OE lifters are a performance replacement for stock hydraulic roller lifters. Preload is meant to be setup similar to stock. Like stock, they are a ball valve style lifter.

OE-R lifters are specifically designed to perform at higher engine speeds. When engines are equipped with a hydraulic camshaft, high rpm is limited by the improper position of the internal piston as the lifter inevitably "pumps up". This improper location results in open valves and therefore leads to lost power. These lifters are almost required for any 3800 car shifting above 6000rpm because they help with the typical 5600rpm dip. OE-R lifters are preloaded and have to be installed between 3/8 and 3/4 turn (vs. 1/2 to 1.5 turns on stock lifters). These are a shim valved lifter like the ZZP and LS7 lifters. They have less range adjustment so preload is more difficult to setup. It's recommended to use a pushrod length checker.

We originally designed these for the vehicles we specialized in and have been using them for a few years now for the vehicles we deal with which uses the same lifters as the LS engines except in quantity 12 instead of 16, but about a year or two ago we have been dipping into the LS market with trunnion kits, valves, spark plug wires, coils, etc where we started selling these lifters to LS guys who have had nothing, but praise for them. So we decided to offer them on eBay. We have had many customers tell us they work very well on stock engines, mildly modified engines, and most of all highly modified valve trains. Like with all valve train modifications different length push rods maybe needed. Measuring with a push rod length checker is always recommended. Externally they look just like an LS7 lifter.