Head Bolts


http://209.208.111.198/Topic75657.aspx 		Print Topic | Close Window

By 55 GLASS TOP - 13 Years Ago
I am installing new head on my car, big discussion with ny neighbor , Do I lube the head bolts and torque them 20 percent less or do I install the dry and torque them to what it says in the book. Lube or Not what is the best way to install headbolts. I expect this to be an very active question.
By Marc - 13 Years Ago
Lube. I build jet engines for a living. Every last fastener gets lubed. and torque it to spec. You just wont get an accurate torque without lube.
By Rono - 13 Years Ago
Are you using regular (Grade 8) head bolts or ARP head bolts? Reason I ask is because I am in the process of building a new engine now and I'm using ARP head bolts I got from John Mummert. There is a difference between the torque specs if you use oil on the threads vs ARP lube. With ARP head bolts using ARP lube the torque spec is only 65 ft/lbs. With oil I believe it was 85 ft/lbs.

Rono

By 55 GLASS TOP - 13 Years Ago
I am working with standard head bolts ,  I would like to lube them lightly and torque to spec.
By MoonShadow - 13 Years Ago
While the engine is down take the time to run a tap through all the bolt holes. Clean threads in the block and oil will get you the correct readings. Chuck
By matt2491 - 13 Years Ago
Should we be using oil or thread sealant?
By DANIEL TINDER - 13 Years Ago
A little off point, but what about the recommendation to use no lube on wheel lugs? While I understand losing a wheel at speed can be traumatic, I have also wrestled in the past with frozen lug nuts on wheels that haven't been off for years. I use just a smidgen of anti-sieze, and have never had a problem (at 80 ft.lbs.) with loose wheel nuts.
By charliemccraney - 13 Years Ago
There are too many variables for there to be a correct answer with limited info. Follow the advice from the manual you are reading for the torque specs. They usually tell you if that spec is dry, or lubed and what that lube is. If you don't then you risk tightening it too much or too little.



Matt, you don't need thread sealant on Y-Block head bolts so of the two, you'd use oil, but use the right torque spec!
By GREENBIRD56 - 13 Years Ago
Engineeringwise - the definition of "dry" also means coated in "light" oil. Light oil is also SAE 140 when considering the contact pressures we are talking about here.  

Thread lubricants are something like "Neverseize" or a colloidal copper compound, and moly paste - they are specifically designed to handle huge metal to metal contact pressures. They hold the surfaces apart and reduce sliding friction at pressures that would crush hydrocarbon molecules. 

For the purpose of engineering calculations the expected coefficient of friction of "dry" threads (light oil coated) is 0.20 and the coefficient of friction of threads coated with Neversieize is 0.15. So - in general - if you know the "dry" thread torque and choose to coat the fastener with Neverseize, the application torque can be reduced by 25%.

There are special fastener coatings - and very high performance extreme pressure lubricants where the torque calculations differ from what I've related above - but they aren't the everyday or automotive sort of usage.