Front cam bearings are known to fatigue and chop out the babbit. With lash adjusted you will get comp reading but when running timing gears will force cam up and close clearances on no1 cyl. Open clearances about .010" over standard and see if it runs better. If not cam brg is ok, follow up vacuum leak at manifold, booster, etc. Wiping finger around exhaust outlet will tell you if engine is using oil.