does installation of the cbperformance 30mm oil pump require machiing of the case to install in a ’74 1600 dual port.
There will not be a need to machine the case to install a 30mm pump. You will need to replace the 4 oil pump studs with longer ones. The easy way to do this is to take two 8mm nuts, install these on the stud you are removing, tighten the nuts against each other and turn the inside nut to unscrew the stud. Do the reverse to install the new longer pump stud.
Lastly there are 2 different cam gears for a VW 1600 style motor. One has 3 rivets and the other has 4 rivets. This is important, because each cam gear takes a different oil pump. Make sure that the oil pump you buy matches the cam gear you have in your motor.
Good luck, Andy