Just a couple of things I need to learn.

1) What does it mechanically mean...
2) What causes...
3) What are symptoms of...

Burnt valves and collapsed lifters.

Thanks!

 

Burnt valves: No longer sealing cylinder pressure because of heat damage to either the valve or head sealing surface. Caused by worn guides/valve stems, sticking valves in guides, carbon build-up on sealing surfaces, or perhaps lean mixture or pre-ignition. Usually its the exhaust valves that "burn".

Collapsed lifter: Hydraulic lifter that does not properly remove valve lash when running up the cam lobe ramp. Basically, the plunger bottoms out in the lifter body instead of being "locked" hydraulically as the lifter starts to move up. Usually caused by dirt, but also may be from over-reving and damaging the lifter internals.

 

you'll see a lot of people refer to both problems when it's often something else, same with rod knock