I see above the B-29 was finally re-engined with the P&W R-4360, same engine that went into the Boeing Stratocruiser. This had issues of it's own, among them a propensity of the props to shed blades in the cruise, especially mid-ocean (possibly an issue of how much power they had to handle).
The R-4360 was a 28-cylinder (7-cyl x 4 rows). On a 4-engined aircraft that's 224 sparking plugs, what chance all would be working 100% in the mag check ? It also suffered from having 4 rows of cylinders, the back row were just too shielded by those in front and would overheat. The Big Ends on the crankshaft must have been a fitter's delight as well !