I had this engine rebuilt 4 years ago and a few months ago I finished the 65 Ranchero it is in. After I had the exhaust done and was ready to start driving it. It started smoking really bad. I pulled the head off and there was a lot of oil in the cylinders and behind the intake valves. I took the head to a machine shop to have it checked out. I was told there was nothing wrong with it. But being it was off, I ordered stainless steel valves and new teflon valve seals from FSP and had the shop cc the head and do a 3 angle grind. The machinist told me that I had other problems. So I ordered a set of piston rings from FSP. I pulled the pan and replaced the rings. The old rings looked OK and the gap was correct. The only difference I notice was the oil seal rings didn't seem to have the quality of the new ones. I put it all back together and no more smoke. I had some problems with the Autolite 350 cfm carb, so I bought a new Holley 350 cfm carb and with a few tuning adjustments the car was running good. I was quite pleased with it. Yesterday it started smoking again, but only out of the left ehaust pipe. I have driven it 200 miles with no problem and now this again. I pulled the spark plugs and all except #5 had the perfect match to the picture in the manual for the perfect burn condition. #5 was oil soaked and with my finger I could feel oil on top of the piston. Does any one have any ideas or is this just a lemon engine. I am at the point to give up. I can't drive the car because the smoke increases with engine RPM increase. At about 2500 RPM's it is like laying down a smoke screen and driving it home yesterday I had people flipping me off and yelling to get it off the road. I have about $3,000.00 in this motor and I just don't feel like dumping any more time or money into it. Any opinions or ideas of what I am doing wrong?