With a cam as mild as a stock stovebolt engine has, the exhaust valve actually gets completely closed before the intake starts to move. On #1 and #6, the UC mark will get past the pointer before you see any movement on the intake rocker. On engines with very radical racing cams, the only way to get a good adjustment is to find the split overlap point and then adjust the cylinder halfway around the firing order. Fortunately, you've got almost the entire power stroke to work with before the clearance on the stovebolt exhaust valve begins to close up. so there's a huge margin of error before there would be an incorrect adjustment induced by missing the mark a little. The main advantage to companion cylinder adjustment is that it works on any engine with an even number of cylinders, with solid or hydraulic lifters. On odd-numbered engines like an Audi 5 cylinder or maybe a GEO Metro 3 cylinder, just find the rocking point, then turn the crankshaft one more turn and adjust!
Jerry
