These long exhaust nuts are required when using many different Chrysler original exhaust manifolds. When using our #1390041 Exhaust manifolds, they require 2 per manifold (4 per complete engine). They are 3/8" Fine thread internally.
This is the correct stud to utilize on your Big Block Engine, not only in truck applications but also cars. They come the correct length to work with most all cast iron exhaust manifolds and 12 are required for a complete engine installation. They are the correct coarse thread length for the cylinder head and the correct fine thread length for the attaching 3/8" fine thread nut or #4041150 Long Exhaust Nut.