Best Dual-Injector LS3 Intake Manifold for Turbo and Supercharged Builds: Granatelli ZILLA vs. Holley Lo-Ram

If you are building a turbocharged or supercharged LS and your fuel system has outgrown 8 injectors, you need an intake manifold built for dual injection: two injectors per cylinder, 16 total. The question most builders search is simple: what is the best dual-injector LS intake for boost?

The honest answer starts with your cylinder heads. This guide compares the Granatelli ZILLA billet intake manifold with Holley's Lo-Ram dual-injector manifolds, the option most often recommended for boosted LS builds, so you can pick the right one for your engine.

Step 1: Cathedral Port or Rectangle Port?

LS intake manifolds are built for one cylinder-head port shape, and the wrong one will not bolt up.

• Cathedral port (tall, narrow ports): LS1, LS2, LS6, LQ4, LQ9, LM7 and other early Gen III/IV engines.
• Rectangle port (square-shaped ports): LS3, L99, L76, L92, LSA, LS9, L94, L77 and other later Gen IV engines.

This matters because the best-known dual-injector manifold, the Holley 300-624 / 300-625 Lo-Ram, is a cathedral-port manifold for LS1/LS2/LS6 heads. If you are running a rectangle-port LS3, L99 or L76, you need a rectangle-port manifold, and that is exactly what the Granatelli ZILLA and MEGAZILLA are built for.

Granatelli ZILLA vs. Holley Lo-Ram: Rectangle-Port Dual-Injector Comparison

Here is how the ZILLA lineup compares with Holley's rectangle-port dual-injector Lo-Ram base (300-683), using published specs and prices as of November 2026.

Holley specs and price from the Big3 Racing listing for part 300-683 as of November 2026. Always confirm current specs and pricing with the seller.

Why Billet Matters on a Boosted LS

A boosted intake manifold is a pressure vessel. Every psi of boost pushes outward on the plenum walls, and a backfire under boost can hit the manifold even harder. The ZILLA is machined from solid billet aluminum and carries a published 45 psi boost rating, so you know what it was built to hold before you turn the boost up.

The Holley Lo-Ram is a well-proven cast design and costs less up front. If your build is staying at moderate boost and budget comes first, it is a reasonable option. If you are chasing big boost numbers, running a 120mm throttle body, or want a manifold with a published boost rating, the ZILLA is built for that job.

Why Dual Injection?

Eight injectors can only flow so much fuel, especially on E85, which needs roughly 30% more fuel than gasoline. Dual injection splits the fuel delivery across 16 injectors so each one works in a comfortable duty-cycle range, and it gives you room to grow without changing the manifold.

The ZILLA comes with injector plugs so you can run 8 injectors today and fill all 16 ports when your power goal or fuel choice demands it. The fuel rails are already set up for all 16.

Which ZILLA Should You Choose?

• ZILLA 105mm (980105 black / 980105S silver): the starting point for most boosted LS3, L99 and L76 street and strip builds. Pair it with a Granatelli 105mm LS throttle body.
• ZILLA 120mm (980120): for engines moving more air than a 105mm throttle body can feed. Pair it with the Granatelli 120mm LS throttle body.
• MEGAZILLA (980103): twin 103mm inlets for extreme combinations that have outgrown a single throttle body. It fits the same vehicles as the ZILLA and is also rated to 45 psi.

Still deciding between inlets? Read ZILLA 105mm vs. 120mm vs. MEGAZILLA.

Direct-Fit Vehicles

The ZILLA and MEGAZILLA directly fit factory LS3, L99 and L76 vehicles, including the 2008–2013 Corvette (excluding Z06 and ZR1) and Grand Sport, 2010–2015 Camaro SS (LS3 manual, L99 automatic, including convertible and 1LE), 2014–2017 Chevrolet SS sedan, 2008–2009 Pontiac G8 GT and 2009 G8 GXP, and 2007–2009 L76-equipped Silverado 1500, Sierra 1500, Avalanche, Suburban 1500 and Yukon XL 1500. Australian Holden and HSV L76/LS3 models are listed on each product page.

Common Mistakes

• Buying by displacement instead of port shape. A 6.0L can be cathedral port (LQ4) or rectangle port (L76). Check the heads, not the badge.
• Skipping the tune. A tune is required after installing any of these manifolds.
• Undersizing the fuel system. Sixteen injectors only help if the pump and lines can keep up.
• Mismatching the throttle body. Match the throttle body to the manifold inlet: 105mm, 120mm or twin 103mm.

Dual-Injector LS Intake FAQ

What is the best dual-injector intake manifold for a turbo LS3?

For a rectangle-port LS3, L99 or L76, the Granatelli ZILLA is a billet dual-injector manifold with 16 injector ports, fuel rails included and a published 45 psi boost rating, available with a 105mm or 120mm inlet. The MEGAZILLA adds twin 103mm inlets for extreme builds.

Does the Holley 300-624 fit an LS3?

No. The Holley 300-624 and 300-625 Lo-Ram manifolds are for cathedral-port LS1/LS2/LS6 heads. Holley's rectangle-port dual-injector Lo-Ram base is the 300-683.

Will the ZILLA fit a cathedral-port LS1, LS6 or LQ4?

No. The ZILLA is designed for LS3-style rectangle-port heads. Call us before ordering for a cathedral-port build.

How much boost can the ZILLA handle?

The ZILLA and MEGAZILLA are rated to a maximum of 45 psi of boost.

Do I have to run 16 injectors?

No. Injector plugs are included so you can run 8, and you can fill all 16 ports later.

What injectors does the ZILLA use?

38mm LS3/LS7/LSA-style length injectors with LS3/LS7/LSA-style O-rings. Size them to your horsepower target and fuel type.

Are fuel rails included?

Yes. ZILLA fuel rails are included and set up for all 16 injectors.

Shop Granatelli Billet LS Intake Manifolds

See the full lineup in Granatelli Billet LS & LT Intake Manifolds, machined in Oxnard, California. Not sure which one fits your build? Call Granatelli Motor Sports at 1-805-486-6644, Monday–Friday, 8am–5pm PST.

Written by JoJo Granatelli — third generation at Granatelli Motor Sports in Oxnard, California, and the one who drives what the company builds. He set a quarter-mile record of 7.06 seconds at 157 mph at Famoso Dragstrip in August 2026. More about JoJo.