I’m impressed with how the results look. Very cool. Lots of ideas coming to mind. Wish you were next door.
With valve cover, the inner shield will trap any particulate and it will be washed out during operation into your engine.
I would NOT want any abrasive of any sort to be rinsed into my engine after cleaning.
The cleaning looks great and I can see the old cars enthusiasts using your services to restore old parts to new looking condition.
You may want to consider further cleaning on the valve cover if you haven't already.
Really cool. Is there a coat of paint on that or does it clean up like that?