The Cessna 170 with the C145-2/O-300-A engine developed 145HP at 2700RPM from a engine with 301 inch³ displacement using 7:1 compression cylinders. When you crunch the numbers this little engine pushed out 3.9192 ft³ of exhaust every second out the 6 exhaust ports having a area of 9.63 inch². The L-19 with is O-470-11 Continental engine delivered 190HP at 2300RPM from a engine with 471 inch³ displacement. This engine put out 133% the exhaust that the C145-2/O-300-A out through the exact same sized cylinder flanges, riser pipes, exhaust mufflers, and tailpipes. By the time the O-470-A was installed in the Cessna 180, 151% of the exhaust that the original flanges had going through them started creating problems with the flanges deteriorating and warping. The solution was to use a 4-bolt flange starting with the O-470-K.