Oil burn cloud on engine deceleration

Those type crossover blockers are sketchy for sure. Tried that on a BB once and did not work well! Always had some oil seepage that either went in the valley or got pulled into the center bores.

First thing is you started with two breathers only yes, and the blocker(s)? It does not take long for positive pressure to start pushing gaskets, the longer they cure it may lengthen that. PCV helps from the start! It does more than just evacuate unwanted blow by and such and keeps that positive pressure from doing the damage.

They make gaskets specifically to do the crossover block don't they? I Seem to remember installing gaskets of that type on my brothers 340 back in the late 80's that were blocked in the design. My BB blockers are built into the valley pan (no holes)!