Thanks for all the help. Checked Van's, no joy. We decided to make our own valve, a manually acivated door in the top of the airbox piano hinged at the bottom. Pulling the control knob will swing a rocker arm pushing the door down and open & pushing the knob in will pull it closed against the inside...

We are building an RV8A, IO-360, and in the process of installing the airscoop on the bottom of the cowl, the airbox & filter. I am looking for a BYPASS VALVE to install on the top of the airbox to allow alternate air in the event of freezing or some other clogging of the air intake. Any help is muc...