I'm building a home brew "cam doctor" which can be used on an engine installed in an air cooled 911. It will require removing one intake rocker, and will enter lift data for both lobes every 5 (or so) degrees of cam rotation, which will be measured by a rotary encoder on the fan belt or directly on the crank pulley as the crank is rotated 720 degrees. A microprocessor should be programmable to send a "data" signal every 10 crank degrees to the two dial indicators It will measure lift at the cam lobe, not lift at the valve.
It requires two data output capable digital dial indicators (the cost of these has plummeted, and in intermediate encoder to produce CSV output to an Excel spread sheet is now also reasonable in cost, in contradistinction to the most common high end similar measuring devices). Sort of by mistake I purchased one with a half inch travel (the other two I already owned had an inch of travel).
I was thinking of max lift being about 12.5mm, but then started worrying I wouldn't have enough travel. Then I tried reassuring myself that lift normally is specified at the valve, where cam lobe lift is magnified by around 1.3-1.4X, so half an inch ought to be plenty.
Am I right about this?
The mockup is for the Mark 1 version, which easily accesses the exhaust lobe on its backside with no rocker in the way, but because of the attachment on the backside of the indicator prevented them from being placed on the same lobe pair - not a big deal as the spread sheet could compensate. But the intake it reached only shows a tiny sliver outside of the rocker. I thought a narrow indicator tip could use this, but on trying one saw that the angles involved would bend the tip (there is a reason lifters have a relatively large diameter in engines which use them, I guess). So plan B calls for pulling an intake rocker, which is not a big deal. And the dial indicators I am using come with a back without the attachment part.
But my question is about cam lift - the rest is background.