Expert: Brad Sears - 11/29/2010

Question
QUESTION: I have a 1974 corvette did a little motor work to it. 5.7l  When i fire it up and it runs for about 5 min smoke comes out of the breather cap on the valve cover. Is this normal or is the oil getting burned up in the heads. They are brand new heads. Can you please help me start looking in the right direction to fix this problem.

ANSWER: The 1974 engine should have a PCV 9positive crankcase ventilation valve. This devise should capture this smoke and recycle it though the intake manifold. Do you have PCV hooked up? Let me know and we will go from there.
Brad

---------- FOLLOW-UP ----------

QUESTION: The PCV valve is on the driver side the side that is smoking has a breather cap on it. Should i put a PCV valve in that side also.  I have also just noticed that on the number 2 cylinder the intake rocker rock ever so little. The other rockers have a farther travel. Could this be a lifter problem.

Answer
Oh oh, sounds like maybe there is a camshaft lobe problem. If it was a lifter problem there should be a lifter tapping noise associated with it. The PCV sounds like the vacuum line running to the intake manifold could be plugged or internally collapsed. Also check the port in the intake manifold as these ports have been known to plug up. If the PCV feeds into the plate under the carburetor you might have to remove this plate to clean the passages. Once cleaned and the valve is getting good vacuum, then there should be no smoke coming from the breather cap.