Cam tuning for an LS swap
A cam changes how the engine breathes, so the tune and a few supporting parts have to follow.
What changes
- The tune: PCM must be recalibrated to stop commanding deactivation; aftermarket cams also need idle, fuel, spark and torque-model changes.
- AFM engines: Gen IV AFM engines need an AFM delete to run aftermarket cams; many also delete VVT, which requires a Gen 3-style timing cover in place of the VVT cover with integrated phaser. See the AFM delete parts list.
- Cam bolt: AFM engines use a single-bolt cam; a three-bolt performance cam needs a matching three-bolt gear and chain. Gen IV moved the cam sensor to the front cover.
- Torque converter: match the stall speed to the cam and powerband; a bigger cam wants more stall. See transmission tuning.
- Springs and injectors: use the springs the cam maker specifies; Speedway notes stock truck injectors are near their limit even for a hot cam swap.
Cam tuning cheat sheet
What the cam makers say about converters, idle and springs. Each cam's page has its own checklist.
Show the cam tuning cheat sheet
Blank means the maker didn't say. Browse every cam in the cam finder.
What the sources say
Paraphrased from the linked sources (10 points). Specifics depend on your computer and operating system.
Show all
- LS Gen III/IV; 1997-2013: With a MAP sensor for load sensing, stock-cam engines typically idle at 17 to 21 inches of vacuum, while cams with more overlap and duration drop idle vacuum into the 8 to 15 inch range. SDS EFI
- LS Gen III/IV; 1997-2013: On a cammed engine, vacuum rises in the 1250-2000 rpm no-load/light-load band; if the fuel map progresses linearly with MAP like a stock engine's, the system delivers less fuel when the engine actually needs more, creating a lean spot just off idle that requires extra fuel just above idle RPM. SDS EFI
- LS Gen III/IV; 1997-2013: A hotter cam raises airflow rates across the range, so fuel flow must rise to match; the fuel curve ramps more steeply and peaks at a higher RPM than the stock cam's fairly linear curve. SDS EFI
- LS Gen III/IV; 1997-2013: With a very hot cam (for example 6 inches of idle vacuum), MAP-based load sensing degrades because pressure fluctuations in the plenum are too intense and only about a quarter of the sensor's range is used, so throttle-position load sensing can be easier to program. SDS EFI
- LS Gen III/IV; 1997-2013: The Sniper calibration wizard offers camshaft selections tied to manifold vacuum: Stock/Mild for stock or street performance cams, Street/Strip for 8-13 inches of vacuum, and Race for under 7 inches of vacuum, with race cams possibly needing laptop tuning for idle stability. Holley
- LS1; 2000-2002: The desired idle speed is influenced by accessories such as air conditioning and by cam selection; a bigger cam typically wants a higher idle target. LSX Magazine
- LS Gen III/IV; 1997-2013: Any modification that significantly changes airflow or fuel flow, such as injector size, camshaft, or throttle body, requires a custom calibration because the stock fuel-flow and timing data will be off the mark. LSX Magazine
- LS Gen III/IV; 1997-2013: The Desired Idle Speed table is the first stop after a performance cam install: a stock cam idles happily at 525-550 rpm, while a performance cam needs roughly 750-850 rpm depending on duration. LSX Magazine
- LS Gen III/IV; 1997-2013: A fuel trim split is a large difference in fuel correction from one bank to the other, which usually points to a vacuum leak that should be found with a smoke tester before tuning proceeds. PCM of NC
- LS Gen III/IV; 1997-2013: A proper tuning datalog should be 15 to 20 minutes long and cover all operating states including cold start, idle, cruise, part throttle, and wide-open throttle where safe. PCM of NC
Sources
- 6.0 LS Build Combinations: Recipes for 500-1,000 HP — Speedway Motors
- Ask Away! How to Delete the AFM System in a 5.3L LS Truck Engine (Jeff Smith) — OnAllCylinders (Summit Racing)
- DOD, AFM, And DFM Deletes: A Q&A With Michigan Motorsports — LSX Magazine
- GM AFM Explained | How It Works, Why It Fails & How to Delete It — Speedway Motors
- Vortec 4.8 LS Build: Horsepower Recipes, Specs and Upgrades — Speedway Motors
- How to Choose a Torque Converter — Speedway Motors
- Late-Model Tuning 101 With EFILive — LSX Magazine
- Remote (Email) Tuning with HP Tuners FAQ — PCM of NC
- LS Tuning For Optimum Performance — LSX Magazine
- Tech Page - Fuel Values vs. Camshafts — SDS EFI
- Holley EFI Systems Installation Instructions (Sniper EFI Quickstart Manual) — Holley