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Making power with an LS: build recipes

Proven paths from stock to 400, 500 and 600+ hp, and what breaks along the way.

Build recipes

Build facts

• Stock 5.3 is rated around 320 hp / 340 lb-ft; stock 6.0 around 300 hp / 360 lb-ft, depending on version and year (Speedway generalization) (Engine table ranges differ by RPO (e.g., LQ9 345 hp); use per-RPO data where possible)
• Junkyard LM7 5.3 made 430 hp with a simple cam swap (Speedway C10 project; BTR Truck Norris)
• LS4 (2005–2009 FWD Impala SS/Monte Carlo SS/Grand Prix GXP) is not recommended for RWD swaps; different bellhousing bolt pattern among other issues
• 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
• Stock LS fuel filter/regulator assembly tops out around 450 hp; beyond that, larger lines and an external regulator
• Project Chevelle LQ9: fresh pistons, rings, bearings and a COMP cam made 496 hp / 460 lb-ft
• LFA/LZ1 hybrid 6.0s (aluminum, cathedral heads) are only recommended if nothing else is available; plan a different cam and custom accessory drive
• AFM (introduced 2005 in Tahoe-class SUVs) deactivates both valves on four cylinders using oil-pressure-controlled lifters fed by the LOMA/VLOM valley-cover manifold
• A proper AFM delete: non-AFM camshaft, all 16 conventional roller lifters (not just the 8 AFM lifters), new lifter trays, and blocking the deactivation oil circuit (non-AFM valley cover or plugs); heads must come off, so head gaskets, head bolts and exhaust gaskets too
• Plugging the oil passages while keeping AFM lifters is not a delete: the collapsible mechanism remains and oil can back-feed into the DOD channels and collapse lifters later
• Add GM oil-pan pressure-relief-valve cap (12639759) when deleting AFM to stop oil spray/consumption; replace the pickup O-ring
• 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
• PCM must be recalibrated to stop commanding deactivation; aftermarket cams also need idle, fuel, spark and torque-model changes
• Failing AFM lifter: single-cylinder misfire, persistent tick, rough idle, low power, cylinder-specific misfire code; can progress to bent pushrods, cam lobe wear and metal in the oil
• Summit AFM delete kit (no cam) CMB-09-0026: 16 lifters, new lifter guides, head bolts, LS3-style valley plate
• Speedway 5.3 guide calls the L33 a Gen IV engine and the LC9 an iron-block engine (GM engine tables (Wikipedia) list L33 as Gen III and LC9 as aluminum)
• LS mount bosses are roughly where SBC mounts were; common adapters convert the LS block to the classic three-bolt Chevy mount; adapter hole offsets move the engine fore/aft
• Junkyard LS pans often hang too low (sump depth) for muscle cars/hot rods; low-profile swap pans fit most chassis; baffled/ventilated pans help oil control in hard cornering
• Accessory drive spacing: Camaro/F-body about 0.750 in farther from the block than Corvette; truck about 1.5 in farther
• Most LS water pumps have both inlet and outlet on the passenger side; LS swap radiators put both ports on the passenger-side tank
• Speedway: LS upper hose is 1-1/4 in (smaller than SBC/BBC) (ICT Billet says the upper hose connection on all LS pumps is 1-3/8 in)
• LS thermostat sits low on the water pump, so a steam line is needed to purge trapped air; most LS swap radiators have a steam port, and adapters let universal radiators work
• LS keeps the same bellhousing dowels and 5 of 6 bolt holes as SBC/BBC, but the crank flange sits farther forward; autos need a dished flexplate + converter sleeve adapter to run TH350/400/700R4; manuals need an LS-specific bellhousing (e.g., OER, Quick Time) for older 4-bolt GM or TKO boxes
• Exception: 1999–2000 LQ4 6.0s have a "long" crank flange and use a flat flexplate with no dish or spacer
• Crank reluctor is 24x or 58x; the ECU must match. Tell by the crank sensor (behind the starter): early black 24x, later gray 58x
• LS can run a carburetor: Edelbrock Performer RPM / Victor Jr. carb intakes, Holley options, and an MSD standalone ignition box for the coil-near-plug ignition
• LS EFI needs about 58 psi vs 5–7 psi for a carbureted small block; parts-store hose clamps/rubber hose are not adequate at 60 psi. Use AN hardlines, push-on hose/fittings, or ethanol-safe hose (e.g., Earl's Vapor Guard)
• Follow ECU maker wiring exactly; go heavier on wire gauge when in doubt; soldered + heat-shrink connections beat cheap crimps
• The PCM reads crank, cam, MAF, coolant, IAT and O2 sensors to control fuel, spark and idle (and shifts on automatics); on drive-by-wire engines it also controls the throttle
• Every donor PCM needs reprogramming: delete VATS (or the engine will not start), match injector size and MAF scaling, and match transmission settings; emissions monitors and speed limiters from the donor are also present
• 24x (Gen III: LS1, LS6, LQ4, LQ9, Vortec trucks through 2006) uses a 1x cam sensor; 58x (Gen IV: LS2, LS3, LS7, LS4, L76, L92, 2007+ Vortec trucks) uses a 4x cam sensor. PCM, harness and sensors must match; a Gen III PCM on a 58x engine needs a conversion box
• Gen III: black crank sensor, cam sensor at the rear of the block. Gen IV: gray crank sensor, front-mounted cam sensor, EV6-style injectors, six-pin drive-by-wire throttle
• Drive-by-cable: throttle opened mechanically (early Gen III trucks, Camaro LS1). Drive-by-wire: PCM opens the throttle from a pedal-position sensor (all Gen IV). A DBW swap needs the pedal wired and calibrated (PSI also says "most LS1/LS6" are DBW; C5 Corvette LS1 was DBW while F-body LS1 was cable; treat per-application)
• Very cheap (~$150) harnesses with thin wire and knockoff connectors cause intermittent misfires, no-starts or worse; quality standalones use proper-gauge wire (TXL), new Delphi connectors and are tested
• A standalone harness keeps only the circuits the engine needs to run, removing body-specific donor wiring
• Gen II LT1/LT4 (1992–1996) are not LS engines: cable throttle, EV1 injectors, different harnesses
• Melling M295: stock-replacement LS pump, standard volume/standard pressure
• Melling 10295: standard volume, higher pressure (upgrade with optional pressure springs)
• Melling 10296: high volume, ~18% more flow than stock (~8 GPM vs ~6.8 GPM), ships with a stiffer spring (+10% max pressure / "+10 psi"), stock spring included; designed for single-roller timing chains (double roller may need timing-cover mods); for 1999–2016 4.8/5.3/5.7/6.0/6.2
• Melling 10355: high-pressure pump for 2005–2017 Gen IV 5.3/6.0/6.2 with AFM and VVT (need higher pressure); +10 psi spring installed, stock and +20 psi springs included; 10355HV variant exists
• Melling 10294: 15% LOWER volume, for aftermarket blocks with priority main oiling (GM LSX, Dart LS Next)
• Factory LS oil pump cavitates above ~6,200 rpm (flow drops nearly 1 GPM by 7,000 rpm); Improved Racing advises not shifting above 6,200 rpm on a stock pump
• High-volume pumps can accelerate oil starvation in racing by emptying the sump faster

Engine build questions

• Which LS engine is best for turbo/boost?
• How much horsepower does a stock 5.3 make?
• How much horsepower can a stock 5.3 handle?
• How much boost can a stock 5.3 handle?
• Junkyard 5.3 turbo build: what do you need?
• Best cam for a 5.3
• What is a truck cam?
• 243 vs 799 vs 706 vs 317 heads
• Best budget LS heads
• Truck intake vs LS6 intake
• What is AFM/DFM, and should I delete it?
• Best cam for an LS3?