that calc.
Aluminum on a 2 foot head will move about .15mm. The 22 should be a 12 for the coefficent of expansion of aluminum.
Coefficients of Linear Thermal Expansion
But, check this out..
Coefficient of Aluminum is 12.
Cast iron is 6
So, the expansion and contraction of a cast iron block and head are
1/2 of an Aluminum Block and head.
So, those head gaskets on a cast iron block and head should get 1/2 the wear.
Ah, well what about the failure rate on a cast iron block and a cast iron head?
My old 1987 Saab 900 had this combination.
So, I messed up that calc.
Aluminum on a 2 foot head will move about .15mm. The 22 should be a 12 for the coefficent of expansion of aluminum.
Coefficients of Linear Thermal Expansion
But, check this out..
Coefficient of Aluminum is 12.
Cast iron is 6
So, the expansion and contraction of a cast iron block and head are
1/2 of an Aluminum Block and head.
So, those head gaskets on a cast iron block and head should get 1/2 the wear.
Ah, well what about the failure rate on a cast iron block and a cast iron head?
My old 1987 Saab 900 had this combination.
#30
04-18-2013, 07:17 AM
Baja
Riddle me this Batman,
If stretch to yield bolts are so good why is it that practically every manufacture who rebuilds these motors for a living in England use ARP stud kits on rover v8's.
Look at MOST of the sites in England like ACR, Turner and the like why do they all use ARP head stud kits? Certainly not because the like to pay the extra money for parts on a rebuild.
As you all know this is a country that treats rover v8 like small block Chevy's (disposable) so why would the all shy away from STY bolts for ARP stud kits?
Maybe because the like to admit they are wrong and have to get help from the Americans,
but I don't think so.
If stretch to yield bolts are so good why is it that practically every manufacture who rebuilds these motors for a living in England use ARP stud kits on rover v8's.
Look at MOST of the sites in England like ACR, Turner and the like why do they all use ARP head stud kits? Certainly not because the like to pay the extra money for parts on a rebuild.
As you all know this is a country that treats rover v8 like small block Chevy's (disposable) so why would the all shy away from STY bolts for ARP stud kits?
Maybe because the like to admit they are wrong and have to get help from the Americans,
but I don't think so.
