Stud Removal
While the actual manifolds on our '66 Mustang were in good shape, we can't say the same about the studs on the passenger-side manifold. Only a handful of threads were still usable on each stud, so we needed to remove them before restoring the manifolds. New studs will be installed later.
Merv Rego says there are two ways to remove rusty studs from exhaust manifolds. By heating the studs and the area around them, you can often break the studs loose with Vise-Grip pliers or a pipe wrench. This worked perfectly on one of our studs. The other one snapped off, forcing Merv to switch to Plan B-drilling out the broken-off stud. This requires some careful surgery to prevent damaging the interior threads, but by starting with a small drill bit and working up in size, you can remove most of the stud material before cleaning out the threads with a tap.
With fingers crossed that...
With fingers crossed that the studs would break loose with the application of heat and muscle, Merv heated up the area around the stud with a propane torch.
When Vise-Grips wouldn't grip...
When Vise-Grips wouldn't grip tight enough, Merv grabbed a medium-size pipe wrench. After spraying the stud with penetrate and tapping on it with a hammer, one of the studs broke loose and came right out. The other snapped off completely.
Drilling out the broken stud...
Drilling out the broken stud was the second option. Starting with a small bit and working up to a bit nearly as large as the stud, Merv carefully drilled out the stud material before cleaning the threads with a tap. With new studs in place, our manifolds are ready for another 45 years of service.