Muscle Mustangs & Fast FordsHow To Engine
Loading the Bullitt
It doesn't do much for a stocker, but swapping a Bullitt intake onto a blown 2-valve GT was worth mega horsepower.
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Everyone in the racing world knows about the benefits of using nitrous oxide or blowers to help boost the power of a given engine, but rarely do people think about the simple things such as rocker arms, ignition systems and even oil pans when using power adders.
Recently, we had a chance to swing over to LaRocca's Performance in Old Bridge, N.J., to check out some of its latest projects. One that caught our attention right away was a silver '99 35th Anniversary Mustang GT that was sitting on the chassis dyno in the back of the shop.
The car's owner, New Yorker Jimmy Vaccaro, was having the intake manifold replaced. The engine consisted of a stock 2-valve long-block that was helped along with a ProCharger F-3 supercharger. With some mild modifications, including a Lentech-prepared AOD transmission, the car had run in the 10.70s at close to 124 mph. Upon further inspection, we noticed a familiar looking intake manifold sitting on top of the engine--the hyped-up Ford Bullitt design.
"We scrapped the stock, plastic intake that comes on the 2-valve engines and replaced it with a Bullitt cast aluminum version," said Jimmy LaRocca of LaRocca's Performance. "We feel that with the improved runner design and better flowing throttle body, the car should pick up 20 or so horsepower."
The Bullitt intake design is a far cry from what most people in the Ford modular world are used to. While it had been in the Ford Racing catalog for a while, there wasn't a version that fit the '99-up Performance Improved cylinder heads. Ford fitted this intake to the 2001 Bullitt Mustang that was in part responsible for the engine's output being raised to 265 horsepower.
We were all curious to see what was involved in putting one of these setups on a standard 2-valve engine. We were also curious to see if the supercharger would help show the intake's true potential. LaRocca wrenches Jimmy Chahalis and Andrew Barrale performed the swap and explained to us that it wasn't as complicated as they had originally thought.
"The Bullitt intake kit that Vaccaro brought to us had everything that was needed to install it on the stock engine," said Barrale. "However, if you're installing this intake on a blown engine such as Vaccaro's, some custom work will have to be performed." Some of that custom work included repositioning the upper radiator hose, shimming the alternator bracket and modifying the throttle cable/transmission kickdown bracket.
"On a normally aspirated engine this intake is a virtual bolt-on, but when the car has a blower on it some modifications will have to be made," explained Barrale. "For one, the blower comes in contact with the upper radiator hose and, therefore, the hose will have to be relocated. You can replace the upper thermostat housing (with a Bullitt version) but the easier fix is to use a longer aftermarket radiator hose and reroute it away from the blower.
"The second problem is with the alternator bracket. Again, with the blower, the belt didn't want to line up correctly with the pulley, but the simple fix was to just shim the bracket with washers. On a normally aspirated engine this would not be a problem but the blower causes the bracket to have to be shimmed slightly in order for the belt to line up properly.
"The only other obstacle is the throttle cable. The Bullitt intake has a totally different throttle body arrangement but the kit does come with the proper bracket to make the switch. However, with the automatic kickdown cable [on the transmission] you will have to make a bracket to work with this arrangement. The Bullitt Mustang is only offered with a 5-speed gearbox, but this car has a Lentech AOD automatic transmission in it. We used an aftermarket cable from Lokar [available in the Summit Racing catalog] and that solved our problems."
Why Is The Bullitt Better? Like other tech stories, we would have loved to get some extra photos of the intake swap taking place, but it was pretty much done when we arrived at the shop. By looking at the photos, you can clearly see the differences in runner length and the intake construction.
"On a normally aspirated 2V engine, you won't see too much of a gain (when switching intakes) but on a blown application the advantages of using the Bullitt intake become huge," explained LaRocca. "For one, the runners are larger [on the Bullitt] but are not quite as long. You may wind up losing some torque on a normally aspirated combo but with the blower the shorter runner design definitely helps.
"The Bullitt intake, with its different runner design, works best in the 4000 to 6000 rpm range and that is where this blown combination spends most of its time. The stock unit has a very large runner configuration and is made from plastic, which can lose its strength under high boost situations. Also, the dual-plate throttle body flows smoother than the stock unit and helps distribute the boost into the engine more evenly."
Chahalis and Barrale removed the stock unit and bolted the Bullitt intake in place using a new set of factory intake gaskets. Then they swapped over the eight fuel injectors and the eight coil packs from the old intake to the new one. After filling up the engine with coolant, LaRocca headed over to the chassis dyno to see if their improvements would pay off.
They had made two pulls with the stock intake in place and the best numbers read 531.7 horsepower and 515.9 lbs.-ft. of torque. These are obviously impressive for a mostly stock 2V engine with nothing more than a ProCharger blower and a custom fuel system helping it along. Still, LaRocca and the boys were eager to see how much power the Bullitt intake might reward them with.
Within two pulls we had our answer. On the first run one of the tubes on the blower came loose, but the second hit revealed a jump to 566.1 horsepower and 520.2 lbs.-ft. of torque--that's a 34.4 horse jump and an extra 4.3 lbs.-ft. of torque at the wheels. "We figured that the intake would help some, say 20 hp, but none of us thought that it would reward us with quite that much power," said LaRocca.
All of the guy's were happy with their horsepower achievements but it was at nearby Old Bridge Township Raceway Park that the Bullitt intake really flexed its muscles. Vaccaro handed over the keys to LaRocca and he proceeded to blast down the quarter-mile in 10.32-seconds at a speed of 129 mph. (Remember, the previous best was in the 10.70s).
"The 35 extra horses were worth almost four-tenths on the track and, no doubt, the car could have run even faster yet," said LaRocca. "Because of the better flowing intake, we now think that the injectors are a little too small. What's even more impressive is that the car weighs a whopping 3690-lbs. With a little less weight and a bigger set of fuel injectors, we may be able to dip into the 9-second zone shortly."
As mentioned before the Bullitt intake doesn't seem to be quite as effective when bolted onto a normally aspirated engine combo, but it definitely works well with forced induction such as a blower or turbo. And this test also proves that, unlike with an expensive engine buildup or blower install, sometimes, big power gains can come in small packages.