I have a 66 Barracuda with an original 273, never gone through as far as I can tell. has 119k+ miles (speedo broken for several years) It is using oil and smokes quite a bit at startup and under WOT, sometimes just at idle! Normally, I would assume a worn ring issue, but I did a compression check, and all 8 cylinders ranged from 135-155 psi! I swapped out the valve guide seals, there were very hard and brittle, and several crumbled. Only helped marginally. I did notice the valves moved in the guides slightly when I pushed on them. I tried some 20W50 and some oil thickener (stop smoke crap) and it may actually be worse. I really don't want to pull the engine. Perhaps just a head rebuild? How hard is it to re-ring the motor while in the car? Thoughts?