You can throw a camshaft, a carburetor, and plenty of other catalog parts at your small-block, but without some forethought-without a plan-your new motor is likely to be nothing more than a 120hp anchor that doesn't idle and spits raw gas out the headers.
Joe Alameddine is a man with a plan. He's an engineer with Dana Engine Controls and works in the company's research and development center, so developing and implementing plans is what fills his day-planner. Like many Detroit-area engineers, Joe is a dedicated car nut whose off-hours interests are hard to distinguish from his 9 to 5 routine. He's owned plenty of fast street cars over the years, and when he decided to boost the performance of his '96 Impala SS, he started with a plan.
So, with a stated project goal of, in his words, "1,000 horsepower on pump gas with a fuel efficiency of 20 mpg," it quickly became apparent that boosting his SS's horsepower was going to require some serious boost. Like, 23 pounds worth.
"A power adder was definitely going to be required," Alameddine says. "Turbocharging was selected because of the exemplary mass air quantity it produces, without sacrificing efficiency."
Of course, building a 1,000-horse small-block isn't as simple as plumbing a couple of hairdryers into the stock LT1's intake and exhaust systems. And with all that extra air coming into the engine, a few more cubic inches-for a total of 383-would help process it.
Another goal of the project was driveability. By topping the engine with an electronically controlled port fuel-injection system, Joe was able to do field development on his workplace project, Accel's new Calmap 2000 engine control software. (Dana owns Mr. Gasket Co., which owns Accel. Small world, huh?)
Ever the engineer, Joe outlined the engine's process for performance before a single main bearing cap was torqued down. That process included increasing the engine knock tolerance threshold (by creating a longer dwell time at TDC) to promote 94-octane friendliness, careful injector selection and timing with the Calmap 2000 software to improve emissions, maximize horsepower, and ensure driveability, and increasing the cylinders' volumetric efficiency with the intake manifold and combustion chamber designs.
Along with these process parameters, Joe was very careful with the selection of the turbos' compressor wheels, housings, and intercooler. And to improve the engine's overall efficiency, reflective and insulative thermal coating were to be used throughout the motor, turbos, exhaust, and intercooler.
The Bottom End
With the plan in hand, Joe turned to noted engine builder Brian Thomson and his Detroit shop, Thomson Automotive, for machining, balancing, and block blueprinting. Thomson has years of experience building race engines, as well as contracts with General Motors and Ford for engine development work. Thomson's in-house engine dyno would prove invaluable for sorting out many of the turbocharged engine's necessary tuning hurdles, too.
Starting with a four-bolt-main truck block (the two-bolt-main stock LT1 block was ditched), Thomson overbored it 0.030 inches and filled the holes with boost-friendly 8.9:1 forged pistons from JE. Attached to them are 6-inch Carrillo steel rods which, in turn, are attached to a Callies 3.75-inch-stroke crank. The piston crowns were coated with Swain Gold thermal material, which helps retain heat in the combustion chambers. The coating also allowed tighter clearances during assembly, because the pistons don't conduct as much heat and, therefore, expand less.
Because of the daily-driving goal for the engine, not to mention its relatively lofty 6,200-rpm rev range, Joe chose steel rods over lighter aluminum components. Another consideration was the tight tolerances needed throughout the engine to support the stresses of a highly pressurized engine. The longer, 6-inch rod length puts the pin closer to the piston crown, which reduces the pistons' tendency to rock within the bores.