Something that rebuilders of vintage Honda engines know to do is, as often as is possible, replace the cam chain. This is just as necessary with the later Hy-Vo cam chains as it is with the older roller type. In fact, with the added abuse they get, the Hy-Vo type probably wear even faster. Fortunately, with so many of these engines needing top end rebuilding long before they require bottom end work, it is not difficult to separate and replace the cam chains. Even the Hy-Vo types have been done this way for as long as they have existed.

A worn cam chain produces retarded cam timing. This delays valve timing and alters the engine's compression phase, with the result reduced power and responsiveness. You don't even need a degree wheel to spot this. The factory timing marks plainly communicate the timing aberration. Of course, the factory cam chains for fifty-plus year old Honda engines are becoming scarce. But it's worth the trouble.

It's also true that a degree wheel will pick up another reason for intake open timing at 0 BTDC or less. Cam wear. 1970s Honda cams wear pretty steadily. It is not unusual to see the lobes 0.020" or more worn off before 15,000 miles. Between the two then--the cam chain and the cam--these old Hondas can be be perked up considerably with a little careful degreeing.