Cutting door in foundation block wall

I have a home that has a large crawlspace. I have enough headroom, twelve blocks high, to install a standard height 36" door and it would involve cutting through an 8" cement block wall.
It was originally an outside wall with one story above before the addition of a storage room.
Would it be advised to support the above structure before removing blocks, and would a lintel be necessary?

I would be wise to contract a professional contractor to do this. You are messing with the structural integrity of the building.

doorway

You would only need a lintel if there were block or brick above the opening, and it does not appear that you would have room for that. You could need a header, but depending on where you cut the door relative to the framing members above it, there might be little, if any, need for it.