"How long until it grenades?" Those five words started a string on turbomustangs.com that has lasted more than a year with 50,000 visits and more than 60 pages of replies. Marty Stromberger originally posted it when he decided to find out just how much boost a stock two-bolt Chevy short-block could take. So far, his '88 Firebird has made 703 hp at the wheels and runs 9.74 at 141 mph using the stock block and rotator and a set of iron heads.
The turbo idea was hatched on a road trip from Seattle to Spokane, Washington, when a thought occurred to Marty. The Buick Grand National works with a turbocharger and small-valve heads, so why not try it on a V-8? "I think the Buick is a great idea, but it is too heavy, has a six, and is not very aerodynamic," Marty says. He owned two '84 Turbo Buicks, so he knew that each of those turbos was capable of producing 375 hp each. He did the math and thought there might be a chance to hit 9.99 using two turbos and the right car. The search was on.
Marty's first score was a derelict '83 Firebird SE with a 2.8 and a five-speed from a small car lot for $387. "It drove home billowing blue smoke," Marty remembers. "But it needed everything and it was a V-6 car, so I decided to look for something else." That's when he found an '88 Firebird GTA that had been a weekend warrior/autocross car. It was cleaner than the SE and already had the V-8 parts. "I bought the GTA for $1,500 and a tailgate from a '70 Chevy truck," says Marty. "The car cost a lot more cash, but it belonged to a body man who had fixed all the little things that go wrong with the '80s throwaway cars."
Marty built the entire car himself. He learned his skills rebuilding transmissions at a garage called The Butcher Shop before moving to Tim's Hot Rod Fabrication to work for his father. He stayed there for 15 years, learning to fabricate for the street rod market. During that time, some of the big sellers at Barrett-Jackson came out of the diminutive shop a few miles east of the city. When that shop closed, Marty found a job at Shelley's Automotive, where the Firebird is beaten on its chassis dyno.
Originally, the Firebird was equipped with a 305 and a five-speed combo, with a scrawny catalytic converter welded to a massive Mufflex 4-inch exhaust system. "It sounded cool, but it ran like #@!*," says Marty. So he took the entire car apart and began to prepare it for 9-second travel. "I bought a header kit from Summit Racing and roughed out the exhaust. The A/C and the power steering had to go, but the rest of the power stuff stayed. I wanted to keep as much of it as I could." Under the car, Marty reinforced the subframe and moved the location of the torque-arm mount from the factory bracket on the transmission to the trans crossmember. "GM did that for noise and harshness, but it really should be attached to the crossmember," he says.
Marty knocked out the dings and painted the faded car black, Buick Grand National-style, and dropped in a freshly built four-bolt block with forged pistons, a steel crank, a set of Dart aluminum heads, and the twin GN turbochargers. The engine was on the transbrake at 12 psi when it exploded, taking out a couple of cylinder walls. Marty sleeved the engine and started again. "The repaired engine had a major overheating issue," says Marty. "One day it hit 260 degrees and cracked the deck, relieving the pressure and ending its life."
That's when Marty got his next great idea. The replacement motor had 150,000 miles on it and came from a guy who had been using it in his truck to commute for the last 60,000 miles. Marty was ready to get back to his junkyard roots with a little science experiment: How long until the used engine grenaded? Instead of rebuilding it, Marty just dropped it in including the original 991 truck heads with the 1.72/1.50 valves simply because they were free. "After all, the Buick GN was doing it with 1.71/1.50 valves; why not?" says Marty. That engine made 554 at the wheel on Shelley's Automotive dyno using two bone-stock '87 Grand National turbos that he bought used for $400. The only nonstock parts of the combo were 1.6:1 rockers and a Comp High Energy 268 cam swap. The small cam allowed him to pass emissions and get some tags to drive it on the street. "I got sick of trailer queens," he says.
At the strip the car ran 10.23 at 133 with 20-22 pounds of boost, and then Marty sprayed it with nitrous. "We couldn't kill it; it wouldn't die, so it needed nitrous." Using parts from a carbureted plate system, Marty plumbed a 90-shot about one foot before the throttle body. It made 616 at the wheel and hit 24 pounds of boost. At the track it carried the wheels and ran 9.75 at 141 mph. "What a good feeling," he says.
The combo was working well, so he brought out a set of 487X castings with 1.94/150 valves, changed out the springs, and did a quickie bowl blend before slapping them on the car, just to see what it would do. He pulled the pan and the mains and they looked just the way they did when he dropped the engine in, so he did nothing. By now the guys at turbomustangs.com were following along, and they donated a high-flow Edelbrock manifold base. Then Marty traded labor for a set of used aftermarket TE44 Buick turbos. On the dyno the car made 648 rwhp on the motor and then, with a 75 shot of nitrous, made 703. It also makes 700 lb-ft of torque, "and that's the fun part."
Who: Marty Stromberger, a hot rod car builder
What: A twin-turbo '88 Pontiac Firebird that is way faster than it should be
Where: Right outside of Spokane, Washington, in a small shop that looks kind of like a barn, we think. But we don't actually know what a working barn looks like.
Short-block: The block is a '76 two-bolt main from a work truck that was rebuilt with 0.040-over pistons, a sleeve in one cylinder, and a cast crank. The mains "squirm," as Marty says, with boost and nitrous at the same time but so far haven't come out of the block. It has a good used timing chain and a nice new oil pump.
Heads: The head gaskets are stock-bore, off-the-shelf $8 Corteco pieces. Marty thinks the secret to his success is not detonating the engine. "A lot of people are detonating and don't know it," he says. The first set of 991 cylinder-head castings received a fresh set of valvesprings and were decked so the head gaskets would last. Originally Marty didn't use screw-in rocker-arm studs. He paid for that when the exhaust stud popped and built so much pressure in the chamber that it pulled the intake stud when the rocker tried to open the valve. He had to repair that in the car. The 487X heads have (well, one of them) threaded studs and four new exhaust seats, and the other one is stock including the press-in studs and valve guides. Marty believes that the loose valve guides tighten up under the heat of the turbo. He also has a set of nice aluminum Dart heads, but he is afraid they will get damaged if the engine explodes.
Turbos: The small set of original TBO-348 Buick GN turbos were from the local Buick guy, Mike Dopkins. The next set were Precision Turbo TE44s, which are capable of 580 hp apiece. A nice roller cam, more intake, and good set of heads would help them reach their potential.
Wastegates: The 'gates are Turbonetics Evolutions and represent one of the few parts that Marty bought new. The blow-off valves are Turbonetics Raptors.
Fuel system: The fuel pump is an Aeromotive A1000 that is rated to 1,000 hp. A Barry Grant log-style fuel filter feeds with -8AN lines, and Marty used the stock feed as a return. If you look closely you can see that the stock fuel filter is still inline. The boost-referenced regulator is from Aeromotive. The nitrous system is also fed off the main pump, and the injectors are a Siemens Deka 55-pound high-impedance set.
Controls: The Holley Commander 950 is designed for fuel injection. It is a complete stand-alone that controls the fuel and spark curves from a laptop interface.
Exhaust: The headers are from a Summit weld-up header kit that Marty thinks was designed for Sprint cars with 131/44-inch primaries that neck down to a 211/42 into the turbo. From there, twin 3-inch downpipes feed into a single 4-inch pipe and a Dynatech 4-inch muffler. After reading up on sizing, Marty designed his system to handle 1,000 hp. His decision to run the smaller primaries (rather than 2-inch) helps to prevent lag. He also believes that bigger is better with secondary sizing; he's even seen 5-inch downpipes on the big 106mm turbos.
Intake: So far the intake is the original TPI except for a high-flow base and a 58mm BBK throttle body. He also reversed the fuel fittings to feed everything from the cooler firewall side of the motor.
Ignition: Marty only runs 22 degrees of total timing. He had to buy an MSD Digital 7 with a crank trigger but uses the gutted stock distributor to throw spark. An MSD digital window switch runs the nitrous. The plugs are standard Autolite 144s for street driving with 0.030-over to keep the spark from blowing out. "A heavy-hitter motor needs a smaller gap, no matter how much ignition you have."
Street fuel: Marty uses 91-octane on the street with 12 pounds of boost maximum. On race day, he uses 110-octane from a local gas station.
Nitrous: The kit is cobbled together from a Holley plate-style system. He welded a bung on the intake side and threaded in a Fogger2 nozzle for up to a 90-shot of nitrous.
Transmission: Once he yanked the original T5, he added a TH400 that he rebuilt backward and scattered. The second TH400 spit the case bushing out and lost fluid, killing both Second gear and the torque converter. The current TH400 has a BTE 10-inch, 2,200-rpm converter with TCI transbrake. So far it is holding together.
Rearend: Marty swapped the original Australian GM nine-bolt out the door in favor of a Ford 9-inch that was left over from a street rod build. He added Dutchman big-bearing ends and 31-spline axles. Marty is looking for a 35-spline differential. Got one?
Body: Marty is using the power windows and door locks every day. He laid the carpet and the paint himself.
Friends who helped: All the dyno tuning was performed at Shelley's Automotive. The limited machine work came from Jeff Cassell at Cassell Performance Engines. Guys who might get pissed if they don't see their names are his dad, Tim, who fired him last year, Mike Decaro, and Mike Dopkins.