If you’ve never serviced the valvetrain of a GM LS-series engine, you’re likely in for a surprise when you remove the intake manifold and top engine cover plate, expecting to find the lifters and instead finding only a “bare” valley. The lifter bores (and lifters) are accessed through the top of the block in the upper area of the decks, requiring removal of the cylinder heads and cylinder head gaskets.
Let’s start by providing a bit of design background. The LS series of engines include both aluminum block (LS1, LS6, LS2, LS7, LS3, LS9) and cast iron versions (LQ4 and LQ9, primarily used in trucks and some SUVs). All LS-series engines feature roller-tip lifters, and all feature a 0.842-inch lifter body diameter. Instead of using “dogbones” or metal finger-trays to locate the roller lifters (to prevent lifter rotation in their bores), special LS-only composite plastic “lifter trays” are used.
These trays each hold four lifters. The cylinder block features large cavities above the cylinder bores for lifter and bucket placement. During assembly or disassembly, the lifters are held by the trays, allowing a complete set of four lifters and their tray to be installed or removed as a set (lifters and tray together).
Remember: Any roller lifter must not be allowed to rotate within the lifter bore, since the roller tip must remain in plane with the cam lobe. All roller lifter setups feature a method of keeping the lifters in register to prevent lifter body rotation. The LS engines simply use a different (plastic tray) retention approach. Flat surfaces on the lifters align within flat faced pockets in the lifter trays. This flat-to-flat engagement serves to keep lifters in plane with the cam lobes.
Bear in mind that, while the OE LS roller lifters are guided by these composite lifter “buckets,” there are a few aftermarket lifter arrangements that feature pairs of lifters that are “tie-bar” connected and do not use the OE four-lifter buckets. This is a modification performed by some engine builders. Considering the vehicles that your shop is likely to service, it’s unlikely that you’ll run into this. By-and-large, when servicing an LS engine, you’ll encounter the OE lifter system.
LS roller lifters may only be serviced (removed/installed) by first removing the cylinder heads and cylinder head gaskets. Removing the intake manifold and top engine cover plate is not necessary, since the lifters are not accessed within what you might consider as the “lifter valley” (as in previous generation smallblock Chevy engines). Lifter installation (with cylinder head and cylinder head gasket removed) will be the same regardless of your choice of OE or aftermarket lifters.
First soak the (clean) lifters in 5W30 engine oil for about 20 minutes. The lifters are then installed to the plastic lifter buckets. Simply orient the flats of each lifter body to the flats of the plastic bucket, and snap the lifter into the bucket. With four lifters attached to the plastic bucket, you can then ease the four-lifter bucket assembly into place, inserting the lifters as a group into their respective bores.
The lifter bucket is then secured to the block with a single 6mm bolt, which is tightened to 125 in.-lbs. (I prefer placing a drop of medium-strength thread locker onto the bolt threads). Once the lifter bucket is secured, you can then use a pushrod to gently push each lifter down for cam lobe contact. As you push down each lifter, you will hear and feel a slight “snap” as the lifter disengages from the lifter bucket’s detent and makes contact with the camshaft lobe. The lifter flats remain engaged in the buckets for proper lifter orientation (preventing lifter rotation). Remember: A flat tappet setup requires that the lifters be allowed to freely rotate within the lifter bores, whereas a roller lifter’s body cannot be allowed to rotate, since the roller tip must remain in a fixed plane relative to the cam lobe. That’s why all roller lifter-equipped engines will feature some sort of method to prevent lifter rotation.