I have a pair of these giant 431's in my 1964 46' Chris Craft Constellation or "Connie" as many refer to them as. They are huge and have tremendous power and sound. Squatting between a pair of these at about 3000 RPM's is intimidating but thrilling. They have never been rebuilt as far as I know. Port side starts and purrs like a kitten. Starboard cranks a little slower, runs just as well, very slight smoke at start and very light film on water after shut down. Average oil pressure on both is around 25 at 125*. Some of the changes on the 431 marine from the 430 auto, were the Carter crab, standard on almost all Chris Crafts, and dual point Mallory Distributor. The oil pan is oversized cast aluminum and each engine holds around 8.5 quarts SAE 30 oil. Most owners I know have moved to the Petronix electronic ignition for easier starting and done away with the points. Average running temp is 125*!!. They were introduced by Chris Craft as the "Thermocon Design" due to the low temp they ran at. Obviously another reason why they last forever. There are two water pumps and 2 separate cooling systems to each motor. I have heard there is some changes in the cam spec's but I have yet to confirm this. Gas mileage? Hah. not sure if you noticed what the gas mileage was on the test. At $4.00 plus per gallon on the lake lets just say it's a small fortune to fill er up. Thank goodness they run just fine on Unleaded Regular. Mention the 431 Lincoln motor to any marine mechanics today and they have no clue. Almost all the old boys that knew how to work on these giants have departed this world. A few are still around though.