How to Replace the Camshaft on an LS Gen IV
TL;DR: An LS Gen IV cam swap is mechanically simple and logistically fussy. The cam itself slides out the front of the block once the radiator stack, accessory drive, damper and front cover are out of the way. The hard parts are keeping the lifters from dropping out of their trays, deciding up front what you are doing about AFM and VVT, and re-checking pushrod length and piston-to-valve clearance instead of assuming the stock numbers still apply. Gen IV blocks differ from Gen III in reluctor count and cam sensor location, so the sensor, front cover and timing set have to match the engine you actually have. Plan on a tune afterward; the PCM will not sort out a new cam on its own.
Know which Gen IV you are working on before you order anything
"Gen IV" covers a wide spread of engines — LS2, LS3, L92, LS7, LS9, LSA and the whole truck family including LY6, LC9, LMG and LH6. They share the architecture but not the front-of-engine hardware, and that is exactly where a cam swap lives.
Three questions decide your parts list.
Does it have AFM (Active Fuel Management, also called DOD)? If the valley holds a lifter oil manifold and the engine has collapsible lifters on four cylinders, you are choosing between keeping AFM and deleting it. Most people deleting it do the cam at the same time, because the engine is already open down to the lifters.
Does it have VVT? Later Gen IV truck engines and some car engines use a cam phaser at the front of the camshaft. A VVT cam and a non-VVT cam use different front bolt patterns and different timing sets. You cannot mix them — the cam, the timing set and the front cover hardware are one decision, not three.
What is the reluctor and cam sensor arrangement? Gen IV engines use a 58x crank reluctor and place the cam position sensor at the front of the engine, where Gen III used a 24x reluctor with the cam sensor at the rear of the block valley. That difference changes which front cover, sensor and timing set you buy, and it is the single most common ordering mistake on this job. Confirm the current part number for your specific engine and model year against the manufacturer catalogue before you order — Gen IV spans several years of running changes.
Browse LS Gen IV parts filtered to your engine rather than shopping generic LS listings, and cross-check the camshafts you are considering for VVT versus non-VVT before you add anything to a cart.
The decision table: what each feature forces you to buy
| What your engine has | What the cam swap forces | Notes |
|---|---|---|
| AFM, keeping it | AFM-compatible cam grind, AFM lifters and trays reused or replaced | Limits your cam selection; the AFM lifters must be in good order |
| AFM, deleting it | Non-AFM cam, full set of standard lifters, non-AFM lifter trays, valley cover without the oil manifold provision, plus a tune | The most common Gen IV cam swap path; see LS AFM delete kits |
| VVT, keeping it | VVT cam with the phaser bolt pattern, VVT timing set, phaser inspected or replaced | Phaser condition matters; a worn phaser will not hold commanded timing |
| VVT, deleting it | Non-VVT cam, non-VVT timing set, correct cover and sensor provisions, plus a tune | Confirm the exact delete hardware for your engine and year against the catalogue |
| Any Gen IV, higher-lift cam | Valve springs rated for the lift, possibly new retainers and seals, pushrod length re-check | Coil bind and retainer-to-seal clearance are checks, not assumptions |
| Stock rocker arms retained | Trunnion condition inspected; upgrade is a sensible pairing while apart | Stock needle bearings are a known weak point under higher spring loads |
Parts to have on the bench before you start
Do not start this job with just a cam in a box. At minimum:
- The camshaft, matched to AFM and VVT status and to your intended use. If you would rather buy a matched combination than assemble one, look at cam and valvetrain stage kits.
- A new timing set of the correct type for your engine.
- Lifters and trays if you are deleting AFM, or if the existing lifters have mileage or a history you are unsure of.
- Valve springs rated for the cam's lift, with matching retainers and seals if the spring change requires them.
- Gaskets and seals — front cover, valley cover, valve covers, intake, and the front crank seal.
- An adjustable checking pushrod, plus the pushrods you will actually run once you have measured.
- The correct cam position sensor and O-ring if yours is being disturbed or is original.
- Assembly lube, engine oil, coolant, and a torque wrench you trust.
If your rocker arms are original and you are raising spring pressure, price rocker arms and trunnion kits into the job now rather than doing this work twice.
The sequence
1. Depressurize and drain. Relieve fuel pressure, disconnect the battery, drain the coolant, and drain the oil if the engine is coming apart far enough to warrant it.
2. Get access to the front of the engine. In the vehicle, that means the cooling stack, the accessory drive and belt, and enough clear space ahead of the damper to pull the camshaft straight out. Many people slide the core support forward instead of fully removing the radiator and condenser, so the air conditioning system stays charged and closed. Whichever route you take, you need roughly the length of the camshaft in clear space ahead of the block.
3. Remove the intake, valve covers and valley cover. Label connectors as they come off. On an AFM engine, this is where the lifter oil manifold comes out.
4. Back off the rockers and pull the pushrods. Keep them in order if there is any chance you are reusing them. With the rockers loose, the lifters are free to move.
5. Retain the lifters. This is the step that ruins the job when it is skipped. Once the camshaft leaves, nothing holds the lifters up, and a lifter that drops into the crankcase or falls out of its tray means pulling a cylinder head or dropping the pan. Use proper lifter retaining tools, or the common workaround of keeping the engine level and drawing the lifters up in their trays before the cam moves. Verify every lifter is held before you touch the camshaft.
6. Remove the damper, front cover and timing set. Rotate to the timing marks and note the alignment before anything comes apart. Use a proper damper puller — do not lever the damper off.
7. Pull the camshaft. Thread a long bolt or a cam handle into the cam nose and draw it straight out, supporting the far end as it clears. Do not let the lobes drag across the cam bearings on the way out. That is how bearings get scored on a job that had nothing wrong with them.
8. Inspect while it is open. Look at the cam bearings, the lifter bores, the old lobes and the faces of the old lifters. A lobe with visible wear, or a lifter face with a pit, tells you something about why you are here and about whether debris has gone through the oiling system.
9. Install the new camshaft. Coat the lobes and journals per the cam manufacturer's instructions, and feed it in with the same care you took removing it. Install the timing set with the marks aligned exactly as specified for that set, then torque the cam sprocket and timing components in the factory sequence to the values in the service manual.
10. Front cover, seal and damper. New front seal, the correct sealant where the service manual calls for it, and the damper installed with the proper installation tool rather than hammered on. Torque the damper bolt using the manufacturer's procedure, including any angle stage it specifies.
11. Check pushrod length and piston-to-valve clearance. Use the adjustable checking pushrod to establish the correct length for the new geometry rather than assuming the stock length still works. On an aggressive cam, check piston-to-valve clearance with clay, and confirm the valve springs will not go into coil bind at maximum lift.
12. Reassemble and torque everything in sequence. Rockers, valley cover, intake, valve covers — factory sequence and factory values throughout.
13. Fluids, then start-up. Refill oil and coolant, prime as your procedure calls for, and confirm oil pressure on start-up before you let it run. Bring it up to temperature, watch for leaks, and follow any varied-rpm break-in your cam or lifter supplier specifies.
14. Tune it. A cam change alters volumetric efficiency, and an AFM or VVT delete changes what the PCM is allowed to command. The engine will run without a tune; it will not run correctly, and in a delete it may not run at all without the corresponding calibration changes.
Where these jobs go wrong
Ordering Gen III parts for a Gen IV engine is the leading cause of a stalled swap — reluctor count and cam sensor location are not interchangeable. After that comes lifter retention, then pushrod length taken on faith, then valve springs that were fine for the old cam and are not fine for the new one. None of those are difficult problems. All of them are expensive to discover after the front cover is back on.
The other quiet one is doing the camshaft without doing the timing set. The chain and sprockets have exactly the same mileage as the cam you just decided was not good enough. Replace them together, and shop the rest of the job from one place — LS engine parts covers the Gen III and Gen IV families side by side so you can confirm you are buying to the right generation.
Frequently Asked Questions
Can you replace the camshaft on an LS Gen IV without pulling the engine? Yes, in most chassis. The camshaft comes out the front of the block, so what you need is clearance ahead of the engine rather than an engine hoist. In tight engine bays the core support is slid forward or removed to gain that length.
Do I have to delete AFM when I change the camshaft? No. AFM-compatible cams exist, and keeping AFM is a valid choice if the system is healthy. Most people deleting AFM do it during a cam swap simply because the engine is already open to the lifters and valley, and the labour overlap is nearly total.
Will a Gen III camshaft fit a Gen IV block? The two generations share basic architecture, but the front bolt pattern, sensor arrangement and reluctor differences mean this is not a straightforward swap. Confirm the specific application against the manufacturer catalogue rather than assuming interchange.
Do I need new lifters with a new camshaft? New lifters are strongly recommended any time the camshaft is replaced, and they are effectively mandatory if you are deleting AFM or if the old lifter faces show any wear or pitting. Reusing lifters on a new cam pairs old wear patterns with new lobes.
Do I need a tune after an LS Gen IV cam swap? Yes. A cam change alters airflow, and AFM or VVT deletes change what the PCM is allowed to command. Budget for the calibration as part of the job, not as an optional extra.
How long does the job take? In the vehicle, most shops quote it in the range of a long day to two days of labour depending on the chassis, whether AFM is being deleted, and how much of the front end has to come apart. Truck platforms with the intake and valley to strip generally run longer than car platforms.
Sources
Written from the Core Powertrain Parts technical reference notes on GM Gen III and Gen IV small block architecture, the AFM and VVT hardware differences recorded in our engine-family fitment data, and standard cam-swap practice as specified in camshaft and lifter manufacturers' own installation instructions. All torque values, clearances and part numbers should be confirmed against the factory service manual and the current manufacturer catalogue for your specific engine and model year.
Questions on which camshaft, timing set or lifter package matches your engine? Email sales@coretransmissionparts.com. Orders over $70 ship free.