Definitive answer on ARP rod bolts on gen3 rods
02-22-2019, 09:35 PM
#22
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7k rpms on a fresh ls6 rebuild with ARP bolts and no resizing and no issues. Oil pressure rocks too.
lq9 with arp bolts on rebuild no issues for over 4 years. some people just have bad luck i guess. 
02-23-2019, 07:18 AM
#24
Stronger doesn’t exactly mean that it takes more force to stretch the bolt. Higher Tensile and Yield strength only means it takes more force to break or yield the material. The force needed to stretch a carbon steel a given amount (Modulus of Elasticity) is supposed to be constant regardless of the tensile or yield strength. The higher yield steel just allows you to stretch the bolt more in order to achieve a higher clamp load.
02-23-2019, 07:22 AM
#25
Stronger doesn’t exactly mean that it takes more force to stretch the bolt. Higher Tensile and Yield strength only means it takes more force to break or yield the material. The force needed to stretch a carbon steel a given amount (Modulus of Elasticity) is supposed to be constant regardless of the tensile or yield strength. The higher yield steel just allows you to stretch the bolt more in order to achieve a higher clamp load.
02-23-2019, 07:39 AM
#26
Im not ME but I agree about tensile strenght, but yield strength is exactly that, stretching it a certain amount. My understanding was the ARP bolts resist stretching more compared to a factory bolt.....meaning it would resist more force before deforming the same amount as a factory bolt. Maybe I'll never get it lol.
So a 150ksi tensile steel and a 200ksi steel may take the same amount of force to stretch it .100” but one may yield at .075” and the other may yield at .150”.
02-23-2019, 07:51 AM
#27
I think you’re getting Modulus of Elasticity mixed up with Yield Strength. Yield strength is the amount of force that causes the material to stretch to it’s yield point, usually expressed in psi in the US. The Modulus of Elasticity is how much force it takes to stretch the material a given amount, which maybe be psi/in.
So a 150ksi tensile steel and a 200ksi steel may take the same amount of force to stretch it .100” but one may yield at .075” and the other may yield at .150”.
02-23-2019, 06:17 PM
#28
Teching In
If you run plastigauge around the entire rod journal with new arp bolts you might be able to see if they have distorted or not. I’ve built two LQ4 engines both with arp rod bolts without honing because I saw no distortion in the journal. Both engines I’m proud to say are still running just fine. If the rods are balanced correctly and not distorted to begin with and your piston weight to the crankshaft is correct you won’t have any problems. Twisting these engines 7,400 rpms all season long.
02-23-2019, 09:21 PM
#29
Everyone wanted actual test with actual measurements and clear cut info. Thats what i brought.
Thousands run jy builds with no problems and thousands dont. Is either right? A matter of perspective. But from a mathematical and scientific standpoint, its better to hone. And i scienced the **** out of this so far.
Going for more when the weather is better. Ill have quite a few statistics.
Thousands run jy builds with no problems and thousands dont. Is either right? A matter of perspective. But from a mathematical and scientific standpoint, its better to hone. And i scienced the **** out of this so far.
Going for more when the weather is better. Ill have quite a few statistics.
02-24-2019, 01:15 PM
#31
Everyone wanted actual test with actual measurements and clear cut info. Thats what i brought.
Thousands run jy builds with no problems and thousands dont. Is either right? A matter of perspective. But from a mathematical and scientific standpoint, its better to hone. And i scienced the **** out of this so far.
Going for more when the weather is better. Ill have quite a few statistics.
Thousands run jy builds with no problems and thousands dont. Is either right? A matter of perspective. But from a mathematical and scientific standpoint, its better to hone. And i scienced the **** out of this so far.
Going for more when the weather is better. Ill have quite a few statistics.
I really appreciate the info/testing/sharing you do.
02-24-2019, 02:28 PM
#32
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Steels all basically have the same modulus of elasticity. In order to torque to higher loads, you must torque to higher strains. There is no having one without the other.
Clamping force is determined by strain and modulus. Modulus is always 29 million psi on steel, so strain is your variable.
That means to get 0.1% strain requires 29,000 psi. To get 0.2% strain requires 58,000 psi. When it yields it is no longer on the modulus. It will stretch from day 0.5% to 1.5% with little to no increase in force.
Higher yield strength bolts mean they will stay on the modulus longer in order to achieve higher clamping force. Unless they are TYY, in which case they are torqued to a particular STRAIN value which will get the bolt past yield strength. Higher strength bolts will generally fatigue FASTER than lower strength bolts, which is why you rarely see high strength TTY bolts. High strength fasteners stay below yield. Difference is you may have a 80,000 psi bolt torqued past yield or a 140,000 psi bolt torqued below yield. The 140,000 psi bolt may have less strain (stretch) but more clamping force applied since the other bolt has yielded and stretched with no added force
Clamping force is determined by strain and modulus. Modulus is always 29 million psi on steel, so strain is your variable.
That means to get 0.1% strain requires 29,000 psi. To get 0.2% strain requires 58,000 psi. When it yields it is no longer on the modulus. It will stretch from day 0.5% to 1.5% with little to no increase in force.
Higher yield strength bolts mean they will stay on the modulus longer in order to achieve higher clamping force. Unless they are TYY, in which case they are torqued to a particular STRAIN value which will get the bolt past yield strength. Higher strength bolts will generally fatigue FASTER than lower strength bolts, which is why you rarely see high strength TTY bolts. High strength fasteners stay below yield. Difference is you may have a 80,000 psi bolt torqued past yield or a 140,000 psi bolt torqued below yield. The 140,000 psi bolt may have less strain (stretch) but more clamping force applied since the other bolt has yielded and stretched with no added force
02-24-2019, 05:56 PM
#33
in talking to ARP about the need to tq their bolts to a higher spec.....their bolt material needs to stretch to achieve proper preload ....hence sticking to their tq specs
using loctite and using a lower tq is a very false application as the bolt will never reach the correct preload
also the reason for using their bolt lube for proper tq
using loctite and using a lower tq is a very false application as the bolt will never reach the correct preload
also the reason for using their bolt lube for proper tq
02-24-2019, 07:34 PM
#34
Their torque specs do not achieve proper bolt stretch though. The article i listed shows that, and anyone that has assembled a few sets with both torquing down to spec then testing stretch knows that. Normally people just torque to 1 pass full value and go. And arp really doesnt say much different ftmp but it is a good idea to always use passes. It basically prestretches the bolt but will also give you a better register on the rod caps.
3 passes is normal rule of thumb and usually you will split the total torque into 3rds or at least a somewhat even increment. Like for 45ft lbs i did 20/35/45. Since i dont have a rod bolt stretch gauge i cannot confirm they are exactly where i want to be, but im putting trust in ARP that i am close.
It has quite a few good points.
1. Use lube not dry or motor oil under the head of the bolt
2. Torquing a bolt once doesnt get you near what you want
3. Using a bolt stretch gauge is the best way
4. Pre stretching is a good way to get closer to the end goal but also allows you to set up a system for doing X rod bolts the same on an engine so you dont have to tediously measure each one.
There is alot more info in the article of course but those main points are very relevant.
I may get or borrow a rod bolt stretch gauge and test the 8740 bolts. The PRO2000s are already installed in the 333 so cant do much there.
I think i will actually. So, even more info!!
Scientce rules! #billnye
3 passes is normal rule of thumb and usually you will split the total torque into 3rds or at least a somewhat even increment. Like for 45ft lbs i did 20/35/45. Since i dont have a rod bolt stretch gauge i cannot confirm they are exactly where i want to be, but im putting trust in ARP that i am close.
It has quite a few good points.
1. Use lube not dry or motor oil under the head of the bolt
2. Torquing a bolt once doesnt get you near what you want
3. Using a bolt stretch gauge is the best way
4. Pre stretching is a good way to get closer to the end goal but also allows you to set up a system for doing X rod bolts the same on an engine so you dont have to tediously measure each one.
There is alot more info in the article of course but those main points are very relevant.
I may get or borrow a rod bolt stretch gauge and test the 8740 bolts. The PRO2000s are already installed in the 333 so cant do much there.
I think i will actually. So, even more info!!
Scientce rules! #billnye