Expert: Brad Sears - 2/10/2010

Question
Our newly purchased Convertible 63 Fairlane with the 390 is smoking from the oil filler tube. It has "Thunderbird" labeled valve covers without a PCV anywhere?? are we missing the PCV valve, and do we need it?? Smoke will seep out of the hood when stopped, ect. Thanks in advance for all your help, Marshall in Portland

Answer
There should have been a PCV system on the car from the factory. But that is not my main concern here. The engine should have very little smoke coming from the oil fill cap especially at idle. The presence of the oil smoke leads me to believe that you are begining to see a problem in the engine where engine compression and combustion are bypassing the piston rings and getting in to the crankcase vaporizing engine oil and causing the smoke. My first step would be to do a compression test both wet and dry. Warm up the engine and remove the plugs. Install a compression gage in each spark plug hole, one at a time. Then crank the engine over using the starter for 4 compression stokes. You will hear the stokes or you can count the strokes on the compression gage needle. Record the reading and go on to the next cylinder. After testing all eight go back to the first cylinder and pour about a teaspoon of oil into the cylinder and repeat the compression test on that cylinder. Record the reading next to the first reading and test the remaining cylinders. Now here is what you should see on a good engine. The reading should be between 125 and 150 on that engine. All cylinders should be within 25% of each other. And the wet test should not be significantly higher than the dry (first) test. Uneven compression indicates a weak cylinder. Low compression on all cylinders could be piston rings or a  loose timing chain. And a difference between dry and wet test indicates weak or worn piston rings.
Brad