Mine are screwed in , if Your talking about the two studs at the bottom of the exhaust manifold mine are 7/16 course thread into the manifold and 7/16 fine to the pipe I took mine out and ran a tap into the manifold and they were OK but if Yours are bad You can install Healy coils in 7/16 course they are easy to install and are very strong I also replaced the studs You can get new ones at any FLAPS.
Pete
