I have no experience with it, but I've heard horror stories about using oven cleaner on aluminum engines, something about it turns the engine a shade of white.
I've used automotive grade simple green combined with elbow grease and a bigass wheel brush with good results.
Also, electric parts cleaner (in an aerosol can) works well. Brake parts cleaner too, but that shit is crazy toxic. BTW: NEVER EVER EVER use Brake Parts cleaner on any part you will weld soon. The gasses, when heated by welding, can kill you instantly.