I'm sure you have read about my 918 springs breaking. I hear that the 918 spring needs to be set up at 1.80 so I checked mine the best i could and it seems to be around 1.631. How do i change it so it will be around the 1.80? Is there differant shims i can get?

 

Sounds like the head might need machining. Installed height on the spring is how high it is off of the spring seat with just the retainer/locks installed, right? The only way to make it taller is to either machine the head down or use a thiner seat (wouldn't recommend - don't even know if they make 'em). Either that or get some valves with longer stems.