The only mark I'm aware of is on the front surface of the flywheel and is accessed by small cover adjacent to the oil filter. An alternative method to find TDC on #1 (and to verify that your flywheel is correctly mounted) is to remove the valve cover, rotate the crank in the normal direction of rotation, look for the #1 valves to be rocking, then advance another 360 degrees (at which point #4's valve are rocking I think). If you find the point at which #1 is rocking, then look through the sight hole for the markings. You may need to wipe crud off the flywheel. If you clean it and apply a paint pen to the marks, it'll be easier to find again