stock rocker arm questions

[Spooled231]

Guys,

Ponder on this and let me know what you think.

My dad and I both have replaced the original factory rocker shafts and arms that came from the factory when we did some upgrades a few years ago with brand new GM rocker arms and shafts. The original set of rocker arms are not labeled and the push rod oil passage is dead middle center through the rocker arms.

Now,

I didnt notice this until I went to the dealership to get another set of factory rocker arms the other day. They tell me that there is a Left and Right side. I checked my GM Parts book, yep, Left is 1241851 and right is 1241850. I was kinda curious in what the difference is in the 2 rocker arms were if there was any. I put them side by side and found that the rocker arm stamped "L" has the push rod oil passage on the right center. The rocker arm stamped "R" has the push rod oil passage on the left center.

Tonight I proceeded to pull off the valve covers to pull the rocker shafts and arms off and found that the set we bought a few years ago are labeled "L" "R" "L" "R" "L" "R" on both driver and passenger sides.

Can someone explain to me why the design change in the rocker arms having the push rod oil passages in 2 different locations and how come "L" and "R" are combined together and not all "L" on driver side and all "R" on passenger side?

Thanks
John Martin
86 Buick T-type
1.533 60ft
6.93 @ 100.1
10.91 @ 123.6

 

[Rob_85Ttype]

There are supposed to be two types, L and R. Alot of the aftermarket ones, and even the factory ones were made sloppy, so the hole and pushrod dimple were punched in or near the center rather than offset to one side. To truely get a left or right offset, I had to look through several of them to get the ones I wanted. Without the offset, my pushrods were very close to rubbing the sides of the holes through the heads. The L and R are for left and right hand side of the piston.