Got the GTO running after swapping out the 455 with a 428. Took for about a mile ride and when I got back I noticed smoke coming from the breather. Let it sit for a couple days and took it around the development which is a shorter ride and no smoke. Sat a couple days and went the same route as the first time, about a mile, and it’s smoking again. Did some research and sounds like it’s blow-by from a bad PCV valve, or worn rings. I shook the PCV valve and it rattles. From what I’ve read that’s good. My question is, is there another way to tell if the PCV valve is good or bad other then rattling? Are there better PCV valves then others? Not sure what brand mine is. Lastly, is there anything else besides the PCV valve or worn rings that could be causing this? Guy I bought the engine from said it was rebuilt recently with very low mileage. Said less then 3000. I kind of question that but it does look fairly new. Had him run it on his stand for about 20-30 minuets without any issues. It’s a 68 block rebuilt to stock he said.