Intake Manifolds & Parts

The intake manifold is the last, and arguably the most important, part of your engine’s air intake tract. It’s here where the air or air/fuel mixture that exits the throttle body or carburetor respectively is distributed to each individual cylinder head intake port. How well the intake flows and how evenly the air or air and fuel is allocated is critical to your engine’s power output and your vehicle’s performance.

On carbureted engines and fuel injected engines with Throttle Body Injection (TBI, also called single point injection), the intake air mixes with fuel as it enters the intake manifold. On multiport fuel injected engines, fuel is introduced to the intake air stream by individual fuel injectors located at the ends of the intake manifold runners. Newer engines with Gasoline Direct Injection (GDI) inject fuel right into the combustion chambers, so the intake manifold delivers only clean air to the cylinders on these engines. Cast iron or aluminum used to be the materials of choice for intake manifolds, but today most manifolds are made of plastic (technically a composite blend). Plastic is much lighter, so it helps in the quest for greater fuel efficiency, and it dissipates heat better than metal, so the intake air charge stays cooler for better combustion.

Many intake manifolds have an upper and lower half. The two halves and the intake manifold to cylinder head(s) junction are sealed with gaskets and secured with bolts. The carburetor or throttle body is attached to the intake manifold in the same manner. The integrity of the seal at these junctures is critical and all surfaces must be clean and smooth when new gaskets are installed to prevent air leaks that could cause a lean air/fuel mixture, rough idle, and poor performance. On many V engine designs the intake manifold also serves as the valley pan, and the ends of the manifold are sealed to the cylinder block. Care must be used here when gaskets are installed or oil leaks could result.

Some intake manifolds have coolant passages and incorporate the mount for the thermostat. On older V engines with carburetors or TBI, an exhaust crossover passage was cast into the intake manifold to heat the manifold and improve fuel vaporization when the engine is cold. Modern fuel injected engines are computer controlled and the computer depends on inputs from many sensors to regulate engine operation. An Engine Coolant Temperature (ECT) sensor may be mounted in an intake manifold coolant passage to provide a coolant temperature signal to the computer, and the air temperature in the intake manifold may be signaled to the computer by an Air Charge Temperature (ACT) sensor mounted in an intake manifold runner.

There are several reasons for dumping your factory intake for an aftermarket manifold: The runner shape on even performance models will generally not be as advanced as the latest aftermarket manifolds; The OE manifold may be constructed from heavy cast iron; if you have a V-type engine you may be able to get by without a heat crossover passage; and finally, the factory manifold’s configuration may be unsuited to the rest of your engine modifications. Even the best OE manifolds are a compromised result of drivability, emissions, underhood clearance, and above all cost considerations. Couple that with production line tolerances and you end up with a manifold with less than ideal runner bends and contours, and poor air flow and dispersion.

By switching to a state-of-the-art, lightweight, aluminum, performance manifold you’ll see an increase in horsepower and torque, and if you live in a warm climate and can do without the heat crossover, the cooler air/fuel mixture will increase power even further. An aftermarket performance intake manifold will help you get the most from your engine no matter the size or how it’s configured. Whether you have an in-line 4 or V8, torque monster or screaming high revver, we have the manifold to suit your needs. Factory manifolds were designed to work with the OE level of tune, with runners that are often narrow to keep velocity high at low rpm. But if you’ve changed the cam and cylinder heads, and carburetor or fuel injectors, you may want to make horsepower significantly higher up the rev band and that factory manifold’s not going to cut it.