Ed,

I measured a WACO (don't remember the model) several years ago, and it had no right or down thrust built into the mount, or the firewall, for the 224 Jacobs radial. I guess that it all depends on what you are talking about. I do know that some of the commercial jets do have some down thrust built in. I have also measured several opposed 4 and 6 clyinder applications on general avaition aircraft, and found neither right, nor down thrust evident either, thus my initial statement. I know that for years, we have used it in our models, especially those used for pattern, and F-3a. But was that not used to keep the plane's heading more automatic?

Bill, AMA 4720
WACO Brotherhood #1