Maintenance

Changing a camshaft in the GM LS engine

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Changing a camshaft in the GM LS engine

Servicing a camshaft in any overhead-valve engine requires a degree of disassembly, but in the case of GM’s LS-series of engines, the task is a bit less tedious, since there is no need to remove the intake manifold, upper engine cover or lifters. Here we’ll explain the process.

1. Remove both valve covers.

2. Remove all rocker arms.

3. Remove the following components:

 • Water pump

 • Crankshaft pulley

 • Oil filter

 • Oil pan

 • Front engine cover (timing cover)

 • Oil pickup tube/screen assembly

 • Oil pump

 • Oil pump drive gear (slides off of the crank snout)

4. Rotate the crankshaft two full turns (360 degrees), and position the crank gear and cam sprocket dots (cam gear dot at 6-o’clock and crank gear dot at 12-o’clock). Once positioned, DO NOT rotate the crankshaft at any time during the process. (By rotating the crank two full turns, this causes the camshaft lobes to push the lifters up into the plastic lifter buckets. With no valve spring pressure, since the rockers have been removed, the lifters will “snug” into the lifter buckets, holding the lifters up and away from the camshaft, allowing a clear path for camshaft removal without the need to remove the lifters. Note that in order to remove the lifters, the cylinder heads must be removed. This feature (lifters secured in the buckets) avoids the need to remove the heads). There is no need to remove the intake manifold or the upper engine cover plate. There is no access to the lifters at the top valley, and there’s no need to remove the lifters anyway.

5. Remove the camshaft sprocket and timing chain.

6. Remove the camshaft retaining plate.

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7. The camshaft is now ready for extraction. However, even though the lifters are being held out of the way in their respective buckets, there is still a chance for one or more lifters to accidentally fall out, which would then require cylinder head removal in order to retrieve the lifter(s). In order to avoid this potential problem, carefully insert a pair of 1/4-inch or 5/16-inch-diameter metal rods into the lifter oil galley passages (one rod into the oil galley on each side of the camshaft bore). Use rods that are about 28 inches long (or longer). This serves as a backup. In case a lifter tries to fall, the rod will stop it and keep the lifter engaged in its bucket’s flat registers (keeping the lifter in proper alignment). Leave these rods in place until the new camshaft has been installed.

8. Using a suitable camshaft removal/installation tool/handle, carefully remove the camshaft and avoid dragging the lobes across the cam bearings. Again, proceed slowly and carefully. Scraping a cam bearing will result in a severe oil pressure drop and will require bearing replacement.

9. Before installing the replacement camshaft, coat all cam journals with either clean engine oil or an engine assembly lube. Coat all cam lobes either with clean engine oil or a high-pressure lubricant designed for camshaft break-in. Even though the LS engines feature roller lifters, it never hurts to use a quality high-pressure lubricant.

10. Remove the two temporary metal rods from the lifter oil galleys.

11. By hand, push each pushrod fully downward in order to dislodge the lifters from their buckets, allowing each lifter to contact its cam lobe.

12. Install a NEW camshaft retainer plate. The imprinted sealant on the rear of the plate tends to harden over time, so it’s recommended to always use a new retainer plate. Depending on the version of the engine, the retainer plate bolts may feature a hex head or a Torx head. Hex head bolts are tightened to 18 ft.-lbs., while Torx bolts are tightened to 11 ft.-lbs. In either case, I prefer to apply a drop of medium thread locking compound to all bolt threads prior to installation.

13. Install the camshaft sprocket and timing chain, aligning the timing dots. Tighten the cam sprocket bolts to 18 ft.-lbs. (with thread locker).

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14. Install the rocker arms, tightening all rocker arm bolts to 22 ft.-lbs. NOTE: The intake rocker arm bolt holes in the cylinder heads are open to the intake runners. Apply a thread sealer to all INTAKE rocker arm bolts before installation.

15. Install the oil pump drive gear onto the crank snout (depending on the version, this may incorporate the crank gear, in which case you’ve already installed it during the timing chain installation, or it may be a separate radius-toothed gear that slides on after the crank gear).

16. Install the oil pump to the block (aligning the pump’s floating driven gear to engage onto the drive gear). Install the oil pump-to-block bolts finger tight. Using a feeler gauge, do your best to center the pump relative to the crank snout drive gear (there’s a small bit of slop in the pump’s mounting bolt holes). Then tighten the pump bolts to 18 ft.-lbs.

17. Install the oil pickup assembly, using a new O-ring on the end of the pickup tube where it engages into the oil pump (lube the O-ring with oil first). Engage the pickup tube bracket onto the main stud and install the nut finger-tight. Next, torque the 6 mm bolt that secures the pickup tube to the oil pump at 106 in.-lbs. Then tighten the pickup tube bracket at the main stud to 18 to 20 ft.-lbs.

18. Install the front engine cover, using a new gasket (metal core gasket with an imprinted sealing bead). Initially, install the cover bolts finger-tight. Place a straightedge along the block’s oil pan rail, across the bottom of the front cover in order to verify that the cover’s bottom surface is flush with the oil pan rail. Tighten the front cover bolts to 18 ft.-lbs.

19. Clean the oil pan thoroughly. The oil pan gaskets feature an imprinted elastomer sealing bead and may be reusable, but I recommend installing a new gasket. Before installing the oil pan gasket, apply a small bead of RTV along the joint where the bottom of the front cover meets the block. Install the oil pan gasket and oil pan, tightening the 8 mm bolts to 18 ft.-lbs., and the 6 mm bolts to 106 in.-lbs.

20. Install the crankshaft pulley by drawing the pulley onto the crank snout, using a harmonic balancer installation tool that features a 16 mm x 2.0 thread. NEVER try to force any balancer or pulley into place by striking it with a hammer or other impact tool. Refer to the information on page 46 regarding crankshaft pulley bolts.

21. Once the crank pulley has been installed, install the water pump using two new gaskets. These are aluminum cores with imprinted sealing beads. Even though the old gaskets may appear to be usable, don’t risk it. Install new gaskets. Tighten the water pump bolts in two steps: first tighten all bolts at 11 ft.-lbs., and then at 22 ft.-lbs., tightening in a crisscross manner to spread the clamping load.

22. Finish assembly (belt, valve covers, etc.). Fill a new engine oil filter with the appropriate oil, install the filter and add the appropriate amount of oil to the sump per the specific engine’s specs.

Crankshaft pulley bolt

The LS crankshaft snouts feature a 16 mm x 2.0 thread size. When installing the crank pulley, you have two choices in terms of the pulley bolt: the OE TTY (torque to yield) bolt, or the ARP bolt. My recommendation is to use the ARP bolt.

When using an OE bolt, you must follow a more tedious process, and you’ll need two of these bolts. First (after making sure that the crank female threads are clean), position the pulley onto the crank snout. Install an OE bolt and tighten to a value of 240 ft.-lbs.

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This OE specification is required in order to fully seat the pulley. Next, remove the OE bolt and discard it (it’s a TTY bolt and cannot be reused). Install a new OE bolt and tighten to 37 ft.-lbs., followed by an additional 140-degree turn. The OE bolt requires this torque-plus-angle method. This is tedious, and requires that the crankshaft does NOT rotate during the angle tightening.

The ARP bolt is a high-quality bolt with a high tensile strength, and does not require a torque-plus-angle approach.

Simply lube the bolt threads and the underside of the bolt head with ARP’s engine assembly lube, slip on the provided hardened washer and torque to a final value of 235 ft.-lbs. (You must use this moly lube in order to achieve the desired torque value. Do not use engine oil.)

Granted, the ARP bolt is more expensive than the OE bolt, but it’s more dependable, much easier to install (no torque/angle process to mess with), and does not require a “donor” bolt for initial tightening. This bolt can be reused during future service, unlike the OE bolt.

NOTE: All wet-sump LS engines (LS1, LS6, LS2, LQ4, LQ9, etc.) require a 16 mm x 2.0 bolt that features a shank length of 4.325 inches. All dry sump LS engines (LS7, etc.) require a longer 5.225-inch bolt to accommodate the pump drive.

If purchasing the ARP bolt, the part number for the wet sump engines is 234-2503. The dry sump engines require P/N 234-2504.



ARP crank pulley bolt, 235 ft.-lbs. (with ARP moly)

Camshaft retainer bolts (Torx), 11 ft.-lbs.

Camshaft sprocket bolts, 18 ft.-lbs.

Oil pump pickup tube to main stud nut, 18 to 20 ft.-lbs.

Oil pump pickup to oil pump bolt, 106 in.-lbs.

Oil pump to block bolts, 18 ft.-lbs.

Front engine cover bolts, 18 ft.-lbs.

Oil pan 6 mm bolts, 106 in.-lbs.

Oil pan 8 mm bolts, 18 ft.-lbs.

Oil pan drain plug, 18 ft.-lbs.

Water pump bolts, 11 ft.-lbs., then 22 ft.-lbs.

Rocker arm bolts, 22 ft.-lbs.   ●

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