Spectre Performance sent us...
Spectre Performance sent us this collection of components for our twin-inlet forced-induction system. The two inlets have 4-inch-diameter openings, and the housing is made of aluminum with a steel base. It includes a top-quality cotton-fiber filter element. Made to fit a 51/8-inch opening, the housing is PN 9869 and retails for $166.99. There are two lengths of flexible ducting, coded PN 9751, and each extends to a maximum of 41 inches in length. The cost of these is approximately $32.99 each. There's also a pair of duct mounting plates (left) that cost $4.99 each and are listed under PN 9148. These are intended to be used with openings made in the inner fender or radiator core support. There are also some worm gear clamps that are required to install the kit. These are made from stainless steel and sell for $7.99 a pair. Spectre also offers headlight funnel fixtures and even the wire screens for installations using the high-beam headlight openings, `a la the '64 Fairlane Thunderbolt-very cool.
Just prior to this story, our resident '67 Mustang had received a set of full-length headers. While headers helped the engine make power, they also increased underhood temperatures considerably. Those eight steel tubes radiated engine heat like mad, and we felt it every time we popped open the hood after a drive. It got us thinking about ways to ensure that the air getting to the engine was as cool as possible. We'd be seriously robbed of power if we didn't.
Our K-code-style open-element air cleaner sits between those super-heated headers, pulling that hot air into the carburetor. When we thought about some of the cold-air kits we've seen on newer Mustangs, we remembered that the air-cleaner element isn't situated on the top of the engine but far away from it on the inner fender. We really wanted to use a similar system that would harvest cooler, denser air in a location as far away as possible, so it wouldn't be affected as much by heat from the engine or exhaust components.
As die-hard Ford enthusiasts, we also thought it would be a neat idea to replicate a Thunderbolt-style arrangement wherein the air-cleaner enclosure is pressurized by twin inlet hoses force fed by the onrushing air. The faster the vehicle travels, the greater the ram-air effect, which in reality is actually a mild supercharged condition since inlet pressure is raised above natural volumetric efficiency.
We've known for a long time that a company called Spectre Performance offers some of the best induction hardware. One call to Spectre and we netted ourselves a single-plenum cold-air package, as well as the parts to design a Thunderbolt-style ram-air system. Our car is a Mustang, not a Fairlane, so we were curious to know how this induction setup looked and if we could make it work on our smaller car. We decided to create a mock-up and see what, if any, changes would have to be made. While digging around the Spectre Web site, we noticed the company even has prepackaged cold-air kits for late-model Mustangs (see the sidebar for more info).
Some S197 Love
The factory airbox on late-model Mustangs was designed for quiet operation as a high priority, so we knew there had to be some room for improvement. Ours is a stock '05 GT, and we used PN 9924, which is a complete cold-air kit for '05-and-newer V-8 Mustangs. The kit retails for $166.99, and Spectre says that it will improve horsepower, torque, and fuel economy. We decided to install this airbox onto our car and then see what the results were in all three of these categories.
We'd like to thank Bottle Blown Racing in Camarillo, California, for the labor and dyno testing for our story. We'll get figures for rear-wheel horsepower and torque, and then check on mileage improvements with our 200-mile drive home.
 |  Besides the twin-snorkel forced-induction...  Besides the twin-snorkel forced-induction system, Spectre also sent us this collection of components to make a single-inlet cold-air induction kit. We ordered these pieces after looking over the company's newly updated Web site. The single plenum we decided upon is listed as PN 9848 and costs $84.99. There are two straight, polished-aluminum tubing sections, PN 9179, at $13.99 a piece, and one 22-degree elbow, PN 9729, at $17.99. The filter support bracket (PN 9702) is listed at $26.99, while the alumuinum collars (PN 9706) sell for $8.99. The final element (excuse the pun), is of course the air filter, and the red cone piece seen here sells for $28.99. |  This shot of the cone-style...  This shot of the cone-style air-filter element shows the stepped opening, which allows it to be used on several different sizes of tubing. The filters are available in red, blue, black, yellow, and white. |
 Here we begin with the installation...  Here we begin with the installation of the plenum onto our Autolite four-barrel carburetor. The existing carburetor stud was just long enough, so it could be reused. |  The plenum is equipped with...  The plenum is equipped with a polished aluminum collar, and we tight-ened it down just a little. After the tubing is attached, the collar will then be securely fastened. |  Here we test fit the setup....  Here we test fit the setup. It's already evident that we won't need the second piece of straight tubing. With the plenum, connecting collars, and the filter element, it looks like we will have more than enough length of piping. |
 The junction collars are high...  The junction collars are high quality in their construction and have a bead running around the inside of the rubber seal to ensure a leakproof connection when tightened. |  We decided to add this support...  We decided to add this support collar to the arrangement, as it will make for a sturdier installation. The collar will be seated in the filter base, and the worm clamp will be secured. |  Sometimes things work out...  Sometimes things work out just right-we discovered that we could attach the filter support to the inner fender using an existing hole. |