It isn't unusual for big stroker motors to have a lot of crankcase pressure. Even if the rings have sealed up the bottoms of the pistons are pumping a lot more air in a stroker than they did in a stock engine.

One the dyno I usually use large #12 AN breathers on each valve cover. If the oil pan is restrictive then the air doesn't have anywhere to go and it builds up pressure. Pushing out the dipstick is a sure sign of a lot of crankcase pressure.

You can measure the blow by with the engine running just to see how much you have. You can also do a leak down test and a compression test if you think the rings haven't sealed up.