Building an efficient drag-race engine around boost requires a little more math and planning than one might expect. To start, the engine builder may have to work within boundries established by the rulebook. But the primary goal is to match the boost potential of the power adder — whether that’s a supercharger or turbocharger — to the engine.
When the team behind the Power Automedia project vehicle known as BlownZmapped out an off-season rebuild agenda for both the chassis and powertrain, one primary goal was stepping up to a new ProChargerF1XR supercharger. Last year with driver James Lawrence, Blown Z won the NMCA West World Finals in 275 Drag Radial and finished third in the 2013 points chase. That engine was a 388ci LSX mated to a ProCharger F1X. Plans for the 2014 season call for improving on the team’s personal best run of 7.353 @ 190 mph and posing a consistent threat in NCMA Street Outlaw, PSCA Wild Street and WCHRA 275.
To that end over the winter break, Blown Z was treated to a stiffer chassis and roll cage, redesigned suspension and tranny upgrade (‘glide to a TH400). Late Model Engines(LME) of Houston, Texas, was also recruited to assemble a new LSX-based engine to complement the more potent F1XR.
“A big part of this build is maximizing the engine rpm level with that blower,” explains LME’s Bryan Neelen. “That was the point of building a 400-cubic-inch engine as opposed to a 427 or bigger. Each turbo or supercharger has efficiency range based on size of its turbine wheel. We worked to get this new supercharger in its peak efficiency at 9,500 to 9,700 rpm.”
This action plan stems from the premise that an internal combustion engine — in its most simplistic form — is an air pump. Filling the cylinders with all the available air-fuel mixture will result in the most efficient engine. Remember when NASCAR mandated restrictor plates for superspeedways? At the time, the reduced air charge cut horsepower in the 358 cubic-inch V8 engines from around 750 to 450. But some savvy engine builders lowered the displacement to around 300 to 320 ci and picked up horsepower with smaller engines! They were just matching the engine size to the available airflow and optimizing the engine’s efficiency. Such is the strategy LME assumed in determining Blown Z’s engine parameters.
“Instead of building a bigger engine and running out of air sooner, we go with a smaller engine that will allow more rpm,” says Neelen. “The goal of this engine was to turn more rpm than others in the class. When you’re turbo or supercharger limited, you adjust the displacement to help turn the rpm and still make power.”
Once all the decisions were finalized and parts ordered, the majority of build time focused on machine work and pre-assembly fitting and measuring. The cast-iron Chevy Performance LSX cylinder block secured from Pace Performance comes with numerous features to support high-boost and high-horsepower applications, but considerable work is still needed for optimum durability and sealing.