Tim Stockwell
July 1, 2005

When last we left off ("Lake Effect," June '05, p. 53), the Fox Lake P-51 Two-Valve modular intake manifold, designed for '99-'04 Mustang GTs, had strutted its stuff on the MD Motorsports in-house chassis dyno in our four-way intake manifold shootout. On Ken Bjonnes' all-out naturally aspirated Two-Valve race car, the manifold picked up 15 hp and 8 lb-ft of torque more than the Ford Bullitt intake manifold on the same car. Great results, no doubt, especially considering that almost no one else is even supporting the Two-Valve modular Mustang with a mass-production performance intake manifold. As a result of those numbers, and the constant urging of our readership, we're back at MD Motorsports to test how effective this intake manifold is on a more street-oriented combination-namely a stock GT with a Vortech supercharger.

As a review, Fox Lake had some lofty goals for the P-51 when design first began almost two years ago. The company tried to straighten and shorten the intake runners while equalizing airflow to each combustion chamber. This, of course, would greatly enhance the engine's efficiency. Ron Robart, owner of Fox Lake, also wanted to dramatically increase the horsepower of the Two-Valve engine combination without sacrificing any low-end power-something the GT is in short supply of anyway. The intake comes complete with all the hardware, and it will fit under the stock hood for $1,299.

The donor car for this test came from Glen Amos, an employee at Fox Lake. He borrowed his brother's Vortech-supercharged GT, headed to Cincinnati with a P-51 intake, and our boys at MD Motorsports did the rest. Honestly, we don't know if Glen's brother knows that his car is going to be in 5.0 Mustang & Super Fords magazine. But, we do appreciate him allowing us to mess with his car for a couple days.

The GT arrived with the standard Vortech kit already installed. The owner had also added a high-flow X-pipe, welded Flowmaster mufflers to the stock tailpipes, and placed a Trick Flow 4.6 Two-Valve intake elbow on the car. The test car was perfect except for that Trick Flow intake-a nice piece in and of itself, but we wanted a stocker versus P-51 data set. Ken Bjonnes and Brandon Alsept, owners of MD Motorsports, figured that the Trick Flow intake was worth about 10 hp and 10 lb-ft of torque at the wheels. So, please keep that in mind when you look at the numbers on the P-51.

Installation of the P-51, as we detailed in our first story on this intake last month, is somewhat involved. You will spend all of three hours swapping sensors, fuel rails, injectors, and miscellaneous bolts and accessories. Or, you can have MD Motorsports install one on your car for a small amount of money. Installed on our test car, boost remained at 8 psi and air/fuel numbers indicated the tune-up was safe for this combination. Ken and Brandon told us they could have gotten more aggressive with the P-51, but Glen was happy staying on the safe side of things (and, his brother probably didn't even know the car was missing).

On the chassis dyno at MD Motorsports, the GT kicked out 382.5 hp and 356.4 lb-ft after the install for a gain of 22.6 hp and 8.1 lb-ft at the wheels. Add in the power from the Trick Flow elbow, and it looks as if the P-51 would pick up the Two-Valve engine by close to 35 rwhp and 20 rwtq. As advertised, the torque numbers under the curve remained the same, so the P-51 won't kill bottom-end torque as would a race-oriented intake. Also note that at 3,500 rpm, the P-51 intake really shines with big power gains over the entire rpm range right up to 6,200 rpm. On the road, the guys reported perfect driveability with no indications the car had been touched until you got on it and reached the higher rpm range. There were no additional noises or power losses anywhere.