http://www.hotrod.com/how-to/engine/pon-0509-1973-emissions-control-systems/ http://www.hotrod.com/how-to/engine/pon-0509-1973-emissions-... Here's an example

http://www.hotrod.com/how-to/engine/pon-0509-1973-emissions-control-systems/ http://www.hotrod.com/how-to/engine/pon-0509-1973-emissions-... Here's an example from the 70's