How can I deal with head or manifold studs which fail to hold the specified torque values (35 foot-pounds for the head, and 25 foot-pounds for manifolds)?
There are several methods of dealing with studs which will no longer hold proper torque, depending on how badly the threads in the block are damaged: 1) If you stop torquing as soon as a particular hole starts to feel “soft”, you could re-tap to 10 mm coarse threads and install one of our 10mm head studs. The 10mm tap is the largest tap that will go through the original holes in head, which means that this technique could be used without removing the head. Our 10mm studs are machined so as to retain 3/8″ fine threads on the upper end. 2) Unfortunately, by the time a stud is felt to be failing, it is usually too late for the 10mm solution. In these cases, it is necessary to remove the head and re-tap the failed holes to 1/2″ by 13 (coarse threads), and to then install one of our thread repair bushings (product number OBLK_09_114). NOTE: See below for “text-only” instructions to assist in installing these bushings. 3) Helicoils can be used in place of solid repair bushings; however, it i
