I got distracted into watching some of the radial engines mounted on trailers for folks to watch, and I have seen a few at gas engine shows.
The big radial engines seem tough to get running, and they never want to run on all the cylinders.....I wondered why?
The more I thought about it, I considered that the engines were made to swing huge propellers at relatively low rpm without gear reduction (to keep the propeller tips from going supersonic)....so they had to make a lot of torque and HP at low rpm. Once up to speed and under power the engines ran great - but these "show" engines have cut down propellers that offer very little resistance and only move enough air to cool the engine - most likely the throttle for the engine is barely open and these huge engines are not operating where they are designed to run well.
They are still really cool to watch! The Spruce Goose has 4 radial engines on each wing, each one making 3,000 HP, 4 rows of 7 cylinders makes for a total of 28!
https://www.youtube.com/watch?v=zBMsdXGOm5A