I have 4 502's ( MPI)in a Cary 50.. just repowered 2 years ago.. lost a set of valves in one motor, and the motor builder said it was due to the heads having mud in them... the heads heated up and the valves hung..
His idea was to hog out the little tiny holes in the head gaskets were the water flows thru..

Is that a good idea ?? thanks fella's

Increasing the size of the steam holes isn't a bad idea however not necessarily required in your case.

If the heads where re-built just prior to their failure it is likely the guides where to tight in the beginning.

so does that mean the other 3 engines valves are going to hang up as well? like mentioned sounds like tight guides..sea strainers should cure the mud problem.

My 1st question is, what shape was the sea water pump in after this happened?
2nd.What shape were the cylinder walls and pistons in?
3rd. Were they exhaust valves that stuck?
4th. What was the valve to guide clearance?
5th. Was a positive seal being used.
6th. Did he use a guide liner, broach it, to size or broach it then hone to size?

I have seen engine come in with lots of sand, silt, in the blocks but never go to the point of only sticking the valves. This is only based on what I have seen in 20+ yrs. These are questions I would ask, if it being me. Modify the gaskets, that I leave to a gasket expert.