[Old H2S]

Yes, I did have to scrape the corners.. I use a bamboo chopstick, my point is that once I broke through the crud and this stuff got underneath it worked fast lifting and liquifying the old oil. This sure beats a toothbrush and a can of Brakleen.
I got a lot of tools for cleaning parts up to bead blasters and ultrasonics but they work from the top surface of crud inward and once I gave this stuff some bite to get underneath it was quick. It does not smell much and it did not tear up my hands or arms when I got splashed. It sprays on thick and says do not dilute so dumping it in the ultrasonic might not work. I took the picture because of how shiny the inside of the block came out, the outside still looks rough after 40 years so it will not shine up aluminum but it is not bad if the surface is good to begin with. I would not let it dry on the surface ether, could be a ***** to get off and as wheel cleaner??? who knows. I just found it and will see what problems and attributes crop up.