Jerry Heasley
July 20, 2010

Our Lone Star Pony Car Saga Continues
Mark Scott's 1999 Mustang GT
Lots of things grow big in Texas, so we're told. certainly, one of those is Mark Scott's vehicle collection. Now, Mark certainly doesn't run one of those dusty, roadside tourist traps that combine a car 'museum' and mini-putt golf course. In fact, all his vehicles run and are exercised on the blacktop regularly. So here's a little puzzle. Mark has eight vehicles with a total of 32 cylinders and three turbochargers. what is the unique feature of his collection?

See, Mark is, by any definition, an enthusiast. Among the cars previously in his possession, he counts a 1965 Mustang, a 1976 Pontiac Trans-Am, an early-'70s Alfa Romeo, a Mitsubishi Starion Turbo and a Porsche 944. Still working on the puzzle? here's a hint-one of them is a Scott Flying Squirrel...does that help?

Anyway, a few years ago, when the New Edge Mustangs were first coming out, Mark fell in love with a chrome yellow GT convertible that was sitting at the local dealership. Once in his possession, Mark started making upgrade plans and eventually settled on installing a Vortech S-Trim supercharger. At that time, the 4.6 liter engine was only a few years new and there wasn't a well developed supply of performance parts. Before installing the blower, Mark's car spun the dyno rollers to the tune of 228 RWHP. This was quite a bit better than previous years' GTs, as 1999 saw the introduction of the PI (power improved) version of the 4.6 engine.

After installing the S-Trim, Mark saw the power jump to 310 on the rollers. In Mark's words, performance car tuning at the time "...was prehistoric by today's standards. The Vortech chip had a flat 10 degrees of timing all the time, with a ton of extra fuel." Mark thought he should be able to get more out of the engine and so he began to research alternatives. Soon enough, he had designed a new, custom intercooler for his car and had Spearco fabricate it for him. New piping was also justified, so he figured it out and had a local welder produce it for him. Along with a set of 36 lb. fuel injectors, Mark headed out to Dallas Mustangs to get a new dyno-based tune. his pioneering efforts were rewarded with 400 hard charging ponies at the rear wheels.

A couple of technical issues remained to be fixed - both the injectors and the MAF were at their respective limits and needed attention. Once those issues were behind him, the drop top Pony gained another 10 percent output. All of this work was still being built on top of the stock intake and internals of the engine. Mark took a break from the modifications scene, thinking he was done with the GT. we all know better than that, don't we?

In 2003, the bug bit again. Filling in his dance card this time were a built shortblock, massaged cylinder heads and a Bullitt intake conversion. The iron block now proudly holds a polished cobra steel crankshaft, Manley forged connecting rods with jE forged pistons helping to push the compression factor to 9.5. The SOhc cylinder heads were treated to porting, including removal of the swirl dams, along with a set of custom ground camshafts from comp cams. The Bullitt intake was ported and port matched to keep incoming air from the BBk throttle body marching along smoothly.

That combination took the GT to a whole new level, recording 530 RwhP and 445 RwTQ. Stout numbers, indeed. Unfortunately, what wasn't quite as stout was one of the valve guides that had found its way into a cylinder head. After about 3,000 miles of life experience, the guide decided to drop down into the cylinder itself. Luckily, not too much damage was done, but the motor had to come apart once more... and that, my friends, is where the real story begins.

As Mark tells the tale, he was then 'talked into' selling off the supercharger and switching to a turbo setup. Now, you and I both know how often any of us has to be 'talked into' doing some performance mods on our cars. More likely, Mark allowed himself to be talked into this, because it all felt pretty natural for him. why do we say that? well, you have to understand a little more about our Mr. Mark Scott from Austin, TX. Remember that collection of his? The one with eight vehicles and 32 cylinders? That's not because they're all 4-cylinder cars. Actually, there's one single cylinder example, a couple of twins, a 3-cylinder, plus a pair of 4-cylinders. Then, there's a couple of V8's, including the GT convertible featured here. So, six of the eight are motorcycles. There's also one more trick. See, two of those bikes are turbocharged, so that would be a power adder that Mark was already pretty familiar with.

Photo Gallery

View Photo Gallery

As a part owner of Victory of Austin, a Victory motorcycles dealership, Mark custom built a turbocharged Victory Vegas for his own use. The 1927 Scott Flying Squirrel is also one of the other bikes that fill his garage. Mark tells us that he's had three to four dozen other 'interesting' bikes pass through his hands over the years.

With that background, the whole turbo conversion idea seemed like a good one to Mark. Of course, the devil's in the details and there were a few to get through. For example, the convertible had previously been treated to a Maximium Motorsports' conversion, so getting the turbo plumbing to fit around their k-member led to many issues. Other MM pieces that made their way onto the car included the strut tower brace, lower A-arms and coilover conversion. Tokico 5-way adjustable shocks and struts and Global west rear lower control arms also round out the suspension work.

Eventually, Mark had custom turbo piping fabricated for the car, but somehow, the supplier didn't include any expansion joints, so cracks started showing up in less than a thousand miles. Mind you, when they took the car back to the dyno in February of last year, the results were pretty impressive. Using race gas, along with 24 psi of boost, the rollers showed 655 RwhP, along with 692 RWTQ.

Additional work to support the Garrett GT40 turbocharger included an upgrade to Bosch 55 lb. injectors, a Bell intercooler, dual cobra fuel pumps, a Fluidyne aluminum radiator and a SPEC Stage 3 clutch. having previously gone through a couple of stock transmissions, this convertible now sports a shiny Tremec T-56, 6-speed gearbox, Ford Racing aluminum driveshaft, 3.73 ratio gears and rear axle girdle.

The cracking issues with the plumbing, though, were an ongoing headache. Near the end of last year, Mark contacted Motion Dynamics in Austin to get some new tubes done up, including expansion joints. The challenges, Mark points out, are not insignificant. The "...area of a 3-inch diameter pipe is about 7 square inches. At 20 psi, the force separating the pipe is 140 lbs!" Additional work was needed to refine a few of the connections, but everything looks solid now - at least at 20 psi. At that boost level, the motive force logs in at 611/625 on race gas. In street trim, using 14 psi and pump gas, the story still remains fascinating at 531/567.

Back in the days of "only" 440 RwhP, Mark had visited River city Raceway in San Antonio and came back with a timeslip for 12.37 seconds at 118 mph. considering the power increase since that point, Mark figures the car is good for some low 11 second performances, perhaps even dipping into the high 10's. Problem is... that's not going to happen. Mark likes the 'vert without a roll bar and there's just no way the track is going to let him run those times without one. Mark's Ok with that, though, because he'd rather have his kids in the back seat, as he often does. "This really is a 'drive around town' car and not a race car. The stereo and A/c work great."

Looking back on the road he's taken to get here, Mark acknowledges that there have been a few speed bumps. "Doing your own development is expensive. Go ahead and buy off the shelf stuff that someone else has had the pain of developing. I have used injectors in sizes 30, 36, 40, 42, 48 and 55 pound, as well as four different MAFS and two intercoolers."

Given that Mark picked up this car just when the 4.6 liter PI engine came out, he may be a little hard on himself. "If I had decided what to do up front, I would have skipped the middle steps. But then, maybe it would not have been as much fun." Doubtless, Mark has had a lot of fun - and plenty of it to share with his kids. As nice as it may be, that's a lot harder to do with a turbocharged motorcycle. Mind you, once the kids go to bed...

Mark Scott's 1999 Mustang GT

Ford 4.6 liter SOHC V8

Engine Modifications
Ford cobra forged steel crankshaft, polished by Motion Dynamics, new iron cylinder block, ported OE cylinder heads, Bullitt intake manifold ported and port-matched by Motion Dynamics; BBk throttle body; Manley forged connecting rods; jE forged aluminum pistons; comp cams' custom ground camshaft; Innovative Turbo Systems' Multi-stage boost controller; Garrett GT40 Turbocharger; Fluidyne aluminum radiator; Bell intercoolers; Canton 8-qt sheet metal oil pan; Tweecer piggyback controller

Tremec T-56 six-speed manual transmission; FRPP aluminum driveshaft, 3.73 gears, rear axle girdle

Maximum Motorsports' Strut tower brace; kenny Brown Extreme Matrix subframe connectors; PBR 13" cross-drilled front brake rotors; Ford cobra brake calipers

Maximum Motorsports' caster/camber plates, k-member, A-arms, coilover conversion; Global West rear lower control arms; Tokico 5-way adjustable shock absorbers and struts

Wheels And Tires
Front: Kumho Ecsta Supra 275/40ZR17 tires on AFS chromed cobra R 17" x 9" wheels; Rear: Nitto 315/35R17 drag radials on AFS chromed cobra R 17" x 10.5" wheels

Cervini's Dual heat extractor hood

Corbeau seats; AutoMeter Phantom series gauges, including Vacuum/boost pressure, fuel pressure, oil pressure, exhaust gas temperature, dual channel intake temperature, fuel pressure, wideband O2 with datalogging

655 RWHP, 692 RWTQ @ 24 psi