ARP lube on stock head bolts

[Sinsectan]

I've recently just installed the heads on my truck, and come to find I may have made a critical mistake out of habit.

When I've done heads on different engines before, I've always used ARP head studs and ARP fastener lube on the threads and washers. However, this time I used OEM replacement Mahle bolts, but still used the ARP lube since I've never done it a different way. Looking into it more, the stock bolts I used may have overstretched. Maybe even over-crushing the head gasket.

The truck hasn't been started yet since installing. Can anyone confirm or deny if what I did is going to be a problem? Maybe I'm overthinking it.

TIA

 

[Nero]

Did you torque it to the factory spec? If you did I wouldn't worry about it too much.

 

[Sinsectan]

Did you torque it to the factory spec? If you did I wouldn't worry about it too much.

Pretty much, went to 105 ft-lbs

 

[Nero]

I always lube head bolts with fresh engine oil before install, ARP lube is just fancy lube. I wouldn't sweat it since you used the correct torque for the bolt you used.

 

[frankenwrench]

I made the same mistake back in 2017 on my 91 f250. That 7.3 is still putting today. And I'm mean to her as far as working her. Even threw a 093 turbo on it and a maxed out stock ip

 

[Sinsectan]

Sounds like I'll be alright, thanks guys

 

[FrozenMerc]

Here is a bit of info about fasteners and torqueing them.

When you torque a standard bolt (non torque-to-yield), ideally you are stretching that bolt enough to generate a clamp load equal to 85% of the bolts proof strength. Proof Strength on a 1/2" grade 8 bolt would be about 17,000 lbs. Since it is very difficult to measure clamp load on an installed bolt, we use applied torque, a much easier quantity to measure. The problem is that clamp load is a product of both torque and FRICTION. It is easy to see dramatic and sometimes dangerous swings in clamp load due to small changes in friction. Adding a friction modifier such as lube or grease onto a bolt can drop the friction and cause the clamp load to rise, sometimes to the point that the bolt yields (which causes a drastic reduction in clamp load), or even fails.

I have seen 1 1/8" bolts come apart during assembly because the manufacturer packaged them with a rust inhibitor (light machine oil) and did not notify us. The extra bit of oil was enough to drop the friction and exceed the tensile strength of the bolt during assembly. That size bolt pulls over 100,000 lbs of clamp load when torqued to just over 1000 ft-lbs. When they come apart, they will blow a 40 lb. 1" impact wrench out of the assemblers hands.

I am not saying that the OP made a mistake by using the ARP lube, I just want people to be aware of what happens when you change the friction on a bolt. Just wire brushing a bolt to clean it up and removing the Zinc & Yellow or Phosphate coating can drastically alter the friction. I have been fighting with fasteners for over 20 years in my career as a mechanical engineer. Most people have no idea the amount of resources that OE's put into fasteners to ensure repeatability and consistency during assembly.