Spotter’s Guide to Identifying Factory LS Intake Manifolds

With some 40 GM part numbers covering the list of intake manifolds for more than 25 variations of the Gen III and Gen IV LS engine family, identifying a swap meet intake or planning a manifold swap can get a little confusing. This handy spotter’s guide to LS intake manifolds should help.

Known as the third and fourth generations of the GM small-block family, the LS engine architecture was introduced in 1997 with significant changes over the Gen II LT1 and LT4 engine line used in GM cars from 1992 up to 1997.

Millions of LS engines were produced and are now favorites for swaps into early model cars and trucks.

In fact, there’s very little in common between Gen II and Gen III/IV LS engines other than a few dimensions like the 4.40-inch bore spacing and a 2.10-inch rod journal. Everything else changed, including the cylinder block deck height, the firing order, and the connecting rod length.

LS engines were produced for cars and trucks from 1997 through the 2013 model year. That’s when the LS family was replaced by the current Gen V LT engine group, again, designed for use across the car, SUVs and pickup segments. There’s even a V6 version of the LT small-block. With millions of LS engines installed in production GM vehicles over 16 years, there are plenty available for swaps into older cars and trucks. Sometimes a salvage yard engine will be missing an intake, or perhaps the goal is to build a LS engine from scratch. Again, this guide will help identify intakes at swap meets, junkyards or even checking out listings online.

Required Disclaimer

A note of caution: this list was compiled from a variety of sources and is not guaranteed to be all-inclusive. In fact, just as this story was completed, two more numbers (89017365 and 89017363) were discovered on an internet forum. We checked them out with a reliable parts source and the comment that came back said, “This shows ZERO OEM applications in the GM catalog, however it is a good part number.” There may be an occasional discrepancy due to new or discontinued parts numbers, but this list as close to complete and accurate as any other directory available online. We’ll certainly update it as readers identify mistakes and help verify the correction.

Among the numerous innovations introduced with the LS engine line was the use of composite intake manifolds for both the car and truck versions of the V8. The first manifold for the LS1 Corvette engine was constructed from about eight pounds of injected nylon. It was lightweight and flowed well, given the dimensional restrictions placed on the engineers when the C5 Corvette was designed. Cut open one of these intakes and you’ll find three pillars supporting the flow tubes over the base. According to author Will Handzel’s excellent book, How to Build High-performance Chevy LS1/LS6 V8s, those stands were needed to control resonance produced from the flat floor, so there obviously was a learning curve with this new material.

The shape of the intake’s floor distinguishes the LS1 (left) and LS7 intakes. The LS7 has a flat floor while the LS1 has a cavity running the full length. Also note the difference in ribbing between the ports. The LS1 has large “X” ribs while there are square ribs on the LS7.

The LS1 was the first of the LS engine line, so improvements followed over the years, including the release of the LS6. That intake flowed more volume and eliminated the EGR valve. Naturally, owners of LS1-powered cars looking for upgrades turned to the LS6 intake as a viable option. And it’s a relatively easy swap.

Unfortunately, the LS6-to-LS1 conversion is about the only easy or practical LS-intake swap we could identify. In other words, not all intakes will swap with each other. There are a number of hurdles to clear when looking over the list, simply due to the wide range of engines developed from the LS architecture.

Though these are aftermarket manifolds, they demonstrate the difference between rectangular port (left) and cathedral port designs.

Though these are aftermarket manifolds, they demonstrate the difference between rectangular port (left) and cathedral port designs.

Distinguishing Gen III And IV intakes

Foremost is the difference between Gen III and Gen IV. The earlier engines had cathedral-port cylinder heads while the latter generation sported rectangular-port heads. The LS7 is the lone wolf in the entire lineup, with a wider bolt pattern and larger intake ports, so there’s no interchangeability. Also, this guide does not cover the supercharged LSA and LS9 intakes, since they’re an integrated part of the supercharger assembly.

Most Gen III engines, except for the Corvette and select trucks, had manually operated, cable-controlled throttle bodies, while the Gen IV engines had throttle-by-wire, which simplified functions like traction control and cruise control. This complicates potential cross-breeding between different intakes and throttle bodies, though some intakes like the LS6 will work with both manual and electronic units. And even within the same generation of engines, there were differences between some models. For example, the LS2 intake physically fits on a LS6 engine, but the fuel rails, injectors, MAP sensor and throttle body bolt pattern are all different. And these differences grow even more when comparing the car and truck versions, which is a shame because there are so many more used truck engines available for a bargain.

Examples of the LS3 and LS6 intakes from different generations of the LS engine family. These composite intakes are manufactured from a nylon with glass-fiber reinforcement.

Making sure the hood clears

That’s not to say you can take popular truck engine like the 6.0-liter LQ4 and drop it into a G-body or Gen-three Camaro. The problem will be hood clearance. Truck engines always had a taller intake, allowing longer runners for better low- and mid-range torque. The car engines had shorter runners for better top-end performance, but also, for improved hood clearance. In fact, there was generous hood clearance on many cars due to efforts to improve pedestrian protection. The theory was that if a pedestrian was struck and landed face down on the hood, there would be some flexing of the body panel to absorb impact energy. Without that clearance, the intake manifold would act like an anvil and flatten the poor guy’s face and skull.

Of course, the aftermarket wasn’t obligated to meet these clearance issues, so companies could design intakes with longer, larger (and therefore taller) runners to improve airflow and power. Also to note for performance enthusiasts, the factory GM intakes are not designed to be modified. While injected nylon is durable and can even handle some boost, the runner walls are not thick enough for accept any grinding or porting. Aftermarket intakes, especially cast-aluminum models, will be easier to open up, if desired.

A Manifold Only A Mother Could Love

The other downside to using truck manifolds in a car is that the fact that they are butt-ugly. Performance enthusiasts want to show off their engines, and the intake is the centerpiece of the powerplant. But GM did not design any cool factors into its truck intakes, especially when compared to the curvy, flowing car models. The trucks are just plain hideous with the support ribs and accessory bosses. That’s why they came with boring engine covers on the production line. However, the truck intakes do have their followings.

A Pretty Truck Intake

Mark Burch, who goes by the moniker AGearhead4Life on Facebook and YouTube, is well-versed in swapping LS engines into earlier model cars and trucks. He’s also had plenty of experience working with different intakes. He agrees that the truck intake looks horrible, especially if found under the hood of a car. So he developed a method of smoothing over the truck intake with just a soldering iron and a lot of patience. Check out this earlier story on Burch’s project, which includes a video.

“I prefer the truck manifolds,” says Mark Burch, an innovative DIYer with a popular YouTube channel who has swapped numerous LS truck engines into other applications. “It flows better than the LS1 and almost as good as the LS6.”

Burch has also swapped car intakes onto truck-based long-blocks and can attest to the numerous issues that must be addressed. For example, early trucks from around ’99 to ’04 usually have fuel return lines while the LS1/LS6 car intake has just the feed line.

“Some people get confused when you don’t have the return line,” says Burch. “Most of the cars that we’re swapping LS engines into have two lines, so it’s simpler with the truck intake having the fuel-pressure regulator built into the intake.”

If a shorter intake is necessary for hood clearance, then there will likely be interference issues with bolting a car intake to a truck engine. The truck intakes are a little taller to clear the accessory drive and water outlet neck from the water pump. Options include installing the car water pump and moving the idler pulley. Also, some people will dent the side of the neck and cut the cruise-control tab off the throttle body to make the truck water pump work with a car intake.

“Switching to the car water pump requires spacers so the pulleys align,” warns Burch, adding that others with fabricating skills will plug the existing outlet neck and make another one that clears the drive.

Solving Problems On The Swap

Experienced engine swappers always run into some type of problem when introducing an alien engine to a different car. Issues that could surface include interference with the crossmember, clearing coolant and hydraulic lines, routing the exhaust and wiring the engine if EFI is retained.

Here are a couple of Mark Burch installations. Note the difference in the neck outlet on the water pump. The vertical neck is off a truck pump, and the horizontal outlet is from a car pump.

“Remember, the car and truck intakes have different injectors and fuel rails,” says Burch. “The truck injectors are shorter, so if you put car injectors on a truck intake, you need spacers on the fuel rail mounting points. And the wiring connections are also different.”

The LS4 is the only front-wheel-drive LS engine, so its intake won’t help with any traditional north-south swaps.

Other issues that need to be addressed include sensor locations, especially the MAP sensor, fuel-line plumbing and throttle bodies. The car and truck throttle bodies aren’t always the same size. For example, one source says the LS1 Corvette had a 75mm throttle body while the LQ4 and LQ9 truck engines came with 80mm throttle bodies. Other sources tell us the both car and truck cable-operated throttle bodies measured 78mm. Another concern is routing of the air inlet. It was straight on the cars and curved to the fender on the trucks. Again, the aftermarket will likely offer a convenient inlet and air-cleaner solution.

If you do find a nice 6.2-liter L92 truck engine and want to drop it into a ‘60s or ‘70s car, the easiest solutions would be find an aftermarket accessory drive designed for the LS3, then you could pick and choose an intake from Chevy Performance or the aftermarket to clean up the engine and add horsepower. As far as engine management, there are plenty of aftermarket ECUs that make LS engine swaps a breeze in that department.

Truck engines like this 5.3-liter L33 came with covers to hide the efficient, but ugly intake. Note the water neck and how it would interfere with the throttle body on a lower-profile intake.

As you can tell by now, this LS intake spotter’s guide can hardly be used as a swapper’s guide. There are simply too many potential issues to map out a plan for interchanging manifolds within each generation. Whether it’s throttle-body mounting and actuation, sensor location or fuel system hookup, there are too many details to research and validate. Rather, these charts will help you with finding replacement intakes, used-parts inventory and swap-meeting shopping. If you’re walking aisles at a swap meet or checking out used parts online or at a salvage yard, be sure to follow general common sense guidelines, such as checking for leaks or any other damage. The intake should come with a throttle body, injectors, sensors and fuel rails – or you may have a tough time finding compatible replacements.

Again, feel free to contact us if you spot any inconsistencies or mistakes in this spotter’s guide.

About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World.
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