I agree Jack,I thought you may be comparing the high arch with a mid arch from a different decade or comparing different makes,just making sure it all made sense without assuming what mowers you were referring to.
Yes catcher venting plays a big part in cutting efficiency,especially when people have blocked catcher vents.
As we were discussing Pope mowers I was thinking about the early Pope rotary valve, when the carby and exhaust changed sides I think it was because Pope wanted the thrust side of the piston to be on the cooler side of the barrel,just thinking under high load and operating temperatures the piston would wear less and the exhaust port is no longer on the pistons thrust side (piston has more support)
Victa changed the carby from one side to the other and then back to where they started, they went the wrong way on the Sheerline .It looks like Victa copied the early Pope that was wrong and I think when the thrust side of the piston is on the intake port side like the Victa Rotomo it has this operating temperature advantage for the piston.
