500 HP LS3 Naturally Aspirated — The Complete Parts List

TL;DR: A 500 crank-horsepower naturally aspirated LS3 is a top-end build, not an engine build. The factory 6.2L short block — nodular crank, powdered-metal rods, hypereutectic pistons — is not the limiting part at this power level, so the money belongs in the camshaft, the valvetrain that has to survive it, and the cylinder heads. Two paths get there: a well-chosen cam package on the stock rectangle-port castings, or a cam plus CNC-ported or aftermarket heads that clears 500 with margin. The parts list below covers both, and it deliberately tells you which popular line items to skip.

The Argument: This Is a Cylinder Head Problem

The LS3 leaves the factory at roughly 430 crank horsepower from 376 cubic inches — about 1.14 horsepower per cubic inch, already strong for a production pushrod V8 on a pump-gas, catalyst-compatible calibration. Getting to 500 means finding 1.33 hp/ci.

That is a modest ask by naturally aspirated standards, and saying why determines where the money goes. The LS3 is not power-limited by its bottom end at 500 horsepower. It is limited by three things, in this order:

1. Cam timing. The factory grind is a low-lift, short-duration, idle-quality-and-emissions camshaft. It is the single largest restriction on the engine.
2. Valve spring capability. The stock beehive springs were specified for the stock cam's lift. They are why cam-only LS3s eat valvetrain when people economize here.
3. Head flow above roughly 0.550 in lift. The stock LS3 rectangle-port castings flow genuinely well — this is the good factory head — and they are the reason a cam-only LS3 gets close to 500 at all.

Everything else on the parts list exists to support those three items, or to keep the engine alive while they do their work.

What You Should Not Buy

This is the section that saves the most money, so it comes first.

Forged pistons and rods. The factory LS3 rotating assembly is not the weak point at 500 naturally aspirated horsepower. The powdered-metal rods and cast crank live in the field at this power level and past it, and the loads that break them are boost and detonation, not naturally aspirated cylinder pressure at stock compression. A forged short block here is insurance against a failure mode this build does not have. If the block is already apart the math changes — but do not pull a healthy engine to install parts it does not need. Browse pistons when the short block is genuinely coming apart.

Bigger injectors. Run the numbers rather than the forum advice. At 500 crank horsepower with a naturally aspirated brake-specific fuel consumption of roughly 0.45 lb/hp-hr, the engine burns about 225 lb/hr of gasoline total, or 28 lb/hr per injector at 100 percent duty cycle. Sized to a sane 80 percent maximum duty, you need injectors of about 35 lb/hr. The factory LS3 injector is 42 lb/hr. It is already large enough.

Head studs. ARP studs are the right call on a boosted iron-block engine holding a gasket against serious cylinder pressure. On a naturally aspirated aluminum LS3 at stock compression, head clamping is not what fails. What matters is that the factory head bolts are torque-to-yield and single-use: if the heads come off, they do not go back on with the old bolts. A fresh bolt kit — ARP 234-4316, CPP-LS-STUD-ARP-137 — is the correct spend; the M11 stud kit CPP-LS-STUD-ARP-136 is the spend for a boosted build you are not doing. See head studs and bolts.

A big aftermarket intake. The factory LS3 composite manifold (CPP-LS-INTAKE-GMOEM-192) is genuinely good and does not become the restriction at 500 naturally aspirated horsepower on a street cam. The rectangle-port manifolds in intake manifolds earn their money above this power level.

Path A: Cam Package on Stock Heads

This is the cheaper path and the one most 500 hp LS3s actually take: the factory rectangle-port castings, a well-matched cam, a spring package that supports it, and a calibration.

Expect it to land in the high 400s to low 500s at the crank, depending heavily on exhaust and tune. A cam-only LS3 with factory manifolds and a stock exhaust does not make 500. Long-tube headers and a real exhaust are part of this number, and neither is an engine part — budget them separately.

Choosing the grind

Every cam below is a real rectangle-port grind from our catalog. Read the table as a duration-and-LSA comparison, not a horsepower ranking.

Two notes. First, the Stage 2 grinds from BTR and Texas Speed sit within a few degrees of each other — the brand argument matters far less than people think, as we worked through in COMP Cams vs BTR vs Texas Speed. Second, the catalog carries a COMP XFI grind named for AFM delete duty (CPP-LS362LGenIV58x-CAM-COMP-01, .605/.615, 114 LSA) tagged to LS3. The LS3 was never built with Active Fuel Management, so that name describes the lobe family's origin rather than a job your engine needs — the grind itself is a usable mild rectangle-port cam. Confirm the intended application before ordering that row.

The valvetrain that has to survive it

This is the part of the build people underspend on, and it is where cam-only LS3s fail.

On pushrod length: 7.400 in is the LS default, not the LS answer. Any change in valve length, spring seat machining, head milling, or head gasket thickness moves the required length. Check it with the tool, then order — our rocker arm preload guide covers the measurement. Browse pushrods once you have a number.

On piston-to-valve clearance: the stock LS3 piston has shallow valve reliefs. At .630 in lift on a 112-degree lobe separation angle, clearance is a real check rather than a formality — clay cylinder one before final assembly. Check your minimum clearance target against the cam manufacturer's recommendation for your rocker ratio.

On dual springs and the stock LS3 head: most dual spring packages have a larger outside diameter than the factory beehive, and installing them on unmachined LS3 castings can require the spring seat to be cut. Confirm with your machinist before the heads leave the bench. Confirm the required seat diameter against the specific spring package you buy — see valve springs.

Path B: Cam Plus Ported or Aftermarket Heads

This is the path that clears 500 with margin instead of reaching for it, and it is the honest recommendation if you are already paying for a cam, springs, and the labor to open the top end.

Two things decide this table, and neither is peak flow. The first is chamber volume, because it moves static compression: the 68cc castings hold compression where the 70cc castings give a little back — and on a naturally aspirated engine, compression is free power you have already paid for. The second is minimum bore, because most aftermarket rectangle heads specify a bore floor at or above the LS3's 4.065 in, and the valves shroud or contact below it. We compared these castings in AFR 245 vs Trick Flow 255 vs Brodix BR7; browse the full set under rectangle-port cylinder heads.

Buying assembled heads is usually correct here: it bundles valves, springs and retainers into a matched package and removes the spring-seat machining question from Path A entirely. If you go bare, add valves — CPP-LSGen4-VALVES-FERREA-04 (2.165 in intake) and CPP-LSGen4-VALVES-FERREA-05 (1.59 in exhaust) — and budget the assembly labor.

Supporting Parts and the Fuel Math

Two notes. The oil pump pickup tube is the actual LS killer, not the pump: a cracked braze or a failed O-ring at the pickup starves the pump long before the pump wears out. Replace that O-ring whenever the pan is off — see oil pumps and our Melling vs Boundary vs Moroso comparison.

The crank flange bolt pattern is a genuine ordering trap here. Late LS3 applications moved to an eight-bolt crank flange, and those flexplates and flywheels do not interchange with the six-bolt parts. Count your bolts before ordering either — the catalog carries both (CPP-LS-FLEXPLATE-ATP-92 eight-bolt, CPP-LS-FLYWHEEL-MCLEOD-107 manual).

Injector sizing, worked

Check BSFC against your own dyno data — 0.45 is a reasonable naturally aspirated planning figure, not a measured constant. If you are on pump gasoline, keep the factory injectors. If you are converting to E85, CPP-LS-INJECTOR-SIEMENSD-269 (Siemens Deka Mk2, 60 lb/hr) is the smallest correct step and the fuel pump becomes the next question. Browse fuel injectors.

Order of Operations

1. Decide Path A or Path B before buying anything. The head decision changes the cam, the springs, and possibly the pushrods.
2. Order the cam and springs together, so the spring package matches the grind's lift rather than a generic "LS spring" recommendation.
3. Measure pushrod length with the checker after the heads and cam are in. Do not pre-order pushrods.
4. Clay-check piston-to-valve clearance on cylinder one before final assembly.
5. Set rocker preload deliberately — it is a specification, not "one turn past zero lash."
6. Replace the oil pump pickup O-ring while the pan is off.
7. Calibrate. A cam swap without a tune runs the factory's airflow model against an airflow curve the engine no longer has.

FAQ

Will a cam-only LS3 make 500 horsepower? On a stock exhaust, no. With long-tube headers, a full exhaust, a well-matched rectangle-port grind, a proper spring package and a calibration, a cam-only LS3 lands in the high 400s to low 500s at the crank. Cylinder heads are what put 500 comfortably behind you rather than exactly at the edge.

Do I need forged pistons for 500 naturally aspirated horsepower? No. The factory LS3 rotating assembly is not the limiting component at this power level naturally aspirated. Forged internals become the right answer when you add boost, raise compression significantly, or have the engine apart anyway.

Do I need bigger injectors? Not on pump gasoline. At 500 crank horsepower the engine needs roughly 35 lb/hr injectors sized to 80 percent duty cycle, and the factory LS3 injector is 42 lb/hr. E85 changes the answer — that fuel needs roughly 50 lb/hr per injector at the same power.

Are head studs required? Not for a naturally aspirated LS3 at stock compression. What is required is new head bolts if the heads come off, because the factory bolts are torque-to-yield and single-use.

What pushrod length do I need after an LS3 cam swap? It has to be measured. 7.400 in is the common factory-equivalent length, but new valves, spring seat machining, milled heads, or a different head gasket thickness all move the target. Use a length checker, then order.

Will the factory intake manifold hold back 500 horsepower? No. The LS3 composite manifold is a genuinely capable piece and it is not the restriction at this power level on a street cam. An aftermarket rectangle-port manifold pays off above this number or at higher engine speeds.

Does the LS3 need a VVT-delete kit? No. The LS3 is a non-VVT engine, so it takes a standard Gen IV 58x non-VVT timing set. VVT-delete kits are for the L76, L92, L94 and LY6 family. Ordering a VVT part for an LS3 is a common cart mistake.

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