Mind boggling. Rockedyne used to have a dummy sitting out front of their San Fernando plant in the seventies.
Yes, they had big problems with combustion stability. They solved it by situating some copper baffles on the ejector plate. The article below has a great photo of those baffles. The Apollo Saturn V was a stunning achievement. It’s hard to imagine something as big as a US Navy destroyer being hurled into orbit (but only after stages 2 and 3 fired). Those F-1s burned for only 2&1/2 minutes and accelerated that mass from o - 6,000 mph (Over 7 times the speed of sound! I think it was on an Apollo flight that man attained his fastest speed relative to earth, almost 25,000 mph. That’s over 36,000 feet per second. Talk about being faster than a speeding bullet.
http://arstechnica.com/science/2013/04/how-nasa-brought-the-monstrous-f-1-moon-rocket-back-to-life/