1. Use a paint scraper or and coarse steel wool and remove everything caked on.
2. Take it to a self service car wash and and remove anything that will wash off.
3. Spray it down with easy-off oven cleaner.
4. Let it sit for 1 hr.
5. When the wife isn't looking!! put it in the dishwasher with lots of dish washer detergent on pots and pans cycle.
Repeat steps 3-5 until it is clean.
After you are done, cycle the dishwasher empty to clean out any residue you may have left.
You may have to remove the upper basket.
This procedure is fine for anything that will fit in the dishwasher.
I have used it for heads, bell housing, carb, engine sheet metal, and do not forget the 727 cleaning.