51fixer wrote:
I don't know the G series but other series of Allisons have several features that make an opposite rotating engine faily easy to produce.
The crank features the same flange on both ends of the crank. To rotate the opposite direction you flip the crank around.
Many parts are the same for both directions. Some are specific to the each direction, among those are the prop gov, starter and ignition parts. Other accessories rotate the same direction for both engines. There is a gear arrangement to rotate the accessory drives the same direction even though the engines rotate different directions.
If the G series follow this same design then the opposite turning engines aren't that much trouble to produce.
Allison Competition Engines has been stating that they've had four G6 motors for this project since 2003. As Rich said, I don't believe the motors are an issue.
http://www.aceallisons.com/pdf/200405.pdfhttp://www.aceallisons.com/