These heads had incorrectly-ground exhaust seats. Somebody ground them way off. You could see huge amounts of light between the valve and the seat. It's like they ground them without locating a pilot in the guide, or . . . who knows? The motor had no compression, it was all leaking out the exhaust seats. We had our buddy Radar machine out the old exhaust seat, and press in new steel seats - and now they're perfect !
Noot cut new seats, ground the valves, lapped 'em in . . . nice set of heads again.