Holley's 1974 Chevelle Wagon is a 10-Second Turbo Test Bed
If you were born in the 70's, you likely observed the roadside world through the windows of a station wagon. Before minivans and sport utility vehicles, the people mover of choice was a rolling bench-seat bungalow with more square inches of glass around the occupants than cubic inches under the hood. These suburban family appliances were long, low…and boring.
Hollywood cemented the station wagon's place in American pop culture with cameo appearances carrying rambunctious rug rats, snarky teenagers, and peeved parents down the highway to visit theme parks, eccentric relatives, and inevitable mechanical and mental breakdowns.
Pop culture nostalgia aside, the utility of the wagon can't be overlooked. Their generous interior proportions and versatile seating configurations make them great for hauling lots of humans and gear. Since many rear-wheel-drive wagon platforms are shared with some of our favorite muscle cars, wagons are low-hanging fruit for hot rodding.
Enthusiasts run the most successful firms in the automotive aftermarket industry, and Holley Performance Products is no exception. To demonstrate the possibilities of their wares, Holley chooses project vehicles that not only scratch their hot rodding itch, but serve as rolling testing laboratories for product concepts and promotion.
When Holley's Chief Gear Head, Tom Tomlinson, (OK, his official title is President and CEO) came across a 43,000-mile 1974 Chevelle wagon, he couldn't pass it up. "I love wagons and frequently search for them. This car from Colorado came up. It was super clean with low miles and had been decorated with some very hippy-style decals."
Where some overlooked the portly fuel-crises snoozer, squinting at the online auction photos, Tomlinson saw potential. Interest in GM's Gen III (LS) engines was catching fire, and Holley fueled the craze with swap-mined products to lower LS engine-swap barriers. The company needed a utilitarian, versatile test bed for products, and the A-body's quarry-sized engine compartment could accommodate virtually any engine combination. The Chevelle would make a great product development workhorse.
The original concept for the wagon was "Low Buck Long Roof." Planned as a budget-minded spit-shine with a mild drivetrain, the third-generation A-body needed a few subtle nips and tucks to give it a more muscular presence. Holley pulled the body off the frame and chucked the wheezy drivetrain. The frame and lowered suspension were powder coated, and a subtle brown and cream paint job was applied to the body. The bumpers were shortened to suck them tighter to the fenders, with the front piece gaining a lower opening.
Other than fresh carpet, the interior remains the same as when it lumbered off the assembly line. The straightforward theme continued under the hood, where a bone yard 6.0L LQ9 yanked from a wrecked truck replaced the Chevelle's smog-strangled small-block.
Holley topped the engine with their newly-developed dual-quad carburetor setup and a set of big block-inspired coil covers to motivate the wagon in groovy fashion. A set of Hooker cast iron manifolds for modern LS engines kept the exhaust system 70's simple. While the electronics were separated from the hydrocarbons, Holley's Dominator ECU was used to run the ignition and transmission control for the 4L60E transmission.
The wagon was completed for the 2011 Hot Rod Power Tour, where it ran respectable 14-second quarter-mile times and sipped less than a gallon of gas every twenty miles.
However, as turbocharging started to trickle down to street-driven LS swaps, Holley's offerings for the hair dryer faction grew from EFI systems to hard parts, including the company's turbo exhaust manifolds.
Holley's Engineering Manager, Tim Grillot, filled us in on the details. "We launched our new Hooker turbo manifolds and wanted a test and marketing vehicle. We already had the wagon with the LS and we thought it would be cool to breathe some new life into the wagon as it had been in the same basic configuration for a few years. We wanted to showcase how easy our LS turbo manifolds make it for a consumer to add a turbo to their LS vehicle. Our goal with the manifolds was to offer an elegant, easy solution to turbocharging. Historically, fabricating the turbo headers is the most challenging part to a turbo system. We tackled that challenge with this very affordable and easy solution. These manifolds, when combined with our crossover tube, are a direct, bolt-on fit for most popular chassis."
Grillot's recollection of workplace water cooler discussion led to a bench racing showdown. "Tom [Tomlinson] challenged me to make the wagon run high 11s at full weight with the stock 6.0 truck engine that was in the car." Grillot responded as only a logical drag racer could. Grillot scoffed and quickly stepped one lead foot confidently over Tomlinson's proverbial line in the sand, "Elevens? We'll run 10s with it."
While Grillot's ego confidently sauntered away to his office, a ticker tape of calculations trailed from the water cooler back to his desk. Reeling in the mental adding machine tape revealed a balance of red ink. Stock 6.0L engine…10:1 compression…4600 pounds. The horsepower side of the equation easily had four digits. Squeezing that kind of power out of a junkyard 6.0L engine—more than once—was a tall order. The odds of Grillot returning from the strip with a ten-second slip or a box of parts seemed about even.
Bluster aside, Grillot wasn't completely out of his element. He had built two 4.6L Ford-powered turbo cars: a stick shift 1965 Mustang that ran 10.80s on 17-inch street tires, and his 1978 Fairmont that ran 8.60 with a TH400 trans. Clearly, Grillot knew the "soft speed" potential of turbocharging.
Even though they planned to use the existing junkyard 6.0L engine, Holley knew the stock camshaft and valve springs wouldn't keep the necessary boost from lifting the valves. A Brian Tooley Racing Turbo Stage II cam and PAC valve springs replaced the stock components. The car's existing dual quad setup was replaced with a single-plane EFI manifold and 95mm throttle body.
Holley hung a 76mm Bullseye turbocharger off the company's aforementioned turbo manifold system, and dumped the spent exhaust out the front right corner. A 50mm Turbosmart wastegate keeps boost under control, and an eBay-sourced air-to-air intercooler chills the intake charge. All the intake and exhaust pluming was fabricated in-house in Holley's R&D facility.
A brushless Holley VR1 fuel pump feeds a steady supply of fuel to the Holley EFI injectors, rails, and fuel pressure regulator, and a Hughes-built 4L80E trans replaced the previous 4L60 unit. Grillot admits, "The torque converter is a little tight for an optimized drag vehicle, but this helps with street manors."
A 9-inch Ford axle with 3.70:1 gears rounds out the package. Holley uses two sets of wheels. On the street, the wagon rides on Circle Racing billet aluminum 18-inch wheels covered in 245/45 and 295/45 Nitto NT555 tires front and rear, respectively. The steelie lookalikes are swapped out for track duty with a set of Weld RT-S bead lock wheels measuring 15×10 holding 275/60-15 Mickey Thompson drag radials in the rear. The front rolls on Weld 17×4.5-inch Aluma Star 2.0 wheels and M/T Sportsman S/R 28 x 6 tires.
When making the required power on a stock engine with 10:1 compression, careful tuning is critical. Holley's Matt Lunsford programmed the Dominator EFI system and squeezed out 905 rear wheel horsepower on Holley's in-house Dynojet Dynamometer with the turbo shoving 19.5 PSI down the stock motor's throat. Peak power was at 5,800 RPM, and a stump-yanking 862 lb-ft of torque peaked at 5,300 RPM.
Big numbers aside, Grillot speaks glowingly of the Chevelle's streetabilty: "The car feels exactly how it looks on the street: super comfortable, stylish, and plush. It is truly a treat to drive. The car has A/C, power steering, and stock brakes, so it really drives like a stock 70's cruiser. The engine is very mild and coupled with the tunability of the Holley Dominator EFI system—that manages the engine, transmission, and all of the boost control—everything is very smooth and easy to drive."
But enough about street manners—did it run the number? At Holley's 2017 LS Fest in Bowling Green, Kentucky, it was time for Grillot to put up…or shut up. We were in attendance, and Grillot quipped: "Get your camera ready. I'm either going to run 10s in this thing or blow it up trying."
After filling strapping on his helmet and pulling the column shifter down into drive, Grillot headed to the burnout box. "There is no trans brake so it is a little hard to build boost on the starting line. As soon as it rolls out 30-60 feet the boost comes in hard and fast and it quickly starts making lots of steam! Before you know it you are sitting in what feels like grandma's station wagon, getting slammed in the back and quickly approaching speeds that seem unreasonable for the stock bench seat!"
How fast is unreasonable? How about a 10.89 at 130 MPH? The sub-11-second pass gained Grillot essential water cooler bragging rights…and a friendly reminder from the track that cars shouldn't run 10s with a stock interior.
Besides proving out the company's electronic fuel injection and exhaust components, what else did Holley learn? Grillot explains, "Turbos are an easy way to make LOTS of power!"
Holley doesn't plan any major changes to the car in the near future. "We're just going to drive it and have fun with it," Grillot muses. "The car will be taken on Power Tour and other shows. We'll continue to use it to showcase and develop new products. Just like any hot rodding project, it is a never-ending evolution."
Even though Grillot wheeled the car to the magic number, he's quick to credit Holley engineering lab technicians Lucas Embry and Logan Duvall who did all of the wrenching and assembly of the current setup on the wagon including the camshaft, turbo, fuel system, transmission swap, and all associated wiring.
By launching this two-ton barge into the 10s, this project raises more than eyebrows and expectations. It raises questions about the perceived limits of hot rodding…and the bidding prices of mid-70's A-body wagons.
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