340 Cam


"Those are gross duration figures, not duration at .050."

Yes they are. Correct

Like I mentioned earlier, back in the 60's @ .050 specs weren't used. Any @ .050 specs are purely speculation unless a factory cam was found and measured. @krazykuda has worked on that project. May be he will chime in. I can see where advertised duration numbers can be big. Duration is the amount of time in degrees the valve is open. If you start measuring it at 0 or close to zero lift of course the numbers will be higher than at .050.