Set CAM with valve fully open

Had another discussion with Warren about an idea I had:

In stead of setting the timing using the tappet clearance procedure etc etc, which is very error prone due to the shape of the CAM lobe as its done on the very gentle beginning of the slope of the lobe, I decided to set the timing using ¬†the “top” of the lobe. That way I don’t need to worry about tappet clearance at all. All I need to know is the angle distance between the top of the exhaust and the top position of the mixture valve, and position that symmetrical around the TDC. I looked up my measurements and the spacing between exhaust fully open and mixture fully open¬†is exactly 240 degrees.

So all I need to do is set the CAM so that the exhaust valve “peeks” at 120 deg before TDC and the mixture valve peeks 120 deg after TDC

This new procedure popped into my head when I had another good look at the CAM. Here you can also see that the valve is only a short time at the top, so that’s perfect for using as a reference:



You can also see in this image below what I am trying to achieve:

To have the two valve movements overlap at the TDC (at about 40 deg in the image below), I will have to position the mixture valve top time at the TDC + 120 deg, or the exhaust valve top time at the TDC – 120 deg.



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