A method of detecting a gap between a valve seat insert and a port in a cylinder head may include heating the valve seat insert and the cylinder head and generating a thermal image of the valve seat insert and the cylinder head at an interface between the valve seat insert and corresponding port in the cylinder head housing the valve seat insert. The thermal image may be evaluated to determine the magnitude of a gap between the valve seat insert and the cylinder head based on a temperature at the interface between the valve seat insert and the cylinder head.