Back in the late eighties/early nineties, the company I worked for had been operating DC-6's (R2800) for many years. We got into the DC-8's at that time, 54's and 55's. Get this! WE had better engine reliability on our DC-6's than we did our DC-8's. I happened to be dual qualified as an engineer at the time, and I never would have believed it had I not seen it!
Our company was contracted to go to Miami and do the island grocery run for Trans Air Link. They were having an exceptionally hard time completeing the 6 leg roundtrip back to miami with four motors running. Well, we managed to complete the 6 week contract without shutting one down.
Engine reliability had a lot to do with how the engineers treated the engines.
Hell yes, big radials were reliable!
I have some friends that flew skydivers in the Southern Cross DC-3 in Z-hills, and it had Wright 1820's on it. they managed to do very well with their engines. Again, it had sooo much to do with how they were treated!