can coolant leak into the combustion chamber from a poorly installed cylinder head valve seat? 250 inline six, 1975 head. thank you.
ken

Yes, if they cut too deeply into the head casting it can.

Can the too deep cut be remedied?

There may be some type of sealer that can be used to reduce it or stop it. You still may want to pull the head to confirm what is causing the leak. If its a seat that's cut too deeply that's one thing, but if the head is cracked around the seat, it could fall out because of its lack of ability to hold the seat tightly enough and damage the engine.

Took the head to the machine shop. Magnaflux, no cracks. Pressure check, leaking valve seat. The machinist said the seat was cut too deep and they will try to fix it. Thank you.

Ken