Muscle Mustangs & Fast Fords
Project 1993 Ford Mustang Cobra Gearset Install - Part 2 Increasing Toxicity
With Even More Horsepower And Torque From A Recent Intake-Manifold Change, Project Stolen Goods Gets A Steeper Gearset To See If We Can Drop Quarter-Mile Times.
Last month, you may have caught us testing a proposed theory on our resident '93 Cobra project car, Stolen Goods. The test, in fact, was nothing more than your average intake manifold swap. The theory was that a different manifold, namely the Edelbrock Performer RPM II, would pick up 20 or so horsepower, but lose 30 lb-ft in the process when bolted to our D.S.S. Racing 347ci engine. To our surprise, we picked up power and torque across the powerband.
Originally, we had picked out a torque-enhanced combination of induction parts for our Ford Racing Performance Parts (FRPP) Boss block-based 347 bullet, and it provided us with just that at 358 rwhp and 376 lb-ft of torque. The Edelbrock intake manifold produced 372 rwhp and 383 lb-ft of torque, with this sizeable gain seen across the entire rpm range. Peak power was still at a valvespring-friendly 5,800 rpm and change, and driveability seemed to increase with the new intake manifold.
Last month, we installed the intake and dyno-tested the Cobra. This month, we wanted to install a steeper gearset to see if we could reduce our elapsed time and put this snake into the 11s. First, however, we took it to the track to baseline it with the 3.55:1 ring-and-pinion ratio putting the power to the ground.
Project Stolen Goods was driven an hour and a half to Bradenton Motorsports Park in Bradenton, Florida, where we mounted our Mickey Thompson 275/40/17 drag radials. With the Flex-a-lite electric fan/radiator combo and our Meziere electric water pump circulating the coolant between rounds, we were able to make all of the passes at a relatively cool 160 degrees of coolant temperature.
Launching at 3,500 to get the feel for the track surface, the Cobra bogged slightly and took off with a 1.82 short time. The quarter-mile flashed by in 12.22 seconds at 114.02 mph. After our first pass out, we already eclipsed our previous best of 12.58 at 110 mph.
Seeing as how the track had considerable bite, we raised the launch rpm to 4,000. The transfer of energy loaded the clutch hard at the launch, and Stolen Goods leapt to a 1.80 60-foot time. We crossed the stripe in 12.12 seconds at 114.50 mph. The following run after that netted a 12.20 at 114.35 mph with a 1.81-second short time. We were pleased with the results thus far, but there was still time for one more go at the 1,320. We decided to raise the launch rpm further to 4,500 rpm, but by then, the track had gone away, and wheelspin abounded in First and Second gear. A 1.88 60-foot time followed by a 12.51 at 113 mph was the result. Still, we dropped over 0.4 second with the new intake manifold.
We were close to the 11-second zone, but hadn't hit it yet, so we put in a call to FRPP and ordered up a 4.30 ring-and-pinion gearset, along with a 31-spline Traction-Lok rear end. Steeper gears are usually a sure way to quicker elapsed times, and we thought the 4.30s should get the job done.
Until now, we'd been using the Torsen T-2R differential, but Torsen does not recommend performing clutch drops with this differential. We decided to pull it out before we caused serious damage to the rather costly unit, and swapped it out for the Traction-Lok. FRPP also provided us with an installation kit and a bottle of friction modifier to add to the differential fluid.
For the installation, we drove about five minutes down the road from our MM&FF Southern Command Center to Horsepower By Hermann (HBH), located in Tampa, Florida. Owner Hermann Stolzenburg has been in the Mustang business since the beginning and was even a contributor a time or two to MM&FF in its early days. The majority of HBH's business comes from word of mouth, so you know he has a good reputation for doing things properly. Plus, he's just a great guy to work with. Stolzenburg is in the process of relocating HBH back to Maryland, but we were able to get Stolen Goods booked in right before the move.
The 4.30 gear and differential swap were pretty straightforward, and he knocked it out in a few hours. We had also noticed that Stolen Goods' clutch pedal had tightened up recently and asked Stolzenburg to check its adjustment while the car was up in the air. We were using FRPP's adjustable cable, aluminum quadrant, and firewall adjuster at the time.
When the car was returned to us, we took it for a drive and were surprised to see that the 4.30s were remarkably easygoing on the street. With the Astro Performance 0.62 overdrive ratio in the transmission, that steep of a gear is completely livable on a daily basis, cruising at about 2,200 rpm at 55 mph. Once you begin to go faster than that, you'll see how fast the 4.30s accelerate the tach needle. If you live in a state where the normal highway speed limit is 55-60 mph, you should have no problem with the 4.30s. Here in Florida, we're used to 70-mph interstates and toll roads, so you may want to consider something a bit tamer if you plan on hitting the long drive.
We opted to trailer Stolen Goods to the track this time for the aforementioned cruise-rpm issue, and the fact that we were fully prepared to hammer it at the track. Since we didn't have to drive it, it was much easier to keep the car cool, and we iced down the intake and power pipe before each run.
Launching at 4,000 rpm and shifting at 6,400, we experienced wheelspin at the top of First gear, and our 60-foot time was a dismal 2.05 seconds. We crossed the finish line in 12.50 seconds at 114.03 mph. On our next hit, Stolen Goods hooked a bit better, knocking down the short time to a best-ever 1.74 seconds. We did tickle the rev limiter at the top of Third, but e.t. improved to a 12.17 at 113.23 mph.
Pass number three began with wheelspin at the top of First again, and a 1.78-second 60-foot time. This was followed by a 12.23 elapsed time at 113.76 mph. We also detected what we thought might be a bit of clutch slip during the 2-3 gear change. This was later confirmed on the return road when we rolled down the window and the smell of toasted clutch waffed in.
Attempt number four produced our best short time of the day at 1.70 seconds. The quarter-mile elapsed time checked in at 12.28 seconds at 112.65 mph. The lower speed was no doubt the result of us going through the traps on the rev limiter in Fourth gear. It seemed the 4.30s were a bit steep for the 26-inch tall Mickey Thompson tires we were using. To combat this on the next attempt, we opted to short-shift First at 5,800 rpm and shift each subsequent gear at 6,000 rpm.
Wheelspin at the top of First gear during attempt number five slowed the 60-foot time to 1.88 seconds, but the short-shifting worked down track as we improved slightly to a 12.26 at 114.86 mph. The mph was our fastest ever, so we knew things were headed in the right direction.
Until now, we hadn't been powershiting Stolen Goods, but we had to do something to get this Pony where it needed to be. For run number six, we launched the car at 4,000 rpm, and experienced wheelspin at the top of First once more, netting a 1.84 60-foot time. It seemed that as the car's weight transferred back forward after launch, it unloaded the tires too much, causing the wheelspin. Powershifting the Pony did help, though, as we clocked a 12.19 at 114.64 mph. Our last run of the day started with a 1.89 short time. This time, however, it wasn't wheelspin but clutch slip that we experienced at the top of First gear. The clutch did hold on each shift, but we could smell the dreaded brown dust after the run, and the engine compartment wreaked of it as well once we got back to the pits. Stolen Goods clocked a 12.36 at 114.14 mph.
With the slipping clutch and a pedal that didn't engage until it was nearly fully released, we decided to call it a day. We ordered a new clutch cable to try and get back to the track the following week, but it didn't arrive in time for our test and tune.
We had fallen short of our goal this time, but there's no doubt that, come wintertime, Stolen Goods will be an easy 11-second player. With its road-race suspension, it's not exactly dialed in for the quarter-mile, but we'll be installing Maximum Motorsport's torque arm in the near future, which the company says will improve traction both in a straight line and when coming out of the corners. Maybe it will be enough to get us in the 11s, even in the summer heat.
We'll be going back to the 3.55s, though, as we prep Stolen Goods for some track time at the SVTOA's high-performance driving event at Sebring International Raceway. We're pretty sure this won't be the last time Stolen Goods will see the dragstrip, but for now, it's time for some corner carving.