They have holes on both sides the Hughes bars are slotted at the top to bleed across the width of the rocker
Just noticed the groove should be in the bottom to allow the oil to spread across the roller i have them at the top wont affect oil pressure just the longevity of the rocker. Thanks always pays to check will rotate the bars will have to reset rocker clearance should be the same .
See Below
Rocker Shafts HUG1600 & HUG1620 Note the revised oil system on these new rocker shafts. The angled groove helps to spread the oil film on the lower side of the shaft and the lower side of the bore in the rocker. The pressure from the pushrods and valve springs are concentrated in this area so anything that encourages oil film is an improvement.
