400 pontiac motor rebuilt at a machine shop. Put it in storage for the hurricane from 9/9/17 to 11/25/17. Tried to start it and pow... dropped valve. Builder said 2 tanks of avgas 6 months before storage dried out the valves. no warranty $4000 to fix it. When did fuel start lubricating valve stems?

 

http://www.fuelexpert.co.za/canirunavgas.php