1993 Ford Cobra Mustang - Increasing Toxicity

With the lower manifold still on the car, crack loose the black heater line on the passenger side; then remove the intake manifold bolts and the lower manifold.

Make sure the cylinder-head surface is clean and free of any previous gasket material or silicone. Lay a towel or rag in the lifter valley to catch any debris as you clean. It doesn't hurt to rinse the lifter valley down afterwards with a new quart of cheap oil.

You'll need to swap over the heater tube, thermostat and housing, fuel rails, and injectors to the new lower manifold.

We ordered a set of Edelbrock gaskets for the intake manifold, and used silicone to seal the ends of the lifter valley.

The Performer RPM II intake manifold can accept up to a 75mm throttle body. Beyond that, you'll need to modify the manifold opening as shown here. We used the throttle body gasket to mark the opening, and then opened it using a carbide bit in a die grinder. Be careful not to break into the outside neck of the intake manifold.

After the rough opening was complete, Story went back with a sandpaper roll to smooth out the surface.

The modified opening is now finished. We would've liked to use the sandpaper roll on the rest of the intake, but we ran out of time.

The lower manifold is installed, and the fuel injectors and lines are reconnected.

One of the fitment issues we were worried about was the thermostat-housing to water-pump gap. We actually gained clearance with the new intake manifold, which is good, as we didn't want to have to grind on our trick Meziere water neck.

The upper plenum is fitted with the necessary vacuum fittings, and the plenum access plate is bolted on.

The Accufab throttle body and spacer is installed. The 80mm unit that we used is a race piece and doesn't have a provision for the valve cover vent. We remedied that with a simple breather cap from K&N Performance.

We topped off our 347ci bullet with 7 quarts of Royal Purple's 10W30 high-performance motor oil, which we've been using for some time. Whether at the dragstrip or on the road course, you won't have to worry about your engine's lubrication with this stuff coursing through its veins.

We were psyched to see that we gained 14 hp and 7 lb-ft torque with the Performer RPM II intake manifold. What's more impressive is that gains were seen just about everywhere in the rev range.