spark plugg are burnt

Valve seals are a good idea if the rings are not shot; they get old and brittle or hard and just don't seal as well anymore.

Do you have any photos of the plugs to post? This is important to see what you mean by 'burnt up'. Do you mean the electrodes are all gone? OR do you mean there is black burnt crud all over them? If the latter is the case, then the oil rings may be shot and the burnt crud is burnt oil and the adapters (non-foulers) are there for a reason.