CHECKING OUR CUMMINS HEAD BOLTS AT 270,000 MILES
Cummins diesel engines are known for their insane reliability over upwards of 500,000 miles. When it comes to doubling their horsepower, however, there are a few precautions to be taken. Besides the “killer dowel pin” problem, which we’ve covered in the past but will revisit soon, Cummins engines are also prone to blown head gaskets—a problem that can happen at any time. Unfortunately, head gasket reliability depends on how warped the Cummins head has become during many years and miles of driving. We’ve seen some trucks survive at 50 psi with nitrous, while other trucks start leaking at 200 rwhp with the fuel plate removed. It’s just the luck of the draw. Even with some unknowns, there are still some things that you can do to stack the deck in your favor. After decades of use and thousands of heat cycles, head bolts lose their elasticity and the head gasket settles. This means that the head bolts that started out at 60 ft-lb and 90 degrees (about 120 ft-lb) might loosen up by 20-30 ft-lb or even more. Less clamping force also means it’s more likely that a blown head gasket will result from turning the power up, which we were about to do. The good news is that performing a re-torque, while time consuming, is fairly simple. Eventually, we’ll step up to a set of serious ARP 625 head studs and a fire-ringed gasket, but for the price (virtually free other than the ARP lube and labor), our Cummins re-torque was a pretty good deal.