There are a bunch of timing gears from that time that are mismarked. It is necessary to count the teeth from the key slot to get the timing correct. It is covered in the May '28 Service News on page 30. The correct mark on the cam gear should be at the 15th tooth counter clockwise from the key slot. The crank gear is directly opposite the key slot between two teeth.
How Sweet the roar of a Chevy four!