Quote:
I didn't think it was possible to have valve timing with no overlap; when my VW was on the street, the accepted wisdom was that it was almost essential to have some overlap in the works. With the air-cooled engines, the overlap actually helps cool the exhaust valve by letting some of the incoming charge flow over it, and also helps pull more charge into the cylinder. Kind of like having to open the door and an opposing window in an apartment to get a draft going.
I`m sure your mild old VeeDubya cam had both valves shifting a whole lot more air than these 865 Speedies, remember 1mm open 7 degrees underlap! My lawnmower valves have more overlap - honest. And yes you are correct to mention the relationship between inlet and exhaust flow, the mediocre opening of these std cams almost entirely eliminates any benefits there may be available though.
Cheers
| 
