No, vapor blasting is not dangerous to engines. In fact, it is an improvement. The only problem is they are hard to find. This place has a 5 star rating by me, and they will even help with the shipping. Read the facts:https://www.restocycle.com/vapor-blasting-faq
KC, From the FAQ of your link:
How to you prevent blast media from becoming trapped in my parts?
With regard to blast media, the first order of business is to start with a clean part, including in the oil passages and galleries, which are very thoroughly cleaned. Oil and other engine passages are then plugged or masked. Any part with a thread is also plugged to prevent media from lodging in the threads. After vapor blasting parts are immediately rinsed, several times, and then dried with compressed air. Then the plugs and masking are removed and the process is repeated. It is however the customer's responsibility to verify that no blast media is present and the parts are ready to be put back into service.
Nowhere that I can see does it say that your parts will be blast-media free.
For my money, i will continue to avoid.