LS Intake Manifolds - Engine Builder Magazine

LS Intake Manifolds

LS swaps are popular for many reasons, but there are a lot of variations and details to sort through – more of them than you may expect – and many of them are associated with the intake manifold.

When it comes to trying out new methods and theories to improve upon performance, often times, we’re learning using the old-fashioned way through trial and error. After any type of modification, the butt dyno is only good to a certain point. You could usually feel a difference any time you made a change in tuning, such as a different accelerator pump cam or distributor advance weights, but you really didn’t know for sure – without a dyno or track time – what type of difference you made.

Quick bolt-on “power adders” were usually the same way and sometimes you felt no difference, but one particular bolt-on that left no doubt about loss or gain was the intake manifold. This fact made it one of the more interesting components, especially to understand why it had such an impact. It didn’t take long to learn that wide open plenums and short runners would move the torque curve up the rpm range, and that long runners would move the torque curve down the rpm range.

It was easy to “visualize” the difference in air velocity and volume and understand the difference it made, but the importance of it in relation to engine efficiency is often understated, and the path of technology led to the internal airflow characteristics of an intake being where the majority of modern research efforts have been focused. When the intake valve opens, a low-pressure area develops in the intake runner. Air then flows through the runner into the cylinder in order to equalize the pressure.

When the intake valve closes, the velocity of the air creates high pressure that bounces back up the runner. The resulting resonance from this effect, as it turns out, is the driving factor in manifold performance. While there will always be the same fundamental shift in torque curve based on runner length and volume, managing the effects of this pressure inside a manifold are a constant area of research and LS intakes are no exception.

LS swaps are popular for many reasons, but there are a lot of variations and details to sort through – more of them than you may expect – and many of them are associated with the intake manifold. From the factory, there is a clear difference between the LS car and truck manifolds. The truck manifolds are taller (by over 3 inches) and don’t flow the same at high rpm, so car manifolds are more desirable for high-horsepower applications.

Most of the Gen III intake manifolds had cable-operated throttle bodies, and the Gen IV intakes had throttle-by-wire. Most of the manifolds will only work with the type of throttle body they originally came with, but there are some that will work with either type. There’s about a 50/50 split on the engines that came with cathedral port or rectangle port heads, but there’s more to it than matching the ports. Even if a manifold bolts on, in some cases the bolt patterns of the fuel rails, MAP sensor and throttle bodies were different, so you had to think ahead.

Of the more common Gen III cathedral port models, the LS6 manifold puts up better numbers than the LS1 to the tune of about 20 hp and 15 ft.-lbs. of torque. As a refresher, the LS1 was our first introduction to the Gen III small blocks in the ‘97-‘04 Corvette, the ‘98-‘02 Camaro/Firebird and the ‘04 Pontiac GTO, with an aluminum block and 305-350 hp, depending on application. The LS6 was the 385-405 hp monster that powered the ‘01-‘04 Corvette Z06 and ‘04-‘05 Cadillac CTS-V.

Surprisingly, the standard truck intake from this generation of LS engines performs quite well, nearly matching the numbers of the LS6 manifold, but most people think the truck intakes are just plain ugly. Where there’s a will there’s a way and many people have found ways of smoothing them out and making them look downright slick!

Most of the Gen IV engines featured rectangle port heads, and the LS3 intake is widely known as one of the best factory LS manifolds. The LS3 was the aluminum block 426-436 hp 6.2L version, produced from 2008-2017 for the Corvette, Pontiac G8, Camaro and Holden models. As with the cathedral port models, the rectangle port truck intakes come close to hitting the performance of the LS3, only with the same objection of looks, and like all the truck intakes, they are taller and may not fit under the hood of some cars.

The aftermarket industry has embraced the Gen III and Gen IV small blocks, as much as and maybe more than their predecessors, and while there are many possibilities with factory components, aftermarket intakes and accessories have really opened up the options and proven that there’s power to be found. 

“Basically, for the LS platform, it’s a la carte,” says Bryan McTaggart of Holley. “It’s what do you want and how do you want it? We have everything from a High Ram EFI manifold to Low Ram intakes that have good flow but hide under the hood. We have cast manifolds, fabricated sheet metal manifolds and composite manifolds too.”

Among the options that can make an LS swap easier are throttle body adapters for various intakes to go from three to four bolts, as well as clocking adapters when battling accessory clearance issues. Fuel injector and fuel rail adapters and fittings add to the scope of adaptability as well as throttle cables, brackets and electronic throttle pigtail adapters.

But let’s get serious. What about the power and what’s the most popular? As with any engine build, there are too many variables to state that one intake outperforms another and it all comes down the individual builds, as well as ultimately what you’re building the car for. No matter how you stack it, you’re still going to sacrifice low-end for top-end gains and vice-versa, but there are many popular aftermarket intakes that would sit proudly atop any LS build.

A comparison of the stock LS3 intake against a few of the popular aftermarket manifolds yielded the following results:

Are carburetors your game? Here are some test results comparing a stock LS3, then swapping out to old school.

To have some fun, Holley tested their Hi Ram intake setup on a 440 cid LS7 with different uppers for comparison. Specs for the engine were an eight-counterweight crank, 13:1 compression, LS7-style CNC’d heads, LSC dry sump setup, ATI damper, hydraulic roller camshaft, Holley 85 lb./hr. injectors, and Hooker 2” primary headers.

Above is a LowPro V.2 intake manifold from Frankenstein Engine Dynamics. These LowPro intakes are available for LS1, LS3, LS7 and LT1and LT4 with and without port injection. The LS3 and LS7 are available for dual injectors as well.

Starting with dual quad 4500 throttle bodies, this combination cranked out 754 hp and 624.9 ft.-lbs. of torque, but pointed out that this is primarily a drag racing or big-cube setup, with low-end sacrifices. Next were dual 4150 throttle bodies, which put up the numbers 747.7 hp and 621.3 ft.-lbs. The 4150 throttle bodies only provided half the cfm of the 4500s, but still had close numbers, and are much better suited for a street application.

Then came a much simpler and more affordable combination with the Hi Ram and a single 105mm throttle body upper, cranking out 732.6 hp and 606.5 ft.-lbs. Wrapping it up was the MSD Atomic Air Force single 105mm throttle body, which came in at 718.7 hp and 621.5 ft.-lbs. The numbers are lower, but this manifold had the lowest profile and would fit under most hoods, as well as provide the best low- to mid-rpm performance. 

These various comparisons are the perfect example of the horsepower you can gain, as well as the sacrifices and the simple truths that we already know. The right manifold for any LS depends on the final application. EB

You May Also Like

The Road to AAPEX Season 2, Ep 7

Rolling through Nebraska, Babcox Media’s Joe Keene meets kindred spirits as he drives the rare Lincoln Blackwood he refurbished for his journey to AAPEX. Along the way, he meets a family traveling the Lincoln Highway section by section, taking in sights such as the Great Platte River Road Archway Monument and the Classic Car Collection,

Rolling through Nebraska, Babcox Media’s Joe Keene meets kindred spirits as he drives the rare Lincoln Blackwood he refurbished for his journey to AAPEX. Along the way, he meets a family traveling the Lincoln Highway section by section, taking in sights such as the Great Platte River Road Archway Monument and the Classic Car Collection, both in Kearney, Neb., and the Golden Spike Tower in North Platte, Neb.

Valve Springs

High-frequency fatigue, also known as harmonics, are a ubiquitous challenge in racing engines and can potentially wreak havoc on the valvetrain if left unchecked. Well-designed valve springs play a pivotal role in managing this, ensuring essential stability, and minimizing wear on valvetrain components.

The Latest on Lifters

For racing, a common trend to eliminate the problems associated with hydraulic lifters are the use of limited or short-travel hydraulic lifters. A reduction in plunger travel, which is usually about half that of a traditional full-travel lifter, reduces the amount of oil required to fill the lifter, which in turn reduces the compression of aerated oil.

Heavy-Duty Diesel Engines, Equipment and Replacement Parts

Relying on OE manufacturers like Caterpillar, Cummins, Detroit Diesel and Waukesha has always been an option, but diesel equipment owners are now more than ever seeking the aftermarket as a more viable solution for replacement parts.

Diesel Piston Technology

Diesel and heavy duty go hand-in-hand. There’s no way around it. High compression causes high cylinder temperatures, with peak cylinder pressure often as high as 2,700 psi (or higher). This high pressure and high heat only have one thing in mind, to beat relentlessly on the first thing to get in the way – the pistons.

Other Posts

The Coolest Engine Shop Ever? Inside Noonan Race Engineering

Even before Noonan Race Engineering completed its new Engine Technology Facility, this was an engine shop we’ve been wanting to see inside for quite a while. If you’re at all familiar with Noonan Race Engineering, its engines and its components, then you already know it’s the the kind of stuff billet aluminum racing dreams are

Speedmaster LS3 Dual Plane 4150 Midrise Air Intake Manifold

Speedmaster®, a leading global automotive performance brand specializing in high performance engine parts, is pleased to introduce a new Chevy/GM LS3 Dual Plane 4150 Midrise Air Intake Manifold.  Related Articles – Motor State Distributing Adds Monit Motorsports to its Offerings – Calico Coatings Launches Joint Venture with HEF Group – NASCAR’s 2024 Drive for Diversity

Speedmaster Chevy BBC 454 Downdraft 8 Stack EFI Intake Manifold System

Speedmaster®, a leading manufacturer of high-performance engine components, is set to debut its new Chevy BBC 454 Downdraft 8 Stack EFI Intake Manifold System with a higher state of tune and engine versatility at the 2023 SEMA Show. With tight air/fuel ratio control, this precision cast aluminum 50mm IDA style throttle body ensures optimal idle

Speedmaster Introduces Chevy Gen V LT1 Downdraft EFI Intake Manifold System

Related Articles – Walker Products’ High Performance Catalog – Silver Seal Deluxe Valve Stem Height Gauge Set – Harrop TVS2650 Supercharger Kit for Ford’s 7.3L Godzilla Speedmaster® is set to unveil one of the company’s latest groundbreaking engine products at the 2023 SEMA Show – the Chevy Gen V LT1 Downdraft 8 Stack EFI Intake