You have been plagued with more than one thing going wrong at a time and still retain my sympathies. Life presents what it presents, ain't it grand?
But, i don't care much for that sticking valve. Perhaps the carburized excess
oil from the now presumed leaky intake manifold gasket has fouled the guide, as you infer. Certainly it was sticking, and it might also have had a carburized build-up on the valve seat, rather than only or in addition to the guide.
Either one of these cases bothers me a bit. i would suggest removal of the rocker, locks and springs of that particular exhaust valve #6 and ensure that it has an easy smooth movement up and down, seats in the valve seat at the proper height (measure to some convenient reference point) and rotates smoothly in all open, closed and intermediary positions.
i have two concerns: one, that the guide is still fouled and may run dry, which would lead to premature failure. Use of some marvel mystery
oil or a quality penetrant
oil (not TOO much) may help free the rather narrow guide clearance, if it is reluctant to move very smoothly. Two, that the seat seal isn't clear and could lead to an eroded valve or seat prematurely. The valve depends on proper seating to cool it, of course, and when it doesn't seal properly, it overheats, frequently causing a stem failure or pit erosion along the valve edge. Mounted in the aly head, the seat rarely overheats, but it could still be mashed by the sharp edges of carburized oil leakage (though not likely).
If you are still disassembled, make sure you are happy with the easy movement of the valve and particularly that it closes easy to the sealed position and rotates smoothly while open and closed. Designed-in rotation of the valve during operation distributes the wear accross the stem face, where it is pushed down by the rocker surface or roller. If the valve doesn't rotate properly, because of a sticky guide, it will at least wear more quickly in one place and shorten that valves usable life.
It is no surprise that it is the exhaust that is sticking, because that valve carried away the leaked and partially burned excess oil from the upper oil valley under the intake manifold.
Frankly, if you feel any roughness in the rotation or when you rotate it while closed, i would recommend head removal, guide replacement and a touch-up of the valve edge and seat.
If it were an aircraft engine, you would do this to save lives and property. While you can always pull over and call a tow truck, it could be at least expensive.
If you want to calibrate your fingers to the proper 'feel' of the smooth rotation while the valve is both open and closed, remove the exhaust springs etc. from a different cylinder and do the same exercise and measurement.
Just a thought.
Sticky valve #6
Threaded Mode
