easy way to see what is going on. oil can be seeping up through the gasket and down the runner into the cylinder, but the constant flow of gas washes the runner relatively clean, so it's hard to tell if any oil is getting by or not.

put some dye in the oil, the kind that is meant to check for leaks. pull a carburetor and look down into a port with a black light, and if you see any of that glow, then oil is getting through.

kind of tough to get your head and the light at the right angle, but the dye responds well to the black light, so you will be able to see it.