I attended the 60th Anniversary Open House at Johnson Space Center - NASA - on Saturday morning.
These are F-1 engines on a Saturn V rocket. Item #40 for the October Scavenger Hunt - Educational.

The F-1 is a gas-generator cycle rocket engine developed in the United States by Rocketdyne in the late 1950s and used in the Saturn V rocket
in the 1960s and early 1970s. Five F-1 engines were used in the S-IC first stage of each Saturn V, which served as the main launch vehicle of the Apollo program.