Look for excessive exhaust valve stem clearance, and bronze-line the guides, or replace if necessary. I like to use the umbrella seals on both intake and exhaust, and eliminate the steel cap and o-ring under the keeper. If you just add an umbrella seal, you'll probably keep all the oil off the guide, and wear it out.
I've been able to check stem clearance without removing the head in some cases. Be sure the piston is at TDC, to avoid dropping a valve into the cylinder, and remove the valve spring. If you can get any noticeable wobble of the stem in the guide at the top, it's probably too worn to prevent oil consumption. Lots less work to do it that way, than pulling the head and doing a full teardown!
Jerry
