Chevy LS3 Intake Manifold Upgrade Guide
It’s no secret that the Chevy LS3 is an engine built for peak performance. With its placement in the C6 Corvette and Camaro SS, the LS3 has all of the race-tested trimmings that you’d expect from a Chevrolet V8. For that reason, the LS3 is a remarkably well-optimized engine from the factory. One of the LS3’s greatest strengths is its factory flow numbers. That is the case for both the LS3’s rectangular-port heads and factory intake manifold.
Intakes aren’t a cut-and-dry performance part for the LS3. With some other engines, there’s a clear winner in the aftermarket intake manifold race, but the LS3 is a bit more nuanced. Since the factory design is so good, higher flow figures aren’t always the goal of an upgraded LS3 intake manifold. Some LS3 enthusiasts swap their factory manifold for a new one to move power around the rev range.
In this guide, we’ll discuss the benefits of upgrading your Chevy LS3 intake manifold. We’ll cover some of the most convincing reasons to do so and also recommend some intakes for different applications.
Upgraded LS3 Intake Manifold Considerations
There’s a lot to take into account when thinking about upgrading your LS3’s intake manifold. Quite a few of those considerations come from the other internal parts that work with the intake manifold. Intake runner length, plenum size and shape, camshaft pairing, and displacement all play a big role in how an intake manifold works with your build.
Intake Manifold Runner Length
One of the primary characteristics of an intake manifold is the length of the internal runners. Intake runner length needs to be carefully considered depending on how you want your car to deliver power. Runner length has a significant impact on where in the rev range power and torque peak. For that reason, some intake manifolds are better for different applications.
The world of intake manifold runners is one full of debate and a lot of math. With that being said, there are some overarching principles that make LS3 intake runner length a bit easier to digest. In general, short and wide intake runners move the torque curve up the rev range. The converse is true for long and narrow runners, which move the curve down the rev range. Bringing flow into the conversation, a manifold with shorter runners will consistently outflow a manifold with larger runners of the same diameter. Despite the additional flow, it isn’t always the case that manifolds with short runners produce more power. The primary difference is where the power peaks.
Most of the math associated with this effect has to do with low and high-pressure changes within the cylinders and intake runners themselves. When the intake valves are open, a low-pressure wave is created by the downward-moving piston. The low-pressure wave travels through the runners and draws air into the cylinder from the manifold. An LS3’s manifold runner length is related directly to the amount of time that this pressure wave takes to reach the manifold plenum. Longer runners are therefore better at lower engine speeds, where the waves have a longer period of time to reach the plenum before the intake valve closes. The opposite is true for short runners, where the wave has less time to travel, and therefore functions better at high-rpms.
Intake Manifold Plenum Size
Beyond intake runner length, which is still unquestionably the most significant design aspect of an LS3 manifold, plenum size is also important to consider. As we have already covered, the intake plenum is where air is held after entering the manifold through the throttle body. The volume of the plenum is crucial, as it needs to be able to hold enough air to supply the engine through the rev range.
An aftermarket LS3 intake manifold with an undersized intake plenum can lead to poor engine performance, especially at high-rpms. When the plenum is too small, the engine can draw in incoming air faster than the manifold can refill. This results in sluggish engine response or even a stall. A smaller plenum can increase low-rpm performance, but will let you down as the revs climb.
On the other hand, an intake plenum that is too big can also have adverse effects on performance. A large-volume plenum can significantly reduce the velocity of incoming air, which is also a problem. Air velocity is an important variable in terms of manifold design. The higher the velocity, the faster the intake ports and cylinders can fill with air. The result of poor air velocity is decreased engine response at low rpms.
The ideal intake plenum design is one that provides the maximum amount of volume without compromising air velocity too much. Aftermarket LS3 intake manifolds usually have a larger volume than the stock 3.7L plenum. With that being said, you don’t often see plenums over a 5.1L volume. As an important end note on plenums, shape matters too. The flow pattern and turbulence of air entering the plenum has a significant impact on velocity. Better air management often translates into better engine performance.
Intake Manifold Fitment
One of the most common upgraded intake-related problems that Vette owners, in particular, run into is clearance. Oftentimes, aftermarket Chevy Smallblock intake manifolds extend beyond the height limits of the factory hood. That’s usually because the manufacturer opted for a plenum design that is more vertical than it is wide. Since the C6 has a very slim frontal profile, there isn’t a lot of vertical space to work with.
There are generally two primary solutions to this issue: get a high-profile hood or cut a hole in the stock one. While it is hard to pin down exact figures in terms of C6 hood clearance, it is often concluded that a manifold with a vertical profile of over 6-inches will be too tall to fit under a stock hood. Obviously, if you are throwing an LS3 into a different chassis, that figure is different. Since manifold clearance is a common issue for the C6, there are numerous high-profile hoods available for it. High-profile C6 hoods come in all kinds of shapes and sizes, so it really boils down to appearance and personal preference. Otherwise, if you like the aggressive look of internal components peering out, a hole in the stock hood will do just fine.
Other Factors and Considerations
Choosing the right intake manifold goes beyond just the manifold’s performance itself. The key to choosing the right intake for your 6.2L LS is making sure that it works in unison with your other engine upgrades. For example, another very common LS3 modification is an upgraded cam, as the LS format responds very well to them.
Cam duration vs runner length is a debate that rages on in the LS community and there isn’t a set answer. There is a good argument for matching longer runners with a larger cam that provides better high-rpm performance. The balance between the increased low-end performance provided by longer runners and the high-end performance provided by longer-duration cams can yield good results. On the other side of the argument, the inverse can also be a good matchup from a tuning perspective. Matching short runners that provide high-rpm performance with a larger cam that favors a high-rpm curve can be a good combination if you are trying to tune for power in a specific part of the rev range. This is certainly a very simplified explanation of ram tuning and there is much more that goes into it that we don’t have the space to explain here.
Throttle body size also plays into LS intake manifold performance to a certain extent, especially as efficiency in the rest of the system increases. At a certain point, the factory 90mm LS3 throttle body can choke performance by not supplying the plenum with enough air. Installing a larger diameter throttle body is a very common LS3 mod. That is especially true when combined with an upgraded intake manifold. If you are interested in learning more about LS3 throttle body options, check out our LS3 Throttle Body Guide.
Upgraded LS3 Intake Manifold Suggestions
By this point, it should be clear that there isn’t a one-size-fits-all intake manifold that is best for the 6.2L Chevy V8. In fact, there are many different intakes with varying runner lengths, plenum sizes, and varying shapes that work well. It really boils down to where you want your LS to make peak power and torque figures. For that reason, we’ll suggest a few LS3 intake manifolds that serve different purposes.
- Sniper EFI Fabricated LS3 Intake Manifold
- Performance Design Carbon pTR Adjustable Manifold
- Edelbrock Pro-Flo XT Intake Manifold
Our Top Pick – Sniper EFI Fabricated LS3 Intake Manifold
RPM Power Band: 3,500 – 8,000rpm
Intake Runner Length: 5.512”
Price: $1,159.00
Purchase Here: holley.com
Holley is unquestionably a leading name in the world of LS performance parts. In business for over 100 years, it would be an understatement to say that they know what they are doing. Their Sniper EFI Fabricated intake manifold is a good option for someone looking for increased high-rpm performance. It is also able to sit comfortably under a factory C6 hood.
One of the highlights of the Holley intake is its build materials and construction. The Sniper is made entirely from 5mm T6061 sheet aluminum and is 100% TIG welded. This combination provides unparalleled reliability and strength. Due to the Sniper’s grade-A construction, it is a common option for LS builds featuring forced induction.
In addition to the manifold itself, the kit also comes with a compatible fuel rail that plugs directly into the runners. The Sniper manifold that we are suggesting here is designed to be paired with a 90mm throttle body, but Holley also offers the same manifold designed to be paired with a 102mm TB.
Overall, the Holley Sniper is a great option for those looking for a manifold with a shorter intake runner length than stock. The Sniper performs best in the higher rev range due to the shorter runner length which is good for those tuning for a high-end power band. However, it is important to note that it will sacrifice some low-end torque. A larger cam with the Sniper manifold is a commonly applied recipe and yields good results.
Chevy LS3 Intake Manifold Upgrade Summary
The Chevy LS3 is one of the most famous engines around for good reason. From the factory, it produces fantastic power in a nearly indestructible package. There are a few key standout characteristics of the LS3, but its factory flow figures and outstanding intake manifold design really highlight the attention to engineering that went into it. While the stock LS3 intake manifold is hard to beat, there are some great aftermarket options out there for those looking to dial in their power and torque curves or tune their LS3 intake for an upgraded cam or larger displacement.
The way that aftermarket LS3 intake manifolds are constructed plays a huge part in how the engine performs. Intake runner length is one of the most important factors, as that corresponds directly with where peak power and torque are produced. Shorter runners allow for better high-rpm performance while longer runners have a better low-mid rpm balance. Intake plenum size and shape also play a significant role in performance as it is related to air velocity and volume. Tuning an aftermarket intake to work with an upgraded cam is extremely important, as they need to work in unison for the best results.
If you enjoyed this article and are looking for additional Chevy 6.2L LS3 content, check out our Best Chevy LS3 Engine Upgrade Guide. As always, safe driving!
