The F1 is not a staged combustion engine; it's a stock-issue gas generator -- as are the Merlin engines on the current generation of SpaceX rockets. SpaceX is

The F1 is not a staged combustion engine; it's a stock-issue gas generator -- as are the Merlin engines on the current generation of SpaceX rockets. SpaceX is working on a staged combustion engine (the Raptor) for their next generation of very-heavy-lift rockets, but plans for those are still in flux.