With the lower manifold down, Greg installs the radical dual-plenum SSI upper intake. In addition to its wild appearance, the 75mm throttle-body opening and built-in EGR spacer are a couple of the other features on this intake that we think are cool. Notice the OEM valve covers are in place. The stock valve-cover bolts are too long for the Iron Eagle heads, so a shim is added to each bolt to make up the clearance difference and nix the possibility of experiencing a major oil leak. The throttle cable, PCV valve, vacuum hoses, and sensors are also reconnected once the upper intake is installed.
This plenum-cover gasket must be slipped in place before the cover is installed. Greg says mounting screws for the plate must be tightened evenly in a crisscross pattern to avoid a vacuum leak.
Since the factory thermostat housing on Greg's 5.0 had seen better days, we decided to upgrade with this clean 15-degree piece (PN 1066) from Performance Stainless Steel. The housing is made from CNC-machined 304 stainless and snugs up to the new manifold with the included Cometic gasket.
A fenderwell-mounted BBK cold-air system rounds out the upgrade components we're using on Greg's Pony. The high-flow conical air filter is in the fender, and air is channeled up through an 80mm C&L mass air housing that features a sampling tube sized for 24-lb/hr fuel injectors.
We reconvened back at Extreme Automotive shortly after Greg completed his H/C/I project. Our baseline numbers already had been recorded and stored in the dyno's computer. Saul "The Surgeon" Gutierrez is the resident dyno master and tuner at Extreme. After a quick timing (15 degrees advanced) and fuel pressure (32 psi) check, it's time to see how the parts perform.
Summit Racing's off-road X-shape crossover is a last-minute addition to our upgrade. The pipe arrived one day before our dyno appointment, so we bolted it on before making any pulls and gave the stock catalytics a well-earned rest.
On the Dyno
Here's proof that the H/C/I setup we came up with is no joke. Lead by Dart's Iron Eagle cast-iron cylinder heads and a supporting cast that includes an N-41 cam and intake/air-induction goodies from BBK Performance, Greg Montoya's pumped-up Pony gained a smooth 103 rwhp (peak to peak) with an additional 45 lb-ft of torque.
Greg's 'Stang is naturally aspirated, so we're fairly sure there's plenty of room for additional stout gains if a blower, turbo, or nitrous are added. A swap to Anderson's B-41 S/C cam, gears, bigger injectors, and a 90mm mass air will be necessary as well.
Besides the small total investment for the parts and the fact that this setup can be installed at home, the coolness is brought on by the fact that everything is compatible enough for the combination to make great power. On a stock-5.0 short-block, without any radical tuning other than setting timing and fuel pressure (no chips), we think the Dart/AFM/BBK H/C/I setup is a collection to consider for a stock-Fox performance upgrade.
Vlick here for the 1989 Mustang GT H/C/I dyno chart