That's exactly right , if you was to up the comp. ratio & had a stock cam in this engine , take a comp. reading ., then install a bigger camshaft , then take a comp. reading & you will see what we are talking about. That's why it is BETTER to up the comp. when installing a bigger cam profile . The bigger the camshaft the more comp. that is needed to let the camshaft perform as it was desighned to, unless you are building a turbo engine then there are different profiles for turbo engines all together.
One of the most important things to remember about going to a bigger cam profile is when the valves are opened more & longer , higher compression is needed,unless you are turboing the engine .So if you are going with a bigger cam then you need to up the compression too to make the cam work like it was ground to do.
It doesn't matter what I need , every time I go to the parts store to get anything for a DATSUN they never have it in stock . they alway's have to order it .