I had an early model 283 V8 which did the same as what you say your 216 is doing. I was young and dumb (now I am not as young smile ), and replaced the heads with a set from NAPA. It made no change in the excessive oil consumption at highway speed. I am guessing the problem was from worn out rings

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission