i used a degreaser, kerosene, diesel, dish washer fluid and hot water to clean different parts experimentally to see which one does it best. Degreaser with kerosene firstly then dish washer and hot water do a good job.
For carbon build up on piston tops, i used a paint stripper.
After cleaning surfaces such as cylinder bores, head gasket surface etc. It is important to apply oil to prevent rust build up.
Engine and transmission after cleaning....