Tech Stuff

Hands-on with GM LS roller lifters

The GM LS engine versions (LS1, LS6, LS2, LS7, LS3, LS9 and the iron-block cousins) feature roller lifters that are guided within plastic lifter “buckets” that are located in cylinder head deck cavities, as opposed to being located in the lifter valley on earlier V8 engine designs. The intake manifold or top engine cover plays no part in lifter access. All LS engines feature roller camshafts and roller lifters.
<p>The GM LS engine versions (LS1, LS6, LS2, LS7, LS3, LS9 and the iron-block cousins) feature roller lifters that are guided within plastic lifter “buckets” that are located in cylinder head deck cavities, as opposed to being located in the lifter valley on earlier V8 engine designs. The intake manifold or top engine cover plays no part in lifter access. All LS engines feature roller camshafts and roller lifters.</p>

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.

Don’t assume that the intake manifold and upper engine cover plate must be removed in order to access the lifters. The top plate merely covers the valley.
<p>Don’t assume that the intake manifold and upper engine cover plate must be removed in order to access the lifters. The top plate merely covers the valley.</p>

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.

With the top cover plate removed, the valley may feature simply an oil drainback area, or may (in the case of a DOD, or displacement-on-demand system) feature a series of oil bleed-off bosses, with solenoids that prevent lifter pump-up to deactivate select cylinders. The lifters cannot be accessed via the valley, so if your task is to service the lifters, don’t bother to remove this top cover.
<p>With the top cover plate removed, the valley may feature simply an oil drainback area, or may (in the case of a DOD, or displacement-on-demand system) feature a series of oil bleed-off bosses, with solenoids that prevent lifter pump-up to deactivate select cylinders. The lifters cannot be accessed via the valley, so if your task is to service the lifters, don’t bother to remove this top cover.</p>


This view shows the lifter bores, immediately above the cylinders. The lifter bores are covered by the cylinder head.
<p>This view shows the lifter bores, immediately above the cylinders. The lifter bores are covered by the cylinder head.</p>
LS firing order
While consideration of the firing order isn’t particularly relevant when merely servicing lifters, I wanted to point out that the GM LS series of engines feature a different firing order as compared to early-generation smallblock Chevy engines. This is due to the different camshaft firing order, with cylinders 4/7 and 2/3 swapped in order to reduce valvetrain harmonics and to enhance both performance and smoothness.

FIRING ORDER EXAMPLES:
Smallblock/bigblock Chevy
Standard firing order     1-8-4-3-6-5-7-2
LS firing order (OE GM)     1-8-7-2-6-5-4-3

Install lifters before the head gaskets
Be aware that the roller lifters and lifter buckets must be installed before installing the head gaskets, since sections of the gaskets are located above the lifter buckets.

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.

In order to service the lifters, remove the rocker arms and pushrods, then rotate the crankshaft a full 360 degrees. This will allow the camshaft lobes to push the lifters up into the lifter buckets, securing the lifters away from the lobes.
<p>In order to service the lifters, remove the rocker arms and pushrods, then rotate the crankshaft a full 360 degrees. This will allow the camshaft lobes to push the lifters up into the lifter buckets, securing the lifters away from the lobes.</p>

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.

While the rocker arms are removed, inspect the trunion bearings. The OE rockers have a tendency to wear (needle bearings falling out and ending up in the oil pan). This is a good time to inspect and possibly replace the rocker arms.
<p>While the rocker arms are removed, inspect the trunion bearings. The OE rockers have a tendency to wear (needle bearings falling out and ending up in the oil pan). This is a good time to inspect and possibly replace the rocker arms.</p>

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. 

Each lifter bucket well features molded ridges that help to direct oil to the lifters.
<p>Each lifter bucket well features molded ridges that help to direct oil to the lifters.</p>
In the LS family, the plastic “buckets” register the roller lifters to prevent rotation. Other methods of preventing roller lifter rotation (on other OE and/or aftermarket applications/engine types) involve either a pair of lifters connected by a pivoting tie-bar, or more commonly, each pair of lifters being guided by a twin-cavity “dogbone” plate, with these dogbones being held down by a common sheet metal plate that features tensioned “fingers” that prevent the dogbones from moving.
Note that some aftermarket performance lifters may be a tad longer (to allow for higher lift cams) and may require the use of a 6mm-diameter spacer washer between the lifter bucket and the engine block. If required, these lifter bucket bolt spacers will likely be supplied with the lifters. To prevent the spacers from sliding down while trying to align the lifter bucket bolt hole, I dab a bit of Royal Purple Max Tuff lube onto the back of the washers, which prevents them from sliding out of place. Any clean grease will likely suffice simply to secure the washer in place, but do not use any type of adhesive such as RTV, etc.).

Tags: Engines 
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