[wdnavion]

Yes JohnD, we have a 49 Navion which I can't afford to fly just now but it is a wonderful machine.
As to "getting out of time", it is not a big problem. You remove the plug from the alternator side of the engine case and bump the machine in high gear until the "T" mark on the alternator rotor inside lines up in the center of the plug hole. It should have a dab of gray paint from the factory to make it easier to find. Just make sure that you have the rotor in that position when you re-install the camshaft in the head. Make sure that you have the punch mark with the white paint on the camshaft pointing aft and aligned with the parting surface for the valve cover. You do want to make sure that both valves are closed when you remove the valve cover. The difficult part of the job is that there is just barely enough room to get the valve cover on and off the head since it is so close to the frame tube under the fuel tank. Also, in order to get the chain off the sprocket to remove the head, you have to take the two bolts off and remove the sprocket and then the camshaft. It is fun being careful to not drop the bolts and the keeper retainer from falling down into the crankcase where they might be hard to retrieve even with a magnet. Also use tywraps as in the pictures to keep the chain from falling down into the crankcase. It took me about 5 hours from start to finish including inserting the helicoil. The instructions in the factory manual found on this web site was pretty thorough.