Dyno Tuning an LS1-Swap 1981 Malibu Wagon for 700 HP

This Malibu wagon’s goal was to create a tire-ripping, fun-time-having street car—a vehicle to fill with friends to rip burnouts around town and destroy cones on the autocross. After a year of trial and error, the LS1-swapped 1981 Malibu finally got on the chassis dyno; through 28 dyno pulls, the Malibu wagon was fine-tuned with Vortech’s standard, generic LS-swap kit and V1-Ti supercharger, picking up an additional 280 hp and 220 lb-ft.

Building the LS1…

A quick refresh on the project: It’s a gutted 1998 Trans Am Formula for its Gen-III LS1, then Pro Motor Engines in Mooresville, North Carolina, took a break from building wild NASCAR engines to help build the LS1-based 383ci stroker with a K1 crank, K1 rods, Wiseco dished pistons, and upgraded wrist pins.

The LS1 383 c.i. short-block is topped with Pro Motor Engine’s 243-casting heads, leftover from their Daytona Prototype program. They worked over the combustion chambers and installed Crower shaft-mounted rockers for some high-rpm stability. Pro Motor Engines builds a variety of different combustion chamber sizes, so we went with dished pistons resulting in 9:1 compression. The idea was that the lower compression would keep the engine happy and safe on pump gas.

Vortech’s Basic LS1 Kit

To accomplish the fun torque curve, the Vortech V1-Ti supercharger was added as a part of the LS-swap kit. The upgraded head unit is capable of 26 pounds of boost and 950 hp, enough to get to the previously claimed target of 800 crank horsepower. “With your size engine and combination, the dyno graph will just keep climbing, to a point,” said Jonathan Atkins, owner of Tick Performance in Mount Airy, North Carolina. “It’ll just keep making power as it keeps making boost.”

This basic non-intercooled kit includes a standard 6-inch crank pulley (PN: 4MA018-041) and 3.60-inch drive pulley (PN: 2A031-360; $111.99). With this combination on the low-compression LS1, it made between 5 and 7 pounds of boost; a 7.8-inch crank pulley (PN: 4MA018-061; $156.99) and 3.12-inch drive pulley (PN: 2A031-312; $11.99) were added to make some additional boost.

Dyno Tuning At Tick Performance

Jonathan used HP Tuners on the junkyard “411” GM ECU to dial-in the fueling, resulting in a best of 458 whp and 398 lb-ft of torque. On paper, the fuel system would be maxed out. With no intercooler, the intake air temps climbed from 135 degrees to 232 degrees Fahrenheit during a single run—it was played safe with 13 degrees of ignition timing. With E85 and more boost, the combination would make more power; it reached the maximum of the Holley 100-gph inline fuel pump, seeing as how the fuel pressure dropped off at high rpm.

Fuel System Upgrades

There was an upgrade from the Holley 100-gph inline pump (PN 12-890; $326.66) to a Holley VR-1 brushless fuel pump (PN 12-1500; $1,155), which will support more than 2,000 hp with gasoline and bolts in place of the old pump. Next, the experimental 70 lb/hr injectors from Advanced Fuel Dynamics were replaced with DeatschWerks 88 lb/hr injectors (PN 18U-01-0088-8; $619 set). These injectors flow 1,000 ccs at 40 psi, slightly bigger than the 750cc injectors. However, the pressure can be turned up on the more than ample pump to increase the flow if needed. “For street driving, using a smaller injector is beneficial,” Jonathan said. “It’s all a balancing act between the injectors and pump.” If injectors were installed too big, they would have difficulty fine-tuning the idle and partial throttle.

How To Build An LS-Swap G-Body Malibu

• Pick a 1978-1988 GM G-body intermediate for its light weight, low price, and parts availability. Did you know wagons are trending, and are super cheap right now?
• Build an early LS1 for its low cost, power potential, and parts availability.
• Toss the engine into the car. There’s plenty of room to fit an LS drivetrain into a G-body like this Malibu wagon.
• Get the stench out! If you want your family to ride with you without a round of tetanus shots, clean it up and fix the interior.
• Making big power with your LS-swap G-body? Improve the handling and braking.
• Upgrade the rear of the car in the handling, braking, and power department. A chain is only as strong as its weakest link.
• Don’t forget the fuel system. Cheat the checkbook with used NASCAR parts and a new way to boost power through E85 flexible fueling.
• It’s not necessary to do a high-dollar rack-and-pinion conversion.
• Add more room for tire clearance. These cars didn’t have a lot of power new, so they wore puny tires in small wheelwells.

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