Port orientation

RknRusty wrote:

TheotherGeoff wrote:It seems that most all Cox 1/2A engines have the ports at the 10:00-4:00 position instead of at the 3:00-9:00 position that would seem most logical for good power. One bypass port is blocked by the crankcase; the other is blocked by the reed housing. Wouldn't they go better with the exhausts at 12:00-6:00 and the bypasses at 3:00-9:00?

Curious Geoff

It would seem so. To have the bypass ports equidistant from the reed at 3:00 and 9:00 seems like they would get the most even distribution of fuel. I have gone to the trouble of putting the crankcase shoulder on 1000 grit paper and knocking a quarter of a thread off to get them to align that way and have never actually seen any difference. It doesn't seem to matter.

RknRusty wrote:No, the distance is not that much different, barely measurable just to knock off a quarter of a thread's depth. The engines probably varied that much from the factory or else the ports would all be aligned the same anyway.

pkrankow wrote:The threads were not indexed during manufacture, so the alignment is purely random. The Special .17 MKII is the only cox engine that the threads were timed on so the ports line up in the same place on every engine.

Phil

cribbs74 wrote:

pkrankow wrote:The threads were not indexed during manufacture, so the alignment is purely random. The Special .17 MKII is the only cox engine that the threads were timed on so the ports line up in the same place on every engine.

Phil

Correct, except I assume you meant .15