Any pair of gears, helical, spur, miter etc. will rotate in opposite
directions. You cannot change the direction of rotation by changing the
hand of the helix. Additionally, on intersecting shaft applications only
helical gears of the same hand will mesh. The only consideration when
selecting the hand of the pair is the direction of the resultant thrust
which, in this case, must be toward the distributor housing.

If you check a power transmission catalog, such as Browning, they will show
diagrams to explain this.
"Gudmundur" wrote in message
...
In article ,
says...

I have twin 350 Chevy inboards with the port standard rotation and the
starboard reverse rotation. The port has a standard timing chain while
the


If the crank and cam turn backwards, the reverse cut helix causes the
distributor and oil pump to turn in the 'normal' direction. Two reverses
equal a forward, much as 3 lefts equal a right.