I received the firewall forward kit drawings from Van's today and decided to install the heater bypass valve in the firewall. I purchased the stainless steel heater bypass valve from Plane Innovations. Reviewing both OP-29 and the instructions from Plane Innovations, I measured and marked the location for the 01.95 inch hole that I would have to make in the firewall. Reviewing some ideas from other RV builders, I decided to use my fly cutter and a hand held electric drill. First I drilled a pilot hole and increased it to 1/4". I clamped a piece of would to the firewall and used a 2x4 to brace the firewall against the wing spar. Using Boeing Lube, I started cutting the hole at a slow speed. I stopped several times to lube the cutter and also sharpen it. Ten to fifteen minutes of cutting and I had a hole. Deburred and clamped the heater bypass valve in postion to mark the two bolt hole. I drilled those out to #12. I temporarily installed the valve with AN3 bolts until my SS bolts arrive.
