Brief Description: Drill Mounting Holes for Cabin Heat Valve
I marked the centerline for the cabin heat valve on the firewall, installed the recess and checked the position of the mounting holes. Marked the position of the first hole with a scribe and some marker for contrast. Centerpunch and the drill with #40 through the firewall with wood block backup, then upsize hole with a unibit for mounting bolt. Put in one bolt then marked second hole and drilled the same way. Test fit the valve and the bolts worked well.
