Cam to cam tunnel clearance

Searching provided no clear answer to this, but I'm wondering what the consensus is on cam to cam tunnel clearance? I'm installing a webcam 312A grind, and the tunnels need to be bored out some.

Thanks

i installed a 312 cam (from Jim Comstock) and the cam bearing od was about 0.005" undersize requiring new cam bushings be installed.

Since Web cams are welded and reground on returned cores (for the Norton ) i would have thought they would reface the bearing dia. to a common size...