Granatelli ZILLA 105mm vs. 120mm vs. MEGAZILLA Twin 103mm LS Intake Manifolds

Granatelli Motor Sports' billet LS intake manifold family gives builders three very different inlet strategies: a 105mm single inlet, a 120mm single inlet and the MEGAZILLA twin 103mm configuration. All three are machined from billet aluminum and made in the USA, and all three are listed for naturally aspirated, turbocharged and supercharged LS combinations.

The right manifold is not simply the one with the largest opening. It has to match the engine's airflow demand, the throttle body, the fuel system, hood clearance and what the car is actually built to do.

ZILLA vs. MEGAZILLA at a Glance

*Prices as of October 2026. Check the product page for current pricing and stock. Throttle bodies are sold separately.

ZILLA 105mm: The Serious Single-Inlet Package

The 105mm ZILLA gives you a large single throttle-body opening, a high-efficiency plenum and runner design and a straightforward single-throttle layout. It is the logical choice for high-performance combinations that need substantially more airflow than a factory-style intake but do not need the complexity of a giant inlet or a second throttle.

The black 980105 is listed for LS3-style rectangle-port engines: LS3, L99, LSA, L94, L76, L77, L96, L98, L92, L9H, LY6, LFA, LZ1, LS9 and LSX. Like every ZILLA, it is a dual-injection manifold with 16 injector ports, and it comes with injector plugs so you can run just 8 injectors, along with intake gaskets and the supplied installation components. The 980105S is the same 105mm inlet size in a silver finish at the same price.

Pair either one with the Granatelli 105mm drive-by-wire throttle body. The GMTBLS105 (natural) and GMTBLS105B (black) are CNC-machined from 6061-T6 billet aluminum, use the factory-style GM 6-pin drive-by-wire connector and are complete assemblies, so nothing moves over from your old throttle body.

ZILLA 120mm: Maximum Single-Inlet Airflow

The 120mm ZILLA increases inlet area for large-displacement, high-RPM and forced-induction LS combinations that have outgrown a 105mm opening. Granatelli Motor Sports builds the matching GMTBLS120 120mm drive-by-wire throttle body, so the manifold and throttle can be planned as one high-flow inlet system with the same 6-pin electronic throttle control. It shares the ZILLA dual-injection layout: 16 injector ports, with plugs supplied for an 8-injector setup.

Like the 105mm, the ZILLA 120mm is built for LS3-style rectangle-port heads, and its product page lists the direct-fit vehicles. Confirm fuel-system layout, hood clearance and throttle-body compatibility before ordering. A tune is required.

MEGAZILLA Twin 103mm: A Different Strategy

The MEGAZILLA is not a bigger single-inlet ZILLA. It uses two 103mm throttle-body inlets feeding a large high-flow plenum, built for extreme naturally aspirated engines and high-boost turbocharged and supercharged LS builds where a single throttle body has become the restriction. It fits the same LS3-style rectangle-port vehicles as the ZILLA (fitment tables on the 980103 page) and is rated to 45 psi of boost.

Two throttles means more of everything: induction piping, throttle linkage or electronic controls, accessory clearance and calibration work. Granatelli recommends professional installation and notes that additional fabrication, tuning and supporting components may be required. Plan it as a complete induction system, not a bolt-on.

How to Choose: Match the Manifold to the Engine

• Choose the ZILLA 105mm for a modified rectangle-port LS that needs more airflow than a factory-style intake, where you want a single 105mm throttle body and the option to run 8 injectors now and all 16 later.
• Choose the ZILLA 120mm when displacement, RPM or boost puts airflow demand beyond what a 105mm inlet supports and you can package the larger GMTBLS120 and its inlet tube.
• Choose the MEGAZILLA for large-displacement, high-RPM or heavily boosted competition builds where you have the budget, space and ECU strategy for twin throttle bodies.
• Running a Gen V LT instead? The ZILLA family is for LS engines. Granatelli Motor Sports offers the separate Billet Gen V LT Intake Manifold 980106 with a 105mm inlet ($2,375.00).

Bigger Is Not Always Faster

An oversized intake system on an engine that does not need the airflow can change velocity and throttle behavior without producing a useful power gain. Select the inlet size on engine demand and testing, not on the biggest number in the catalog. A 105mm ZILLA on the right combination will usually be easier to live with than a 120mm or twin-throttle setup on an engine that cannot use it.

Common Mistakes When Ordering

• Ordering by vehicle or displacement. Granatelli's fitment notices say not to buy any of these manifolds on year, model or engine size alone. Port style and bolt pattern decide fitment.
• Assuming cathedral-port heads will work. The 980105 is listed for rectangle-port engines. Confirm the head port style on every build, especially swaps.
• Forgetting the throttle body. The manifold does not include one. Budget for the matching 105mm, 120mm or twin 103mm throttle bodies.
• Buying or reusing fuel rails you do not need. Granatelli Motor Sports intake manifolds come with fuel rails. Dry-fit the rails and injectors before plumbing fuel lines.
• Measuring clearance on an engine stand. Check hood, cowl, firewall, brake booster and accessory clearance with the engine installed on its mounts.

Install and Tuning Notes

Use the gaskets and torque specifications from the installation instructions for your exact part number. Plan vacuum connections for the brake booster, PCV and MAP sensor before final assembly. Every one of these manifolds changes airflow and fueling, so have a qualified tuner calibrate the finished combination. On a boosted build, leak-check the assembled intake tract before a dyno session. If your ZILLA is going on a turbocharged LS, our guide to wastegates vs. blow-off valves covers the boost-control side of the same system.

More manifold questions are answered in our LS and LT Intake Manifold FAQ, and throttle-body sizing is covered in the Throttle Body FAQ. For a fitment check, call Granatelli Motor Sports at 1-805-486-6644, Monday to Friday, 8am to 5pm Pacific.

Frequently Asked Questions

Which throttle body fits the Granatelli ZILLA 105mm and 120mm manifolds?

Match the throttle body to the manifold inlet. The ZILLA 105mm pairs with the 105mm GMTBLS105 or GMTBLS105B, and the ZILLA 120mm pairs with the 120mm GMTBLS120. Both are drive-by-wire units that use the factory-style GM 6-pin connector.

Does the ZILLA intake manifold include a throttle body?

No. The throttle body is sold separately. ZILLA manifolds come with fuel rails and injector plugs for running 8 injectors, and the black 980105 also includes intake gaskets and the supplied installation components. Check the product listing for exactly what comes in the box.

Will a ZILLA manifold fit cathedral-port LS heads?

Do not assume it does. The ZILLA 980105 is listed for LS3-style rectangle-port engines such as the LS3, L99, LSA, L92, L76 and LS9. Confirm your cylinder-head port style before ordering.

Can I run only 8 injectors on a ZILLA intake manifold?

Yes. The ZILLA 980105, 980105S and 980120 are dual-injection manifolds with 16 injector ports, and they come with injector plugs so you can run 8 injectors. You can add the second set of 8 later if fuel demand calls for it.

What is the difference between the ZILLA and the MEGAZILLA?

The ZILLA uses a single throttle-body inlet, either 105mm or 120mm. The MEGAZILLA 980103 uses twin 103mm inlets feeding a large plenum and is intended for extreme naturally aspirated and high-boost LS builds. It needs more induction plumbing, throttle control and calibration work than a single-inlet ZILLA.

Can I run a ZILLA or MEGAZILLA on a turbo or supercharged LS?

Yes. Both are built for naturally aspirated, turbocharged and supercharged LS combinations and are rated to 45 psi of boost. Size the throttle body, injectors and fuel system to the build, and have it tuned.

Do I need a tune after installing a ZILLA or MEGAZILLA intake?

Yes. The ZILLA 980105S and 980120 listings state that a tune is required, and any of these manifolds changes airflow and fueling. Have a qualified tuner calibrate the complete combination.