Need some help. Just removed the heads off my 350. I got alot of tiny dirt chunks in it. How do I clean it out and can I do this with the valves in it or do I have to remove the valve springs?

What are your plans with the heads? Just clean them and put them back on? You can use oven cleaner, it's one of few cleaners strong enough.
If you're disassembling the heads for machine work, just hot tank it.