Introduced in 1982, General Motors’ rear-wheel drive G-Body platform was essentially a revamped version of the A-Body platform that had underpinned boxy late ‘70s and early ‘80s intermediates like the fourth-generation Oldsmobile 4-4-2 and fifth-gen Pontiac LeMans. Not to be confused with GM’s full-sized, front-wheel drive G-Body architecture that was in production from 1995 to 2011, the rear-drive G-Body is perhaps best known in the performance world for the turbocharged and much-beloved Buick Grand National, while other hopped-up G-Bodies like the fourth-generation Chevrolet Monte Carlo SS and fifth-gen El Camino SS came from the factory packing a 5.0-liter naturally aspirated V8.

These models gave the platform some street cred in the hot-rodding scene, but the G-Body was primarily used to produce the sedate, high-volume people movers of the day. While those mainstream vehicles weren’t setting anyone’s hair on fire with their capability, a beneficial side effect of their popularity is that they now offer gearheads a relatively affordable, easy-to-find canvas for performance builds that includes the core mechanical features of classic muscle cars – mid-sized dimensions, a rear-drive layout, and Chevy small-block compatibility right out of the box – all without the costliness that inherently comes with architectures that are directly associated with performance.

Shop LS Swap Kits for GM G-Body platforms here.

“Over the past 10 years or so, we’ve seen what we like to call the ‘Mustang tax’ take shape, and it’s not just applicable to Fox-bodies,” says Holley Performance product manager and resident G-Body guru, Jake Anderson.

“It also applies to Camaros, and pretty much anything else that was marketed as a performance vehicle at the time. The prices of older cars that fall into this category keep going up and up. But G-bodies are really good starter platform that came from the factory with a V8, they have a massive transmission tunnel, and the engine bays are really large, which makes adding accessories really easy. They also have a triangulated four-link rear suspension that’s very similar to a Fox Body Mustang, and there were a variety of different body styles: two-door coupes, sedans, wagons, and pickups. That means you can go in a number of different directions with the build, whether you want autocross-style handling, an all-out drag car, or simply a fun cruiser. And because most G-Bodies weren’t originally marketed as performance cars, they’ve kind of flown under the radar as far as the Mustang tax goes.

That said, these cars are roughly 40 years old now, so you have to keep in mind that some stuff is going to be worn out just from age. And since most of them weren’t set up for performance to begin with, there’s a lot of room for improvement.”

With that in mind, we’re taking a look at a collection of the upgrades and modifications that will help you get the most out of your G-Body project.

Building A Solid Foundation

Anderson points out that most G-Bodies weighed in around 3,000 pounds – give or take a hundred pounds or so depending on body style and trim – which makes them roughly half a ton lighter than most of today’s high-performance coupes. And that lightness means that relatively small upgrades can have a substantial impact on the vehicle’s performance. But he notes that it’s important to make sure that the car is ready to handle additional power before you bring it into the mix.

“The first thing I would encourage someone to do when starting a G-Body project with a stock or near-stock example is to look at the motor mounts and the steering shaft. The original rubber motor mounts are likely to be brittle and cracked from age, and good polyurethane motor mounts can really make a difference here. Most of these cars were tuned to be soft and floaty from the factory, which causes the engine to twist and flex, and that robs horsepower from the rear wheels. Any time you can replace a rubber component with a poly component, it’s going to stiffen things up a bit and make everything feel a little more responsive. So upgrades like the Hooker Blackheart clamshell mounts and poly insert will liven things up in that regard and lay the groundwork for future mods.

The other thing I’d recommend addressing right off the bat is the steering shaft. The factory G-Body steering shaft has a rubber rag joint in it, and that creates a lot of slop in the steering. The factory shaft is also just really large, and that can create potential clearance issues with aftermarket headers and things like that. The Blackheart steering shaft eliminates that rag joint entirely, which will give you better-than-factory steering response with a direct bolt-in part. And it’s much more compact than the factory component, so you’ll have more room to work within the engine bay.”

For those seeking a simple upgrade that will improve performance and enhance the driving experience without breaking the bank, Anderson suggests ditching the restrictive factory exhaust for an aftermarket system.

“Sound is a big part of vehicle’s personality, and this can make the car sound like a million bucks even if you don’t have a million bucks invested into it. A good stainless cat-back system like the one offered by Hooker will completely transform the soundtrack. It will also be a lot less restrictive, which will translate to more horsepower and torque, and it’ll support a lot more power than the stock exhaust can.”

Moving back into the engine bay, he recommends looking at the intake manifold and carburetor setup to find other substantial performance improvements.

“The factory two-barrel carb and intake setup is a major bottleneck, so I generally steer folks toward the Weiand Speed Warrior four-barrel intake for starters. Not only does this intake flow leaps and bounds better than the stock part, it also opens up a range of options for four-barrel carburetors that you can pair it with. With a mildly modified small-block, our engineering team recommends a 600 CFM Holley Street Warrior 4160. These upgrades are going to allow the engine breathe better, and they’ll support more power as you add things down the road.”

You’ll also want to make sure that the fuel system can handle the engine upgrades you’ve made.

“You can introduce all the air you want, but if you don’t have the fuel to support it, you won’t realize the full benefit of those upgrades,” says Anderson. “And because of the age of the platform, these cars are old enough that they’re starting to have issues with rust, build-up in the lines, and things like that. So I’d start with a stock replacement tank and pair that with a high-volume fuel pump. A pump like Holley’s 350 LPH fuel pump module will support upwards of 500 horsepower in this application, so you’ll have plenty of headroom to work with.”

That headroom will come in handy with Anderson’s next recommendation.

“A 4150-style plate nitrous kit will work great on a combination like this. It’s a simple install and you can safely run a 100-horse shot on a mostly-stock small-block Chevy from that era, and the kit is capable of flowing a lot more if you choose to beef up the engine internals. And it’s worth keeping in mind that even a 100-horse shot in a car that originally made 150 hp is really going to wake it up.”

And when you’re increasing the power of the vehicle by more than fifty percent, it’s important to make sure that the rest of the car can keep up.

“At this point I’d also be looking at brake upgrades for safety’s sake – the factory brakes just weren’t designed to contend with such big increases in power,” he says. “Upgrade kits like the Baer Classic Series for the front and rear of the car will drastically improve pedal feel and overall stopping power as compared to the factory stuff. It might not be as exciting of an upgrade as a power adder or something like that, but all the horsepower in the world isn’t worth much if you can’t stop the car.”

The Alternate Route To Big Power Gains

While there are plenty of ways to get lively performance from a factory Chevy small-block from this era, engine swaps have become hugely popular in G-Body circles as well. And it should come as no surprise that the venerable LS family of small-block V8s are the most widely used mills for these transplants.

“If the factory engine is worn out, or you’re simply looking for more power than that original small-block Chevy can withstand, even swapping in a junkyard LS with 150,000 miles is going to double or triple the power potential,” says Anderson. “The LS dominates this market right now because they’re cheap and there are still a ton of them out there. The smaller 4.8-liter and 5.3-liter LS V8s are popular for these builds because they have thick cylinder walls that can handle a lot of boost from a power adder like a turbo or a supercharger, and they’re both easy to find and inexpensive because they were mainly used in trucks and SUVs. With a good power adder and the right modifications applied to a fourth-generation 5.3-liter LS, you can safely push the horsepower levels into four-digit territory, and it will live for a long time. In terms of bang for your buck, it’s tough to beat.”

Anderson says that would-be swap projects will require three main components in order to accommodate an LS in a G-Body engine bay.

“You’ll need engine mounts, a transmission crossmember, and an oil pan that will provide the necessary clearance for the K-member. And Holley Performance has made it easy to find all of these parts by putting them together in one LS swap kit.” This kit is compatible with G-Bodies that are equipped with either a TH400 or 200-4R automatic transmission. Those who want to use a Tremec T-56 or T-56 Magnum six-speed manual gearbox instead can do so with this version of the kit. Accessory drive kits can also come in handy if you’ve brought a power adder into the mix or have an upgraded cooling system that takes up more real estate than the factory components.

From here, it’s really about deciding where you want to go with the build. For folks that want to keep things simple and low profile, Anderson recommends Hooker Blackheart LS swap exhaust manifolds for improved flow characteristics with minimal packaging compromises, and he says that the Holley Lo-Ram is a great option for those seeking a performance-tuned intake manifold that will still fit under the factory hood.

Shop LS Swap Kits for GM G-Body platforms here.

“With these types of swaps, more often than not you’re going to be working with an LS that came from a truck or an SUV, so parts like the intake manifold are optimized for the low RPM range that a truck typically lives in. But for a performance application, you can shift that powerband up a bit and get more power out of it by switching to an intake manifold design that’s designed specifically for performance. Lo-Rams also have a lot of options as far as fueling goes. They’ll accept two different heights of injectors, and there’s also a 16-injector option for folks who want to run methanol or do a dual-fuel setup for a drag and drive event, or something along those lines.”

He adds that although it can be tempting to chase a number when doing swaps like these, it’s important to keep your eye on the big picture.

“It’s easy to get tunnel vision. Bolting on horsepower is definitely the most fun aspect of a project like this, but you can’t neglect the other systems of the car, otherwise you’ll get into a situation where the car is so imbalanced that it’s unsafe. The more power you add, the more you need pay attention to the things that aren’t as instantly gratifying – like slowing down and cornering. You can bolt in a lot of power pretty easily, but if you want it to be truly usable, you have to make sure that you’re addressing all of the different aspects of the vehicle’s performance.”

Check out our other platform-focused modification articles.

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Tech Tips: Holley Essential Mods | Chevy OBS GM Pickup/SUV

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