Some time ago I had what turned out to be bad valve guides in my 289. The engine would consume
oil in a cruise mode but it wasn't visable or apperant at idle and it was still crispwith sharp response . I could not figure out were the
oil was going until I pulled the heads. About the same time the
oil pressure had become intermitantly irradic above 3000 RPM. After checking and veifying the oil level as correct it would be fine but after about 100 miles (on a cruise) it would begin to waver between 40-55#
and it usually runs at 70-75#. I eventually pulled the pan and found a minute crack in the foot of the oil pump pickup tube assembly. What was happening was that the oil level would get to a point where the combination of windage, suspended oil and oil in the top end would all reduce the level in the pan and uncover this crack causing it to suck air in the system (not good).
I have since fabricated a nice brace for the pickup tube made of 1/8x1" in an "L" shape. I heliarced it to the tube a have a captive nut in the windage tray that it screws into, it is quite solid and helps dampen any harmonics that may be present and provide alot of additional support for the pickup itself. Anything you can do aid in oil drainback is to your advantage. The drainback holes in the ends of the head that provide a path for the oil to return to the pan geneally do not align very well with the block and there are several sharp edges that can be eliminated. It all helps. As said earlier keep the pickup about 3/8" inch off the pan bottom.
Good luck
Rick
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