Tech Notes
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.