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December 13, 2022
THE AUTO BUILDER
Featured
628HP LS7X BUILD
Some of the greatest feelings in life come with a rise in rpm, a dropped clutch and tests of traction stretching the boundaries of our physiology. These are the emotions many of us cherish, and while many factors can evoke such emotions, the single most influential force behind these kinetic kicks is torque (which is then equated into horsepower).
PRODUCT SPOTLIGHT: Slant-Edge 100 Amp Alternators by Factory PerformanceTM Parts
In the world of high-performance builds, attention to detail sets great cars apart from the rest. That’s why Factory Performance™ Parts, a division of PROFORM® Parts, has taken a fresh approach to a time-tested workhorse with the launch of the new Slant-Edge 100 Amp Alternators—a stylish, high-output evolution of the iconic GM 10SI. Designed for those who care as much about what’s under the hood as how it looks when the hood is up, the Slant-Edge delivers form and function in equal measure.
GOODGUYS COLUMBUS 2007
Over the last several years, the Goodguys PPG Nationals in Columbus, Ohio, has established itself as one of the nation’s premier hot rodding events. This event, along with the Detroit Autorama and a few others, has proven to be one of the main events at which builders choose to debut new cars, and trophies are as hotly contested here as at any show in the country. But Columbus is about more than just trophies—it’s about bringing your own car, no matter what kind of shape it’s in, to hang out with the owners of the other 6,000 vehicles that will be there, and to have fun at Goodguys’ premier event.
Spotlighter
TEST AND TUNE
It’s a Constant Battle, But This Turbocharged Trans Am Just Keeps Getting Faster
A stroll through the pits at the local 1/8-mile dragstrip is always fun for us, as you’re likely to see any number of cars that use a full-tube chassis, fiberglass body and monstrous slicks to click off consistent 5-second elapsed 1/8-mile times. However, it’s far more entertaining to see a stock-appearing car hit those same numbers, and that’s exactly what Greg Corbin’s ’98 Trans Am is capable of doing.
Author
Tommy Lee Byrd
Words & Photography
Always Tinkering for More Speed
In traditional drag-racing fashion, Corbin just can’t get enough of it, so he’s always working on ways to make his Pontiac faster, whether it means minor tuning or a substantial change in the setup. He’s a gearhead, which means he’ll never really be content with his car’s performance, no matter how fast it goes, but for the time being, his car is at a level most street cars will never reach.
The Evolution of Corbin’s Trans Am
Like many car guys, Corbin didn’t plan to build his Trans Am to this extent, but that’s part of the car hobby. Originally, plans called for a small dose of nitrous oxide, but that was child’s play compared to the car you see here. Now it boasts over 1,000 hp at the wheels, as the 88mm Precision turbocharger screams, and the hefty Poncho flies down the 1/8-mile in 6 seconds flat at 118 mph—and that’s nowhere near full boost. And just because it runs insanely fast and proves to be reliable, Corbin is fast working on it so that it will run deep into the 5-second zone, and judging from that big mph he ran on the 6-flat pass, the 5’s are but an experience away.
Chevrolet Power in a Pontiac Package
Though it wears Pontiac badges, the power is purely Chevrolet, as a Gen III small block is the motivation of choice. The original LS1 from this Trans Am wouldn’t hold up to the extreme abuse from such a huge turbocharger, so the obvious choice was a 6.0-liter short block, from Weber Racing Equipment in North Ridgeville, Ohio. Capable of holding 1,500 hp, the stock crankshaft is in place, but the block is packed with Wiseco forged pistons and Carrillo K1 rods for durability. The dished pistons provide an 8.3:1 compression ratio, which is perfect for a boosted application like this one, and the additional 0.030-inch piston diameter brings the displacement up to 370 ci.
Maximizing Airflow and Fuel Delivery
Airflow is a major part of making a turbocharged engine perform to its maximum capability, and Airflow Research offers an awesome line of heads for the LS family of engines. The “Mongoose” heads feature 225cc intake runners, 2.08- and 1.60-inch valves and 72cc combustion chambers right out of the box, so they needed minimal work to be perfect for Corbin’s engine before sliding over the ARP studs. Corbin calls upon a custom aluminum fuel cell, a MagnaFuel pump and a collection of Precision 95-pound injectors to supply fuel, while a FAST XFI fuel management system controls exactly how much of it to use. Even with all of these go-fast components, the stock ignition is in place and an LS6 intake manifold does a great job of dispersing fuel and air into the ports.
Precision Turbo Power
Just in front of the bulletproof engine is the heart of all this power—a Precision 88mm turbocharger, fitted with large-diameter piping and a big air-to-air intercooler that keeps the intake charge cool and allows for additional boost. From the turbocharger, the 4-inch exhaust has a short route to travel, as it exits through the front bumper just in front of the passenger-side front wheel.
Transmission and Rearend Setup
Moving rearward, a Glenn McCary-built TH400 automatic transmission sends power to the rearend through a PTC 5,000-rpm stall converter, while Corbin shifts with a Hurst Quarter-Stick. Out back, a Moser 12-bolt rear rides on a torque-arm setup, equipped with stock springs and Competition Engineering shocks. Inside the housing is a full spool, a 3.42 gear set and a couple of 35-spline axles to withstand the sudden shock of a boosted trans-brake launch. An adjustable Daffron Race Innovations Panhard bar keeps horizontal rearend movement to a minimum, while the DRI lower control arms offer adjustability and added strength over the stock units. For traction, Corbin used a pair of Mickey Thompson 28×10.5-inch slicks, wrapped around Bogart D-10 wheels that measure 15×9.75 inches. Up front, you’ll find a matching pair of Bogarts, measuring 15×4 inches, with a set of lightweight Strange drag brakes hiding behind the spokes.
Chassis and Suspension Improvements
For additional weight savings, Corbin installed a BMR tubular K-member, which mounts a complete BMR front suspension. For better weight transfer, as well as softer landings from wheels-up launches, Corbin calls upon a pair of QA1 coilovers, fitted with Eibach drag springs, while a Flaming River manual rack keeps the steering system simple and effective. The weight savings continues inside with a pair of Kirkey aluminum race seats, which are fitted with five-point harnesses to keep Corbin restrained, while a Wolfe Race Craft 10-point rollcage adds weight, but also adds safety for this 1,000hp machine.
Record Runs and Future Goals
Considering the 6.08-second elapsed times he ran at Brainerd Optimist 1/8-mile dragstrip, Corbin’s Trans Am is sure to run in the 8’s off the trailer in the 1/4-mile. His recorded runs from the 1/8-mile started with a 6.60 on nearly no boost, before dropping to a 6.36, then down a full tenth, to a 6.24. Times went down again to a 6.08, but that was a low-boost run to combat a slippery track. He plans for 1/8-mile times in the 5.50 range when the track can hold it. And with 22 psi of boost, that will certainly be a possibility, which means mid-8’s in the 1/4 will come soon enough. Low-boost launches are the norm for now, but plans are to up the boost and hope the rear bumper doesn’t get damaged in the process.
A True Dragstrip Machine
And though Corbin’s car may not be as street-friendly as other late-model muscle cars, it’s no slouch at the dragstrip, and it helps prove that the LS line of engines is perfect for this kind of abuse, when aptly equipped. At the track, Sam Daffron from DRI is busy on the laptop, tuning the wicked 370ci engine to perfection, which is a huge part of getting it down the track in the quickest possible manner, according to conditions.
We look forward to seeing just how fast this Trans Am will go, but for now, we commend Corbin for running 6-flat in the 1/8-mile, as that is an awesome accomplishment for any street car. While more testing and tuning is in order, that’s the fun part, which Corbin can certainly attest to.
Under the ram-air hood, there’s no shortage of go-fast goodies, including the big power-adder—a Precision 88mm turbocharger. The turbo is fitted with large piping, an air-to-air intercooler and a JGS wastegate. Sam Daffron from Daffron Race Innovations is constantly tweaking the setup with the FAST XFI ECU, and Corbin keeps chopping down the ETs.
For strength and durability under large amounts of boost, Corbin chose a 6.0-liter short block from Weber Racing Equipment. The block is topped with a pair of AFR 225 Mongoose cylinder heads that produce an 8.3:1 compression ratio in combination with the Wiseco forged pistons and pull air from the LS6 intake manifold. A Griffin radiator keeps the 1,000hp engine cool.
Inside Corbin’s Trans Am is a nice blend of racecar stark and original equipment. Stock door panels, carpet and console keep it simple, while the aluminum Kirkey seats, Simpson racing harnesses and Wolfe Race Craft 10-point rollcage keep the cockpit safe.
Check out the detachable Grant steering wheel, which has buttons for the trans brake and Hurst roll control.
A host of Auto Meter gauges rides in the dash and custom heater and radio-delete panel, to keep Corbin informed as to his turbocharged engine’s vital signs. An Auto Meter tachometer hangs from the rollcage, while the FAST XFI/XIM
equipment is mounted to the glovebox and a FAST air/fuel meter sticks to the windshield.
Out back, a Moser 12-bolt rearend holds a 3.42 gear set and 35-spline axles, and mounts to a torque-arm suspension, damped by stock springs and Competition Engineering shocks. The body on Corbin’s Trans Am is very stock, and you’d never know this car was capable of 5-second 1/8-mile elapsed times if it weren’t for the mandatory parachute.
