A regular mineral spirits washer for small stuff. A homemade "Hot tank" for blocks&heads. A "repair drum" which is a large 55 gal. type drum. It sets on a stand on end. I welded a threaded bung from an old hot water heater in the lower part. Installed a large electric heater element and the thermostat from the old water heater. Made up a metal tray/platform that fits well above the element to set blocks/heads on.
I then added circulation to it by buying an old soft drink Carbonator pump. )Goodwill store, $10.00) Mounted to the side and plumbed into home made jets that are bunged into the side. When turned on it makes a really strong whirlpool.
For aluminum I usually use hot "Super Clean" but you have to be quick, as the cleaner can be hard on non ferrous parts. For blocks and heads (iron) I use a cleaner made for metal. It smells like oven cleaner, has a high Lye soap content.