IntakeHome | Free Mods | Intake | Ported Heads & Manifold | Exhaust | Gears | Transmission | Brakes | Parasitic HP | Fuelling | Interior | Weight | Performance | HP Gains | PartsThe stock intake system of the 5.0L V8 is highly restrictive so opening up this side of the engine to improve its ability to breathe in is the first step towards increasing its volumetric efficiency. The easiest approach to modifying the intake system on a stock 5.0 engine is to replace everything upstream of the intake manifold (air filter assembly, MAF sensor housing, airtube, and throttle body). The stock intake manifold is also restrictive at higher rpm but since a performance intake manifold should be matched to the cylinder heads and camshaft, intake manifold swaps are often performed together with the heads and cam (collectively known as the H/C/I). Indeed you can buy these as matched components in the Trick Flow, Holley Systemax, and Edelbrock upper engine kits. While it is necessary to get more air (and fuel) into the engine to improve its performance, that air must be as cool as possible (cool air contains more oxygen molecules) in order to derive the best performance gain (each 11*F increase in intake air temperature results in a 1% HP/TQ loss). While installing an air filter assembly that draws cooler air from the passenger side fenderwell is a step in the right direction, the stock intake manifold (and the air inside it) becomes very hot because it conducts heat from the cylinder heads. The upper intake manifold temperature can be reduced dramatically by installing a phenolic spacer between the upper and lower intake manifolds. This simple, inexpensive bolt-on modification not only increases the mass flow of the air entering the engine, but cooler air also reduces the engine's tendency to detonate thus allowing more ignition timing advance for further performance gains. This excellent tech article by Autospeed explains in more detail how intake manifold spacers work: Cool Stuff - Manifold Insulators Since the spacer increases the intake manifold runner length, it also produces a small gain in torque at low/medium engine speeds and shifts the torque peak to slightly lower rpm.
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C&L 76mm MAF Kit
The stock MAF sensor housing has a 72mm bore but a 19mm wide bar runs down the middle causing a major obstruction to airflow. The cross-sectional area is a mere 27.0 sq.cm. Porting the MAF sensor housing by cutting away the bar and grinding the cut edges smooth with a Dremel increases the cross-sectional area to 36.5 sq.cm and improves airflow by 35%. |
Ford Racing Intake Plenum Spacer Kit
I chose the Ford Racing 1/2" thick phenolic spacer (part no. M9486A51) for the stock EFI manifold. A 1" thick spacer is also available but raising the upper intake manifold this much can cause clearance problems with the factory strut tower brace. |
Summit Racing 75mm Throttle Body
The stock throttle body (bottom of photo) has a tiny 60mm bore (cross-sectional area is a pitiful 24.7 sq.cm) which restricts airflow at higher rpm. The low budget hotrodder can bore it out to 62mm but that only improves airflow by 7%. |