66 Olds Delta 88- I found it parked in my then girlfriends Dads garage- Lovely, 10 years old, 2 door hardtop, buckets and floor shift, 125,000 miles, quit running, so he parked it 3 years prior. I put a new distributor cap on and drove it for 20,000 miles without ever draining the oil...but it burnt a quart every 50 miles. When I took the 425 apart to rebuild, all the valve seals were piled in the drainback holes in the corners of the cylinder heads. Most funnest thing ever: If I drove the car gently for about 20 miles, then kicked it down and ran it up hard, I could make a cloud of smoke that would stop traffic on both sides of a 4 lane highway. Very entertaining for a 19 year old.;<)
I just remembered that the TH400 would decide to puke a quart of fluid out the filler tube every now and then, pouring it all over the exhaust manifold. I presume there was a seal that was a bit hard in there someplace, but the trans always worked perfectly.
I also ruined the driving experience by installing a jobber cam when I rebuilt it. Before, it would pull hard to 5500, after it wheezed past 4000. A valuable lesson.