Vortec Intake Manifold Guide: 5.7 & 305 Vortec Carb Conversion, Specs and Torque

Below: how to confirm you have Vortec heads, what a carb conversion really involves, which intake fits your build, and step-by-step installation.

1. Does your engine have Vortec heads?

• Count the intake bolts: Vortec heads use 8 (4 per side), close to vertical. Earlier small block heads use 12.
• Check the casting number: common L31 Vortec castings end in 906 or 062.
• Check the engine: the factory 5.7 Vortec (RPO L31), rated 255 hp @ 4,600 RPM and 330 lb-ft @ 2,800 RPM, came in most 1996–2002 GM trucks, SUVs and vans. The 5.0 Vortec (305) uses the same head pattern.

Why a standard SBC intake won't fit

Running Vortec heads on an older 350? The intake follows the heads, so you still need a Vortec intake.

2. What a 5.7 Vortec carb conversion needs

If only the factory injector assembly has failed, repairing it is often cheaper than converting. If you are going to a carburetor, plan for these:

• Fuel pressure: the factory pump runs about 60 psi; a carburetor needs 4–7 psi. Add a return-style regulator or a carburetor-pressure pump.
• Ignition: factory timing is computer-controlled. Use a distributor with mechanical and vacuum advance, or a standalone timing controller.
• Transmission: a 4L60E or 4L80E needs a standalone controller and a throttle position sensor on the carburetor. The speedometer may also depend on the computer.
• Water bypass: 1996+ Vortec blocks have no internal bypass. Run a 5/8 in. hose (about 7 in.) from the intake's front 3/8 NPT port to the 5/8 in. nipple on the passenger side of the water pump. On older blocks, plug the port.
• Choke: no exhaust-heated choke provision; use an electric or manual choke.
• Emissions: check your state's rules before removing factory fuel injection.

3. Which Vortec intake manifold to choose

Stock or towing truck: 2007 or 2116

Both make power from idle, which is what a stock 305 or 350 needs. Pick the 2007 for the lowest height and an included square-bore adapter; pick the 2116 if you want both carb types without an adapter.

Street performance: 2028 Air-Gap

With a bigger cam and headers, the Air-Gap runners stay away from the hot lifter valley for a cooler, denser charge up to 6,500 RPM.

High-RPM build: 2033

Single plane for 3,000–7,500 RPM. Not for stock trucks, and at 6.06 in. tall, check hood clearance first.

Carburetor tip: most street 350 Vortecs run well with a 600–750 CFM square-bore carburetor with an electric choke.

Every Haytalras Vortec intake is cast and CNC-machined in our own factory, and each unit is air-tightness, dimension and finish checked before it ships from our California or Georgia warehouse.

4. Parts you need

In the box: intake manifold, the needed bolts and plugs (2007 also includes the square-bore adapter set). Not included: intake gaskets.

• Vortec intake gasket set (OEM-style)
• Oil-resistant RTV, spray gasket adhesive, thread sealant
• 3/8 NPT to 5/8 hose fitting and 5/8 in. heater hose (water bypass)
• Carburetor studs, nuts and base gasket
• Thermostat housing and gasket (late-model water neck)
• Fuel line, regulator or pump, throttle linkage

5. Installation and torque specs

Step by step

1. Let the engine cool completely before removing the old intake.
2. Stuff rags into the ports and valley, scrape off all old gasket material, then wipe with lacquer thinner or alcohol.
3. If the heads or block were milled, the intake end surfaces may need machining to match.
4. Spray adhesive on the head side of each gasket and set it in place. No sealer on the intake gaskets.
5. Skip cork or rubber end seals: lay a 1/4 in. bead of RTV across each block rail, overlapping the gaskets at all four corners.
6. Lower the intake straight down, coat bolt threads with thread sealant and torque in sequence from the center out.
7. Plug unused water and vacuum ports, install the water bypass, then the distributor (fully engaged with the oil pump drive).
8. Run the engine about 30 minutes, let it cool, then re-torque.

Torque specs

6. FAQ

Will a Vortec intake fit a 305?

Yes. All four fit both the 5.0 (305) and 5.7 (350) Vortec.

What is the torque spec for a Vortec intake manifold?

12–15 lb-ft, center out, with thread sealant. Re-torque after the first 30-minute run once cooled.

Can I use a Vortec intake on an older block with Vortec heads?

Yes. Plug the front bypass port, because older blocks have an internal bypass.

Can I keep my factory fuel pump?

Only with a return-style regulator that drops pressure to carburetor level.

Is a 1987–1995 TBI 350 a Vortec?

No. It has 12 intake bolts with angled center bolts. See our SBC TBI vs 4-barrel intake guide.