What's the best way to clean aluminum heads? I am so use to clean cast iron so I was thinking of using a wire wheel w/ a dremel but i am afraid I will be taking aluminum off with the old gasket material. Should I go safe and use a scraper or is there a safe solvent to use?
When cleaning aluminum surfaces I use a softer brass wire brush, or even a stiff bristled plastic brush - they make both for the dremel. There's also a great rubber/plastic matrix pad they make for air grinders that's designed specifically to remove old gasket material without harming aluminum. They're the best I've seen. You can use any solvent you like - brake cleaner seems to work best; xylene if you have access to it. Keep it away from any rubber/plastic components (valve seals) if you can - no need to take a chance.
Like Michael said, softer bristles than the standard wire brush. On my performer RPM's I even 1500 grit sanded them after I got all the gasket material off. Then of course, I polished the outside of the heads, that took a lot of time.