Hope this might help. I had my '62 409 engine rebuilt at the machine shop and it was started and dynode for a break in and adjustment purposes. Sounded great. Previously, advised the machinist to do what it takes to make the engine correct. Never limited the money invested. No budget. Just wanted it right. Short story, brought it home and installed it. Sounded and ran great, but noticed it was using about 1 quart of oil every 300 miles or so. Not leaking it. Talked to the machinist and tried many different remedies. Nothing worked. Two thousand miles later, still using oil. Checked both tail pipes and there was a dark black substance, quite heavy, in both pipes. This certainly was motor oil. Tried to figure this out on my own and thought that the oil was coming from the top down, not the bottom up. Then decided it had to be the valve guides and/or seals. Asked the machinist if he changed them and he said no. They looked good. Wrong. Took the heads off and had him install new valve guides and seals. Put the motor back together and problem was solved. No more oil usage. Can't begin to tell you how disappointed and disgusted I with this issue, especially since I didn't limit him to a dollar amount on the rebuild. Valve guides are cheap in the scheme of things. So, that's my story.