Method #2
In talking with a few other high horsepower head bolt guys, we found that some of the more serious racers use a different torquing procedure. After letting the truck sit overnight to where it is completely cold, they'll take out one bolt at a time, coat it in oil, then torque it in 5-10 pound increments to 125 lb-ft. Oiling the bolts gives them a friction advantage over stock bolts that may have burned off all their oil, and it also makes sure all the fasteners are clamped down evenly. We took a couple bolts out of Rust Bucket to check to see if any were oiled, and some of the middle bolts were, but the exhaust side bolts had long since gone dry, which explains why they didn't turn as much. It takes much more torque to turn an un-oiled bolt than an oiled one, so if you really want to do it "right", we'd suggest this method.
Proof Load and Yield Strength
Give yourself two points if you know what these terms mean. We were kinda hazy on the subject until we started researching our head bolt dilemma. We'd heard horror stories of people breaking bolts, so we double-checked on the proof load of our grade 12.9, 12mm head bolts. As it turns out, the bolts were rated at 123 lb-ft of torque at 90% proof load when being torqued with SAE 10-weight oil. What is proof load? It is a measure of when a bolt will start to deform and stretch, and is usually a 90% value of the bolt's yield strength-the value when it finally gives way and loses its clamping force. We found the actual minimum number when a grade 12.9, 12mm bolt should start to give way to be about 151 lb-ft of torque. Since non-oiled bolts can see a torque reading of about 20% higher than oiled versions, we felt pretty safe that we weren't damaging anything by torquing ours down to a "mere" 120 lb-ft un-oiled.
 Next we torqued all the bolts...  Next we torqued all the bolts to 100 lb-ft and marked them. Make sure to use smooth, even pulls with the torque wrench. It also sometimes would take more than 100 lb-ft to break the bolt loose, so the wrench would click once when the bolt started turning, then when it clicked again we would stop. The guys at Big Power Diesel have tightened many a head bolt, so they are familiar with how they are supposed to "feel." |  After our initial cycle, we...  After our initial cycle, we then marked all the head bolts so we could see how far they turned. We went straight down the engine when we torqued ours, but if you are backing bolts off and oiling them, we'd suggest the factory Cummins pattern. |  We were able to access all...  We were able to access all the head bolts on our 12 valve except for this last corner bolt, which required draining some coolant and removing this line. |
 After our first jump to 110...  After our first jump to 110 lb-ft, some of the bolts had just barely turned, while others were close to a 45-degree angle. |  After our final jump to 115...  After our final jump to 115 lb-ft, then 120 lb-ft, we saw some head bolts at about 90 degrees. Since they were still all within a quarter turn of each other, we called it good and started to put things back together. |  Our valve cover gaskets were...  Our valve cover gaskets were thrashed, which partially explained our truck's numerous oil leaks. |
 With new gaskets in place,...  With new gaskets in place, we were ready for everything to go back together. |  Cummins uses three different-length...  Cummins uses three different-length 12mm head bolts. Since the longer ones will stretch more, they will usually turn a little more to reach the desired torque specs. We had all three sizes on hand in case one of ours stretched too far. We'd like to thank Keating Machine for supplying the bolts. |  Now it was time for our fuel...  Now it was time for our fuel lines and intake horn to go back, and now that our head is on straight, it's time for a turbo upgrade and some nitrous! Stay tuned. |