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Here's Why the Quad 4 Was One of GM's Most Important Engines Ever

What GM came up with was the first ever entirely GM-designed dual overhead camshaft, four valve-per-cylinder inline-four engine called the Quad 4, a small powertrain that the company advertised offered the power of a V8 but with much more efficiency. The General considered it a “milestone in engine design,” and in many ways, it was for GM.

Starting with its debut in 1987 in the Oldsmobile Cutlass Calais GT, this transverse-mounted motor and its derivatives would become some of the most ubiquitous small-car powerplants in the U.S., finding their way into front-wheel drive Oldsmobiles, Buicks, Pontiacs, and Chevrolets throughout the entirety of the ’90s before being replaced in 2000 by a 2.2-liter Ecotec“Global Four Cylinder” engine, which is part of a line of many generations of engine architectures holding the Ecotec name including ones in use today.

The Quad 4 Made a Lot of Power for Its Size

The Quad 4 was a chain-driven, dual overhead cam, four valve per cylinder four cylinder engine with an iron block and aluminum cylinder head, as well as aluminum parts like the oil pan, timing chain housing, and camshaft carriers

The 2.3-liter motor has a 92 mm bore and a 85 mm stroke, making it an oversquare design. The compression ratio is 9.5 to one, the lifters are hydraulic, and the fuel is delivered via electronic fuel injection, as had become fairly common by the late 1980s.

One of the features that made the Quad 4 different was its distributor-less and wireless ignition system, the basic idea of which has since become the standard for pretty much all gasoline cars. Saab also offered a similar system at around the same time, but it would have looked wild to American car traditionalists, opening their hood and wondering where the wires had gone.

Instead of a camshaft-driven distributor and spark plug wires as was traditional on most engines from the beginning of car-dom through the 1980s, and even into the 2000s, the Quad 4 used a system called “direct-fire.” Relying on timing information from a crankshaft position sensor, the setup put an ignition module and two ignition coils directly above the cylinder head, and covered it all with a nice aluminum cover adorned with the text “QUAD 4.” It is this die-cast aluminum cover, with its many horizontal “fins,” that makes the Quad 4 so distinguishable in the engine bays of mid-size GM products of the era.

Oldsmobile’s chief engineer Ted Louckes showed the benefits of the wireless integrated direct ignition found on top of the Quad 4 in a presentation to journalists in December of 1985, displaying a graphic that mentioned better heat sinking, reduced sensitivity to spark plug fouling, better arc protection, better corrosion resistance, better protection against interference, and just fewer failure modes in general.

Power output for the Quad 4 was 150 horsepower at 5,200 RPM and torque was 160 lb-ft at 4,000 RPM, with GM saying 80 percent of that twist was available at idle. Redline was listed as between 6,800 and 7,000 RPM.

This was a fairly high-revving motor at the time, and the power output was, at least compared to the rest of GM’s line, spectacular for its size, with GM touting 1.07 horsepower per cubic inch.

And the 1.30 HP/cubic inch figure of the 180 horsepower “High Output” Quad 4 (which we’ll talk about in a sec), was considered an industry benchmark for naturally aspirated engines, with some even using it as a yard stick of comparison for brutes like the Acura NSX and Ford Taurus SHO.

Just look at the other engines that were available in Oldsmobiles in 1988:

Notice that the 2.5-liter four cylinder and the 3.0-liter V6 offered in the Cutlass Calais make less power and torque than the 2.3-liter Quad 4 despite their higher displacements. Looking at the engines in the other vehicles shows that the Quad 4 outshined the 2.8-liter offered in the Cutlass Cierra and Cutlass Supreme in terms of power, and even matched the Cutlass Cierra’s big 3.8-liter’s horsepower output.

The engine was a big step toward bringing GM’s engine line into modernity, with Louckes saying the prototypes of the Quad 4 “provided [GM] with more knowledge and data than any previous engine program at General Motors.”

I spoke with Andy Randolph, the technical director at ECR Engines—a NASCAR engine developer based out of Welcome, North Carolina—and someone with decades of experience working on powertrains, including at General Motors in the 1980s. He told me a bit about what this engine meant to GM:

There were several state-of-the-art features incorporated into the engine, although since then much has been learned about DOHC engine design (particularly valve train) that enables higher power and lower friction. The Quad 4 engine was a game changer for GM in that it was an acknowledgement that higher-cost engine features can be beneficial in some applications. This opened the door for inclusion of greater technology (and higher cost) in many engines to follow.

The Engine Set a World Speed Record Before It Even Launched

The Quad 4 didn’t hit dealerships until 1987, but plans to market the it in the most spectacular way possible began way back in 1984. That’s when GM decided to build an incredible, Quad 4-powered high performance machine that would later be piloted by four-time Indy 500 winner and just all-around racing legend, A.J. Foyt in an attempt at a high-speed record.

The sleek sports car was called the Oldsmobile Aerotech, and it was developed specifically to show what the Quad 4 engine was capable of. The car’s striking design was first penned by legendary stylist who would later become GM’s VP of Global Design, Ed Welburn. It was a single seater whose architecture was based on a 1984 March Engineering Indy race car chassis that GM had bought from A.J. Foyt, its body was made largely of carbon fiber, and it featured a head-up display.

(That last bit is interesting because many consider the first ever production head-up display to have been introduced in the 1988 Oldsmobile Cutlass Supreme Indy 500 Pace car edition, of which only 50 were made. These cars were based on the real ’88 Indy 500 pace car, which featured a specially-tuned 250 horsepower turbocharged Quad 4 that was promised but never released. Incidentally, the car was piloted by Chuck Yeager.)

Actually, there were three Aerotechs built, two called the short tail and one called a long tail. Using one of the short tails equipped with a 900 horsepower“RE” version of the Quad 4, in August of 1987 at a test track in Fort Stockton, Texas, A.J. Foyte managed a 257.123 mph closed-course speed record, besting the previous 250.918 mph record set in 1979 by a V8 Mercedes. In addition, in the long tail car with a “BE” version of the Quad 4 making 1,000 horsepower, he reached 267.399 mph in a “flying mile,” also claiming the world record.

Despite the publicity stunt, the “BE” and “RE” engines, developed by California-based company Fueling Engineering and Michigan-based Batten engineering, respectively, were actually quite different than the Quad 4 that would make its way into GM N-Body and W-Body passenger cars of the ’80s and ’90s. For one, they were both turbocharged, with the 900 horsepower RE receiving a single turbo, and the 1,000 horsepower BE getting a set of twins.

To handle the nearly 60 psi of boost, the “Super Heavy Duty” versions of the Quad 4 were 2.0-liter engines instead of of 2.3s. This, Oldmobile’s chief engineer Ted Louckes said, gave the engines thicker walls. Those walls were part of an aluminum block instead of the iron one on the production Quad 4, though they included iron sleeves, as well as a deck plate and other reinforcements, since the engines were stressed member’s of the Aerotech’s chassis.

They also had unique internal hardware like pistons, rods and cranks, plus different cylinder heads, special intake and exhaust setups, adjustable solid lifters instead of hydraulic ones, a special fuel injection system, and a solid state ignition system meant to work up to 12,000 RPM.

So really, these Aerotech motors weren’t truly Quad 4s, but as Oldsmobile puts it in its press release about the record-setting cars, the engines were “architecturally identical.” This means they had the same 100 mm bore centers as the production engine, and they used the same dual overhead cam setup with four valves per cylinder. The RE model—and perhaps even the BE model—even had the same combustion chamber shape, the same valve angles and sizes, and also had chain-driven camshafts.

GM Studied Japanese and German Engines to Try to Compete

The Quad 4 was a huge deal for GM, representing the company’s first real high-performance inline-four, Oldsmobile’s first entirely new engine design since the 1948 Rocket V8, and General Motors’ first all-new engine in, according to General Motors’ own admission at the time “several years.”

In the previously-mentioned December 1985 presentation to journalists by Oldsmobile Chief Engineer Theodore Louckes, he outlined the main factors that brought the engine to market. Among them was “competitive pressures from many smaller foreign products.” Louckes also talked CAFE standards and GM’s memory of the oil embargo of the early 1970s.

The goal was to build a world-beating engine, and to do that, GM assembled a “Skunk Works” team in 1982, which—after fielding a number of engine architecture proposals—chose a 2.3-liter inline-four, dual overhead cam engine with four valves per cylinder.

The choice of a DOHC four wasn’t surprising, since that’s what was all the rage, but Louckes mentioned that the choice of that specific size had much to do with the packaging constraints of a number of GM vehicles, saying:

The 2.3-liter four-cylinder engine is the largest displacement in-line engine packageable in our transverse configurations. While higher displacements can be achieved with “V” or opposed cylinder arrangements, we found that their higher complexity and cost would not be justified over the power and efficiency of this four-valve, four-cylinder configuration.

Key to the development was Computer Aided Design, which was still an emerging concept back in the early 1980s, and which GM used to size camshaft, rod, and main bearings, as well as to optimized the intake and exhaust systems of the Quad 4.

Also important was competitive benchmarking, with Louckes saying GM’s Advanced Product Engineering Department “provided the teardown and analysis of many of today’s modern engines from all over the world,” and that the Quad 4 incorporates a number of design technologies found within them.

Among the companies whose engines were studied were Mercedes, Porsche, Honda, and Toyota. In his presentation, Louckes compares GM’s new multivalve four to a 2.0-liter from Nissan, a 2.0-liter four-valve from the Toyota Camry, a 2.5-liter from Porsche, a 1.8-liter from Honda, and a 2.3-liter four-valve from Mercedes. Plus, in its press material, GM compares the Quad 4 to 16 valve engines from the Porsche 944S2, VW Jetta GLI, Acura Integra, Honda Prelude Si, Toyota Celica GTS, and also to Saab:

The Oldsmobile chief engineer concluded his presentation to journalists by saying that a 180 horsepower version of the engine would come soon, and that a 250 horsepower turbo Quad 4 (like the one shown below, which powered the aforementioned Indy 500 Pace car piloted by Chuck Yeager) was also on the horizon, though only the former—which had larger intake and exhaust valves than the regular Quad 4, as well as a 10:1 compression ratio, different intake and exhaust manifolds, altered valve timing, and an engine oil cooler—ended up coming out in 1989.

No turbo Quad 4 was ever offered even after being mentioned in numerous GM press releases, and even after all that effort to build boosted Quad 4 hype with the Aerotech.

Too” Thrashy” and Too Late

Even though GM had originally started its “Skunk Works” team in 1982, the Quad 4 engine didn’t hit dealers until 1987, and by that time—even with its distributor-less ignition system—it didn’t exactly feel new, according to contemporary reports like this November, 1987 issue of Changing Times Magazine (now called Kiplinger’s Personal Finance.)

“Well, the Quad 4 is here, and early reports are that the buffs are disappointed,” the author writes, going on to say that the engine was good, but not exactly fresh. From the story:

Lots of companies—among them Mercedes-Benz, Saab, Toyota, Acura, Nissan and Honda—already manufacture similar motors, and GM is following in their footsteps.

As for what the writer thought after driving an Oldsmobile Calais GT: “It was powerful and responsive, but the engine was also noisy,” the article reads, attributing the racket to chain-driven overhead cams instead of belts, and also to the engine’s relatively large size.

These noise and lack-of-novelty complaints were echoed across a number of car magazines in the late 1980s, with the former complaint coming to define the Quad 4 as GM’s “thrashy” little inline-four.

In their book Comeback: The Fall & Rise of the American Automobile Industry, which focuses specifically on the U.S. auto industry’s struggles in 1980s after Japanese automakers started building factories in the U.S., Joseph B. White and Paul Ingrassia describe how the Quad 4 didn’t exactly launch gracefully:

...GM was hard-pressed to show anything it had in production that broke new ground. GM trotted out its new four cylinder engine, called the Quad 4, which had four valves per cylinder instead of two per cylinder standard in other GM engines. The extra pair of valves helped the Quad 4 burn fuel more efficiently, and crank out more horsepower from a smaller block than the old Iron Duke that powered most of GM’s small cars.

[...]

But modern four-valve-per-cylinder engines were news only to people who’d never purchased a Toyota or a Honda. And as GM customers would discover, the Quad 4 was a rough, noisy beast compared to its Japanese competition.

In a May, 1988 issue of Popular Science magazine, author Dan McCosh compared three vehicles participating in the “latest trend in high-output engines”: four valves per cylinder. Those cars were the VW Jetta GLI 16V, the Chevrolet Nova Twin Cam 16 Valve, and Quad 4-equipped Olds Cutlass Calais. And though he liked the engine’s power, he considered the Quad 4 the least refined of the bunch.

Apparently it was awful, with the review mentioning that “the buzzing feedback of the Calais’s engine was bad enough to blur the numbers on my wristwatch when I gripped the wheel hard,” and attributing the issue to a “four-cylinder shaking force undamped by any countershaft-balancing arrangement.” McCosh concluded his take on the Cutlass Calais:

The Olds Cutlass Calais is impressive for both power and plushness, but the problems with driveability and noise at high rpm, where the Quad 4 produces its power, sometime had me wishing for a smoother V6 engine and an automatic.

To be fair, McCosh was a bit kinder on the “late to the party” message others had been writing about the Quad 4, saying it was thousands cheaper than counterparts from Porsche, Daimler or Saab, and that it wasn’t entirely derivative:

At first glance, the Quad 4 is a tardy entry in the multi-valve arena, following both European and Japanese four-valve cylinder heads to market...But a closer look shows significant breakthroughs in materials and manifold configuration, as well as an unusual ignition that supports Oldsmobile’s claim that the Quad 4 is the most efficient—and one of the most powerful—four cylinder engines on the market today.

So it seems that GM’s first entirely company-built entry into the dual overhead cam, four-valve per cylinder space wasn’t exactly knocked out of the park.

GM Made Significant Changes to Fix the Engine’s Faults

The Quad 4 didn’t have balance shafts, which are shafts built into the engine specifically to offset secondary forces that can yield engine imbalance and thus vibration. It wasn’t the only engine lacking this technology, but it was also fairly large, and this, some thought, was the source of the Quad 4's refinement problems.

Louckes, the Oldsmobile Chief engineer, admitted during his press briefing that one of the factors that held back public acceptance of four-cylinders was “second order shaking force,” but he said the Quad 4 performed well in that area and was “nearer to a modern 2.0-liter design than it is to other engines of comparable displacement.” Louckes also talked about “horsepower specific shaking force,” which he said was an indicator how the engine feels in the vehicle. “The Quad 4 is lower than the very efficiently designed Honda 1.8-liter, he said.” In fact, he called the Quad 4's smoothness “outstanding.”

As for balance shafts, Popular Science talked with him and learned that forgoing them was done to “avoid the small horsepower loss.” GM’s strategy to reduce imbalance, per Popular Science, was to use lightweight pistons, wrist pins, and connecting rods. In addition, it and other automakers like VW used “relatively long connecting rods to reduce angular changes during a piston stroke.”

Some suspect, though, that cost was a significant factor in the choice to forgo balance shafts.

Still, it’s clear that GM knew the engine was far from perfect when it came to refinement. That’s probably why, when Oldsmobile introduced the High Output Quad 4 in September of 1988, it put much focus on refinement, saying all Quad 4s have received or will receive “a number of minor refinements aimed at improving customer satisfaction.” Those mentioned include a new gear tooth profile for the oil pump for “quieter cold-start operation,” new engine mounts to transmission of “engine-generated noise and vibration into the body structure,” a cam chain sproket redesign to reduce whine, and more ribs on the transaxle of manual models to “further reduce final-drive whine.”

That’s a lot of noise-reduction stuff to mention in a press release, so it’s clear GM knew the engine had issues. The good news is that, in 1996, the Quad 4 got a major redesign and became the 2.4-liter “Twin Cam,” and one of the biggest selling points was reduced noise.

“More Torque, Less Noise In Gm Twin Cam Quad 4 Engine,” reads the August, 1995 headline by Automotive News, which says the new engine, while derived from the Quad 4" has a new block, crankshaft, head, intake manifold, and valvetrain, and that noise went down thanks to more direct-mounted accessories.

Richard Truett of the Orlando Sentinel also mentions in his 1995 article “a pair of counter-rotating balance shafts inside the engine that cancel out vibrations,” though according to a 1995 Popular Mechanics story, those had already been phased into the Quad 4 in 1995 prior to the Twin-Cam redesign (they were in the oil pan, and chain driven). Also, in 1992, Hemmings writes in a more recent story,“vibration-damping engine mount” had been phased in as well.

The Hemmings story also mentions mentions other running changes to help address some alleged reliability problems involving oiling and cylinder heads, writing:

There were a host of other problems as well: cracked heads, blown head gaskets, timing chain noise, oiling issues and so on. A variety of running changes were made to the engine: Different crankshafts and different connecting rods were employed, revised oil pans were used and there were updates to the block, through the 1990s.

In any case, by the time the Quad 4 grew up and became the Twin-Cam, it had become a much more refined, more reliable version of the Quad 4, and it soldiered on in Chevy Cavaliers, Oldsmobile Aleros, Pontiac Grand Ams and Pontiac Sunfires into the early 2000s. Some folks have even swapped the engines—both the regular Quad 4s and the Twin Cams—into their hot rods due to their good power, small size, and resemblance to an old Offenhauser design.

With the Quad 4, General Motors took one of its biggest steps into the modern four cylinder world, and undertook a clear attempt to push back against the imports. The company has come along way since then, even showing off a thoroughly advanced four-cylinder engine in a full-size Silverado pickup in 2018, though even that one received its share of criticism.