First of all, you cannot use anything that is caustic like oven cleaner, automatic dishwasher detergent, concrete floor cleaner. The 'Easy off' oven cleaner will instantly turn your engine black. You can never make it right again.

Common solvents used are carb cleaners and brake cleaners.

The talk of the town is antifreeze in a potpourri's pot or crock pot.

Don't boil it or it will turn the engine dark. Just heat it up to a point just below boiling and let it soak 12-24 hrs. Then use a brush like a tooth brush on it.

Take the head and back plate off. Remove the carb and do separate.

You can never cook food in the crock pot again. It will be poisoned by the antifreeze.

Good luck,

Jim