4g63 valve stem grinding to achive specific height.

Hello, I am rebuilding evo 8 cyl head. Machine shop cut the valve seats and some valves exceeds the specified protrusion limit. For intake it is 49.70mm and some of the valves has protrusion of 50.00mm Is it ok to grind top of the valve stem by 0.30mm to achieve 49.70mm limit? The mitsubishi book says to replace the valve seat If the measurement exceeds the specified limit. What downsides will I see by grinding the top of the valve? Thanks!

The valve stem height goes together with camshaft profile and rocker arm ratio along with hydraulic lifters to ensure no disconnecting in valve train. Higher valve stems will create some pressure that would translate to excessive cam profile wear over time. So as long as you compensate lower valve seats by adjusting the valve stem height and maintain the initial ratio it's absolutely fine.

Removing material from the vlave face and/or seat will also mean less seat pressure/force from the valve springs - they will need to be checked for installed height and probably need to be shimmed.

Thank you guys for help!! Yes I will check spring install height and use necessary shims.