1990 Ford Fox Mustang LS1 Dyno & Drag Test - The Orphan Part 4

Ever since we came up with the cockamamie idea to put an LS1 into a Fox Mustang, we've been having a tough time making new friends. Even now, four months into this project, we're sad to report that we have been universally considered outcasts from both the Chevy and Ford camps. But it's not surprising, really. These two marks and their followers have been at odds ever since Henry Ford was painting Model Ts black.

But do you really care what others think? We think you shouldn't-and let us tell you why. We have been in the car business long enough to realize that people will have opinions, but the only one that matters is yours. By installing a lightweight, easy-to-modify GM LS1 into a traction-friendly Fox Mustang, we have come up with one of the nastiest street cars you can build in your own garage. With careful project planning and budget management, we've only invested four months and a real-world budget of about $6,000 to build this car. And you can, too. The end result is a street/strip machine that stands out from the crowd, gets great fuel economy, benefits from modern technology and aftermarket support, and best of all, can trounce on just about any megabuck exotic car on the street.

As we mentioned earlier, we purchased used Internet goodies to enhance our otherwise stock LS1, but we weren't exactly sure of their origins. We do know that our cam specs in at 232/238-at-.050 with 592/.602 lift on a 112 LSA. We also know that the heads are CNC-ported 862 castings (61cc 5.3L truck heads), which bump compression up to about 11.0:1. They look really nice and work quite well, but since we didn't buy them ourselves, we can't speculate as to who might make or sell them. A ported stock throttle body connects to the stock LS6-style intake manifold, and a stock mass air meter with high-flow ends finishes up the go-fast hardware.

Dyno-miteWhen we first completed the car, we had a friend with an HP Tuner eliminate certain functions like VATS (Vehicle Anti-Theft System) and the rear oxygen sensors within the PCM. We did this just to get our Mustang running, and did not alter any of the fuel curves because we had no idea in which direction to go. To reduce the risk of engine damage, we didn't drive this thing too hard before heading to a tuner and a dyno. It was apparent that the mixture and timing curves were off, as the car surged with its modifications. Consequently, we knew a custom tune was in order.

To find a suitable late-model GM EFI tuner, we turned to Cartek Performance in Garwood, New Jersey. Over the years, it has specialized in tuning fuel-injected GM performance cars in the Northeast. The Cartek guys probably thought this Mustang made a wrong turn off the Garden State Parkway when it parked in front, but truth be told, they liked the swap, and thought it was pretty interesting. Well, maybe they were lying to make us feel better, but it felt good just the same.

Once strapped down onto the dyno, Cartek plugged a laptop into the OBD-II port to provide access to our PCM. Based on their experience with similar engines, they began manipulating the fuel and ignition tables with a base tune to establish power. Because our vehicle is not equipped with catalytic converters, Cartek tuned the car to run in open-loop mode all the time. [This means the tune-up will not have the ongoing benefit of oxygen-sensor feedback to automatically tweak the tune over time.-ed.]

On the first pull, injector duty cycle was at 98 percent, meaning the injectors were only closed 2 percent during max fuel consumption. The car made 402 hp at the wheels, but the air/fuel ratio was getting pretty darned lean at 13.4:1 on top, so Cartek recommended a switch to larger injectors. We went with MSD's 38 lb/hr high-impedance injectors (PN 2018), to get our injector duty cycle down and to increase our potential for more power and less detonation. The injectors dropped right in, and took only 30 minutes to replace. To play it safe, we then swapped out the stock ignition wires with a set of red MSD 8.5mm custom-fit cables designed for a Camaro Z28 (PN 32819). With these components in place, they reprogrammed the LS1 accordingly, and we were rewarded with 405 hp at 6,350 rpm, and 382 ft-lb of torque at 4,900 rpm at the wheels on Cartek's Dynojet. Just in case you were wondering, it was a pretty good day for air, as the shop's temperature was 70 degrees Fahrenheit and the barometric pressure was at a power-friendly 30.25 inches Hg. All things considered, our correction factor was 0.95.

Keeping Track-TionWith the car tuned and ready for a good old-fashioned beat down, we were set to step-up our game with some on-track drag testing. We pointed our Mustang toward Raceway Park in Englishtown, New Jersey, and were armed with slicks and skinnies. Dynos tend not to lie, but tracks always tell the truth.

The track had just reopened from a weeklong snow, which left it blanketed in white. Luckily, it was prepped and good to go on that glorious March morning. It was a brisk 50-degree day, and a mild 10-mph headwind made itself known. The track was prepared with VHT for sticky action, so we bolted up the 26x10 Mickey Thompsons to see what our multi-trick pony could do.

On its first pass, we were able to pull off an 11.261 at 122.79 mph. This was performed without power shifting, because our high-mileage T56 is rough. The synchros are a bit worn and thwarted the power shifting efforts on each upshift, but the short-time was promising. We witnessed a 1.573 with a 5,500-rpm launch.

On the second pass, we really tried to speed up the shift-but the tranny protested. Getting it into Third gear practically required two hands, and the car's performance suffered. The short-time was a 1.580, but we were staring at a timeslip that said 11.264 at 122.20 mph. If anything, it was consistent and repeatable.

On our third and final pass, we let the clutch drop at a higher 6,000 rpm, and the result was an astounding 1.511 60-foot time. But once we approached half-track and went for the 2-3 shift, the shift lever broke right off (that is, our makeshift weld on the shift handle failed, so don't trust us with your welding). The run was obviously aborted, and we coasted it onto the return road. We weren't able to improve our best ET of the day, but we didn't break anything major either, and the Orphan was happy about that.

Despite the broken shift handle, we were impressed with the first time out. The trap speed was indicative of excellent power, and made us feel that our goal of 10-second ETs is a true possibility (with some gearbox repairs to allow power shifting, and suspension tweaks to get the existing power to the ground).

Apples And Oranges Living TogetherWhen it was still powered by the iron-headed Ford 302, the car ran a best of 14.165 with a top trap speed of 94.99 mph. After our LS1 swap, we picked up 2.904 seconds in the quarter-mile and an incredible 27.8 mph. Equally impressive was the weight loss the Mustang experienced during its transformation. Despite the heavy T56 gearbox (compared to the original T5 five-speed), our LS1 Mustang now weighs in at 2,884 pounds without driver. It used to weigh 2,940 pounds-that's a substantial 56 pounds off the nose without any other changes.

Fuel economy prior to the LS1 conversion was about 19 mpg in combined city/highway driving with the 302. On the highway, we witnessed 21 mpg. With the LS1, we now average 22 mpg in mixed driving, and have measured as much as 29 mpg on the highway. Aside from the extra Overdrive gear, the LS1 has such a good fuel injection system that it's no surprise we picked up so much mileage.

In sum, the suspension still needs work, but we're happy with our numbers for now. Due to deadline restrictions, we were unable to get back to the track to achieve our 10-second goal on motor, but we did meet and exceed our fuel economy and driveability expectations. We'll keep you posted on whether our Orphan gets the respect it deserves, and if it can win over the hearts of all those it has touched.

The Proof's On The DynoOur little Orphan is running 11.20s and making great power, thanks to the mild head and cam package, and Cartek's tune. At just 3,500 rpm, this engine is flirting with the 350-ft-lb mark, and by 4,300 rpm, it's making more than 400 hp. With a hypothetical 15 percent drivetrain loss, our corrected peak of 414 hp and 390 ft-lb of torque at the rear wheels translates to 476 hp and 448 ft-lb at the crank.

As far as bang-for-the-buck goes, the LS1 is the engine of choice for custom swaps. Couple this potent engine with a lightweight Mustang, and you're looking at one of the most incredible power-to-weight ratios around. Divide the car's 2,884-pound weight (without driver) by the crankshaft power, and you come up with just 6.05 pounds for each horse to pull. That easily outdoes Chevy's benchmark of 6.21 for the current Z06 Corvette, and hands the Dodge Viper SRT10 its butt with its 510 horses, 3,380 curb weight, and 6.63 lb/hp ratio. On top of that, you can readily replicate this swap for less than $10,000, saving $60,000 to $70,000 in the process. It may not out- handle the dedicated sports cars in the twisties, but when the green light drops, it's all over for wannabe chumps-and with a car you built yourself.