ARP, is a company known as a leader in the fastener industry. They are by far a “go to” company for engine builders around the world. With the company’s sole focus on fasteners, it makes complete sense that they would develop additional products to ensure the proper use of fasteners.

When they decided to dive into assembly lubes, they didn’t just come up with some run of the mill product that works so, so. Their reputation as a leader in the industry is at stake every time they create a new product. So, over a two year development process and after thousands of tests they have created their Ultra-Torque fastener assembly lubricant. It has been around for years now, but do you know how important it is to use it and how they developed it?

The Issue

When torqueing something down, there are quite a few forces involved. There is a resistive force from the friction between the surface of the bolt or stud and the object it is in contact with (block, head, cover, etc). There is, also, a resistive force coming from the stud itself as it is literally stretched (the primarly cause of the preload). There is a resistive force between the stud threads and the nut being rotated.

If everything is dry, the friction forces can be quite high. These forces effect the amount of force being put on the stud. This can and often does result in an improper preload on the bolt.

More precise preload

To get around the issue of friction, assembly lubricants are used to reduce all of these friction forces. By reducing the friction, the desired force can go into the stud and a more accurate preload can be achieved.

Testing

The test equipment that they use is ultra precise. The Micro Controls MC911 data logger has an electronic motor controller for precision torque control, the electronic load cell has an accuracy of less than 0.5% to record the preload and the electronic torque transducer is capable of recording angles within 0.25% degrees. Heck, even on our best day, we couldn’t see 0.25% of a degree. I’m not even sure we could measure 25% of a degree, 100 times their accuracy.

Anyways, back to the testing. With the extremely precise testing equipment, they set out to develop a lubricant to help reach preload easier and more consistently than not using anything or using other lubricants that are currently on the market.

ARP tested their ARP Ultra-Torque, Oil, Moly and EPL (extreme pressure lube). Their initial testing was conducted with a target load of 18,000 inch pounds. The oil, Moly and EPL all resulted in much lower preloads. It takes 6 repeated cycles before the EPL achieves the acceptable range and Moly takes 7 cycles and the oil took 8 cycles. This test was done at 120 ft-lbs of torque.

Then they redid the test, but this time used the average readings gathered from testing 10 studs with each lubricant. Note, how poorly oil did during this test, routinely yielding less than 14,000 in pounds of preload. That is almost 25% less preload than what the application called for. Now, just try to tell us that wouldn’t be a major contributing factor to a failure.

Diesel testing

With diesel torque ratings being as high as they are; ARP, also, tested the most common lubes used in diesel shops. Those were oil, Moly, Detroit Diesel #2 (Peanut Butter) and ARP Ultra-Torque. The first round of testing was done at 210 ft-lbs. The huge standout here was the stud failure after 5 torque cycles by the Detroit Diesel #2 lube. This was caused by excessive preload.

The rest of the lubricants leveled out around 28,000 in pounds after 7 cycles, but generally, people want their studs to be torqued down right the first time. We here at Diesel Army, don’t like to torque down a head gasket 7 separate times before we call it good. We crush it once and hope it holds.

The next round of testing takes the stud much closer to yield with a preload of 32,000 psi. This round of testing was done at 245 ft-lbs of torque. Notice how low the initial preload was for oil. 24,000 psi is 25% less than the desired load. This can certainly lead to head gasket issues…

Conclusion

The moral of the story is that the assembly lubricant that you opt for can make a substantial impact in the reliability of your engine. Engine manufacturers specify a specific torque rating on bolts because they anticipate a certain preload on those bolts. If you are only preloading the bolt to 75% of what the engineer feels is necessary; you remove a lot of the safety factor that the engine was designed with. This could certainly result in failure of a performance engine that uses factory torque specs, but even a bone stock factory engine could have issues.

Sometimes, it is the little things that people overlook when building an engine that can make all the difference in the world.