???

 

maybe on the 02 sensors but thats the only thing i can think off.

 

not on the actual block its self

 

idk i never did. just make sure when u pull the old header off wipe the gasket off and any crap thats on it and clean the outside of the head off where everything was ya know. just to make sure no dirt or any garbage might hold it up from sealing all the way.