dimples on EX valves
 

I went to pick up a pair of cylinder heads for a 92's 300ZX at a machine shop. there was a MB 6 cylinder aluminium head sitting on top of another bench. Just curious...I flip it over and noticed two of the EX valves'(#2, #5) surface have little dimples on them but the rest of them are still fine(those fine circular lines are still visible). Any idea what contribute that...bad injectors??:confused:

I need a better description of the dimples. How big around,how deep, and do they look like they they were hit by debrit?

They are about the size of pinhole scatter over the valve surface. some area where they are concentrated look like the top layer is peeled off and feel like 800 grid sand paper.

Color(a little pink) of those valves look normal to me and they both have some corbon deposit on top....

Usually by Caterpillar's reuseability guide, any marks like that in ex. valves mean they are not reuseable. Intake valves can take more because they run cooler.

It sounds like debrit got in the cylinder and was pinched by the piston and exhaust valve.