I looked at the valve you are talking about on ebay. My ford followers and I always called these a vacuum check valve. On page 82 of the Haynes Ford Mustang ii (owners workshop manual) it talks about this valve. It says that a spark delay valve is incorperated in the system to delay spark vacuum to the distributor diaphragm unit for a predetermined time. There is a vacuum diagram on page 81 that shows a SDV valve. It is just like a vacuum check valve. There is alot of information in this book that is very helpful.