I have built many flatmotors over a 55 year period.This particular block is 39 truck(3 3/16 bore with .090 overbore.) This block puts out so much oil misting that the vent tube in the pan(front passenger side) blows oil constantly and I don't know why.The end gap on the rings was checked,new bearings(good oil pressure 40-50 hot at 2500 rpm.) the crankshaft slinger is in place and run a standard fuel pump with umbrella on push rod.Run big intake valves with MCF camshaft.370 lift,Weiand cheater heads,Edelbrock slingshot intake.headers.nissan perf stainless mufflers(glass packs)All mounted in a 32 cabriolet Henry highboy roadster.Compression gauge reads about 140 all cylinders.Engine does not smoke nor foul plugs(have 43 main jets in 97carbs-runs good just "blows oil constantly out the vent tube" and not much fun to drive. Any suggestions are appreciated;don't know what else to check or modify. Breather on top of fuel pump has no limitingobstructions and vents well to atmosphere. Thanks flatheadjohn47 Texas 979-595-7324 cell.