what are these helix's

[bluemonster1]

are these all stock helix's. 8BV70 ( is this one a stock 47 helix)

8BV50 overdrive

8BV71 overdrive

What are the last 2 helix's,what does the overdrive mean.Found these on e-bay.Don't know what angles they are,anyone know?

 

[Yama49601]

The 8BV70 and 8BV71 are 47's, the 8BV50 is a 45. Not sure about the overdrive part.

 

[change_up]

Yama49601 is right about the angles. Overdrive part is where they machine the helix to allow the secondary to open up more so that the primary can pull more belt in. Whether it works or not... I don't know and won't even try to comment on it.