LS Swap Injectors: How to Choose the Right Fuel for Your Swap

Dropping an LS into an older chassis is the fun part.
Making it start, idle, and live under boost… that’s where injectors come in.

Whether you’re building a budget 5.3 turbo junkyard special or a full-send LS3 street/strip car, your LS swap injectors decide:

• How much horsepower you can safely support

• How cleanly the car idles and cruises

• How much your tuner loves or hates you

This guide walks through what LS swap injectors are, how to pick the right ones, and what to watch out for so you’re not guessing at the fuel system.

What Are “LS Swap Injectors” Exactly?

“LS swap injectors” isn’t a special magic part number—it’s injectors sized and configured to work with an LS engine in a swapped chassis.

Good LS swap injectors are:

• High impedance (High-Z) – so they work with factory-style ECUs and most standalones without resistor boxes

• Available in popular LS sizes like 42lb, 60lb, 80lb, 1000cc, 1200cc, etc., matched to real horsepower goals

• Built on modern bodies (Bosch/DEKA style) that offer good spray patterns and controllability at low pulse widths

• Sold as flow-tested, matched sets so every cylinder gets similar fueling, not “whatever came out of a random bin”

Because LS swaps show up in everything—from S10s and G-bodies to drift cars and drag cars—having the right size and right connectors is what makes the swap actually usable.

Why Injectors Matter So Much in an LS Swap

You can bolt the engine in and hook everything up, but if the injectors are wrong, you’re going to fight:

• Lean conditions at WOT

• Misfires, rough idle, and cold-start issues

• Tuning headaches where nothing quite “sticks”

For LS swaps, injectors are doing three big jobs:

1. Feeding your horsepower goal
   If the injectors are too small, they’ll hit 100% duty cycle long before you hit your power target. That’s where you start seeing “safe” tunes that are secretly right on the edge.

2. Supporting your fuel choice
   E85, race gas, and pump gas all need different volume. E85 especially demands larger injectors to make the same power.

3. Playing nice with your ECU and harness
   High impedance injectors and the correct connector type (EV1, EV6/USCAR, Multec, etc.) keep wiring simple and reduce the chance of signal issues.

How to Choose LS Swap Injectors (The Simple Way)

Instead of just buying “whatever your buddy runs,” use three questions:

1. What’s your honest horsepower goal?

Not your “one day if I win the lottery” number—what you’re actually aiming for in the next 12–18 months.

Roughly:

• Up to ~500 hp: 42lb-ish injectors can work with gas

• 500–650 hp: 60lb DEKA-style injectors are a sweet spot

• 650–800+ hp: 80lb or 1000cc injectors, depending on fuel and BSFC

• 900–1,000+ hp / heavy E85: 1200cc and up

That’s why High Performance Injectors has content around “What size injectors do I need for 500 hp?”, 1000cc, and 1200cc injectors—they’re common decision points in LS builds.

2. What fuel are you running?

• Pump gas only: You can get away with smaller injectors for a given power level.

• E85 / flex fuel: Plan for roughly 30% more fuel volume—so you need bigger injectors at the same hp.

If you know you’re going E85 soon, it’s usually smarter to size for that now instead of buying injectors twice.

3. What ECU and wiring are you using?

For most LS swaps using:

• Factory GM PCMs (P01, P59, E38, etc.)

• Standalone systems like Holley, Terminator X, etc.

…you want high-impedance injectors with proper characterization data. That’s what lets the tuner make big injectors idle like stock when everything’s entered correctly.

Physical Fitment: Lengths, O-Rings, and Connectors

Beyond size and flow, LS swap injectors have to physically fit:

• Body length: Most LS intakes expect a standard “long” EV style injector; some combos use shorties with spacers/adapters.

• O-ring size: 11mm vs 14mm can bite you if you don’t check rail and manifold compatibility.

• Connector type:

  • EV1 (Jetronic)

  • EV6 / USCAR

  • Multec style used on some GM truck stuff

Shops like High Performance Injectors design LS swap injector packages so this is already thought through—no guessing, no “will this actually seat in the rail?” moments.

LS Swap Injectors + Harness: The Power Couple

Injectors are only as good as the wiring feeding them.

If you’re running:

• A crusty, cut-up junkyard harness

• Random splices and adapters

• Weak grounds

…you’ll see weird misfires, random dead cylinders, and tuning nightmares that masquerade as “bad injectors.”

Pairing proper LS swap injectors with a stand alone LS swap harness:

• Ensures stable power and ground to every injector

• Keeps signals clean so the ECU can control pulse width accurately

• Makes diagnosing issues way faster

That’s why HPI leans so hard into harness + injector combos in their LS swap ecosystem—clean wiring plus matched injectors gives builders a solid base to tune from.

Q&A: Can I Just Clean My Stock Injectors for an LS Swap?

Q: If I’m just swapping a stock 5.3 or 6.0 into a car, can I clean the factory injectors and run those instead of buying LS swap injectors?

A: You can—and a proper fuel injector cleaning service is a great idea if you’re staying close to stock power. But:

• If you’re adding boost, cam, or E85, those stock injectors will run out of headroom fast.

• Older injectors might be clogged or uneven, even after cleaning.

• Once you start tuning for serious power, you’ll want modern, flow-matched injectors sized for the new combo anyway.

A smart approach is:

• Service + test old injectors if you’re staying mild.

• Step into proper LS swap injectors when you’re upgrading power or fuel type.

Build Your LS Swap Fueling the Right Way

If your LS swap is more than just a stock cruiser, your injector choice is not the place to wing it.

Dial in:

• Size for your real horsepower goals

• Fuel compatibility (especially E85)

• Fitment for your manifold, rails, and connectors

• Wiring that actually supports the system

Then your tuner can focus on making power instead of fighting bad data and mismatched parts.

👉 Browse flow-matched LS swap injectors, injector cleaning, and LS swap harnesses at
HighPerformanceInjectors.com

💥 At checkout, use code Turbo for 10% OFF qualifying injectors, harnesses, and services.

Feed the swap right, and it’ll pay you back every time you mat the pedal.