These engines did not have positive valve guide seals and the guide top must be machined to accept the good ones.They are a MUST for oil control on the SBC.You can almost never get over 1200 miles per quart without the seals. Blowing oil out the draft tube: does it have the oil separator installed under the manifold? Is the crankcase vented up top near like original? It is important to allow air in here instead of the draft tube. Observation: PCV really was better when done right, even though we thought differently when it first showed up (1963 in Tennessee).Look at the piston tops, if the rings are passing oil we usually see the carbon on the crown washed away around the edges.If the guides are at fault look for excessive oil in the inlet and exhaust passages or on the valve stem/head.Yes the exhaust needs the seals also, just not as bad as the inlet.
