Bricks, Masonry, Asphalt and Concrete - Cut larger door in concrete block wall

I'm removing a door in a concrete block wall and replacing it with a larger door. I need to remove about a foot of the concrete block for the new door.
Should I cut it out with some type of saw or grinder , or should I chisel it out? Thanks

Go to a rent a center, and ask them to rent you the proper saw, gas powered diamond blade, and with an attachment to add water to blade to keep down dust. A hammer and cisel is a crude way of doing this and you may weaken the structure, and you rough in wood, would be hard to fit against a chiseled edge.

If there are block, presently over top the opening, and you make the door wider, make sure that what ever is holding those block in place, will still be there after you cut your hole bigger. You may have to re-do the support over the door unless there is nothing over it now, in which case, you shold be OK

Before going to the rental center, get some estmates for having this done. The blades are expensive. Break one and you more than paid to have it done. And, yes, the chance for breaking a blade is pretty good for a diyer with little or no experience.

You may find the cost of having it done to be worth it rather than prohibitive.

And do take care with the header. You will almost certainly have to do something with the header.