Been a while since I did a valve job, and the new Viton valve stem seals have either a spring or an O-ring, but there's no instructions and Chilton manual doesn't mention the difference. Which is intake/which is exhaust? The existing seals all have metal springs.

 

Darker spring on the valve seals are for exhaust side while the shiny chrome spring ones are for intake.

Intake Side:



Exhaust Side: