Dizzy shaft grooves

[CobraSix]

So, I was tearing apart a loadomatic and DS2 dizzy and noticed the groves spiralling down the shaft to the vicinity of the cam shaft gear. They terminate about have way down the camshaft gear, on the inside.

My guess is that these grooves are to help oil flow around the dizzy gear?

If so, was looking at the DUI and noticed they don't have the grooves. Are the grooves necessary then?

I'll try to post some pictures later

 

[MustangSix]

Common on a lot of vintage machinery to control oil by acting as a seal.

 

[Emerald 74 4X4]

My distributor in my 74 had those as well. I am pretty sure it was an original distributor as it used to have points. They changed to electronic in 75. Now it's just an oil pump drive.