The 6.1 HEMI Intake Manifold Upgrade Instructions. We recently looked at the 6.1 HEMI engine that was used in different SRT8 badged automobiles from 2005 to 2010. Depending on the model, they produce 420-425 horsepower and 420 pound-feet of torque. Despite this, some people believe they are underpowered from the factory, especially given their enormous 6.1 liter displacement. We already discussed upgrading to a supercharger for the 6.1 HEMI, and now we’re going to look at 6.1 HEMI intake manifold improvements.
This guide will teach you everything you need to know about upgrading the intake manifold on your SRT8 powered by a 6.1 HEMI. We’ll go through how intake manifolds function, the advantages of upgrading, and why you should consider updating your throttle body at the same time. Finally, we’ll share our favorite picks for 6.1 HEMI intake manifolds on the market today.
What is the purpose of a 6.1 HEMI Intake Manifold?
Let’s start with the fundamentals: what is an intake manifold and how do they function? The intake manifold is in charge of providing fuel and air to an engine. They are located between the throttle body and the cylinder head(s) and receive their air supply from the throttle body’s air intake. Fuel is delivered through fuel injectors located in the intake manifold.
An intake manifold is made up of two major components: the plenum and the runners. The plenum is the top section of the intake manifold, and it typically resembles a huge cylinder or box. The runners are tiny tubes that attach onto the cylinder head and are connected to the plenum. Most manifold designs have one runner per cylinder, hence the 6.1 HEMI has eight runners.
The function of an intake manifold is to deliver air and fuel uniformly and fast into all of the cylinders. Air is drawn through the throttle body and into the plenum, where it goes down the individual runners and into the combustion chamber via the cylinder head(s). It mixes with fuel provided by fuel injectors on its route into the combustion chamber.
Each runner of the intake manifold has its own butterfly valve to regulate air exiting the runners. These open to enable air to pass through and seal to prevent air from passing through.
What materials are used to make HEMI intake manifolds?
When it comes to Gen III HEMI intake manifolds, there are a few basic materials to choose from. Cast iron, cast aluminum, billet aluminum, and composite plastic are the most common materials used to make manifolds. Each has perks and cons.
Cast iron manifolds are inexpensive and long-lasting, but they are also heavy and have poor flow. Cast aluminum is lighter and flows better than cast iron, but it is less durable. Sheet metal (billet aluminum) flows somewhat better than cast aluminum but is more expensive. Composite plastic is lighter and less expensive than aluminum, but it is not as durable.
The intake manifold on the stock 6.1 HEMI is comprised of cast aluminum. The majority of aftermarket 6.1 HEMI intake manifolds will be cast or billet aluminum, or potentially composite plastic. Billet aluminum manifolds, also known as sheet metal manifolds, have grown in favor in recent years due to their low cost and excellent flow.
Styles of HEMI Intake Manifolds
Aside from material, another factor to consider with intake manifolds is runner length and plenum volume. Many people believe that simply installing the largest plenum with the longest and broadest runners will result in the best air flow, however this is completely incorrect. In reality, you want a plenum and runners that work together to provide the finest pulse reversion control possible.
Without getting too scientific, pulse-reversion is a phenomenon that can occur in any intake manifold. When the intake manifold runner’s butterfly valve opens, air enters the engine. When the valve is closed, the air has nowhere to go and piles on top of itself. This generates a high-pressure wave that flows back up through the runners and into the plenum.
The high pressure wave is driven back down the runner once it reaches the plenum. If the runners and plenum in the intake manifold are properly sized, the wave of high pressure should be sucked into the combustion chamber before the butterfly valve closes again. Because the high pressure wave hits at precisely the proper time, this also has the effect of forcing more than usual into the engine. If it doesn’t, several waves of high pressure will build up, causing air turbulence and poor flow.
Other factors influencing runner length are related to the power curve. Longer and narrower runners often produce greater low-end power, whereas shorter and wider runners produce more top-end performance.
What is the best Intake Manifold for me?
The sort of manifold you choose will be determined by your power objectives and intents (street use, autocross, track use, drag racing, etc.). Longer and narrower runners might be more fun on the street and track, whereas wider and shorter runners would be ideal for drag racing.
6.1 Advantages of Upgrading Your HEMI Intake Manifold
The following are the primary advantages of upgrading the 6.1 HEMI Intake Manifold:
- 5 to 20 wheel horsepower and torque
- Weight reduction over the original manifold
- Increased air flow through the stock manifold
- Boosted engine volume/noise
- Appeal to the eye
Upgrading your 6.1 HEMI intake manifold has various advantages. The first and most noticeable will be power gains ranging from 5 to 20 wheel horsepower and torque. This will be due to an aftermarket manifold’s increased airflow and plenum volume. Other supporting upgrades, such as a cold air intake, throttle body, and long-tube headers, will result in more gains than a standard engine.
Other advantages include reduced weight, greater engine noise/volume, and improved visual appeal. The factory 6.1 HEMI intake manifold is cast aluminum and weighs around 65 pounds. Aftermarket manifolds typically weigh less than stock, particularly sheet metal aluminum, which can reduce weight by up to half.
Installing an intake manifold will also increase the volume of your engine. The extra air and lack of insulation will make it much more noticeable, similar to a larger intake or throttle body. Finally, a beautiful aftermarket intake manifold will surely make your engine bay look cleaner than the factory one.
Enhancing the Throttle Body
When many individuals replace their intake manifold, they also replace their throttle body. This is not required, although it has advantages. A larger throttle body allows more air into the engine, resulting in higher power. However, the stock unit will enough for the majority of applications. However, keep in mind that some intake manifolds require a larger throttle body, which means you’ll need a new air intake.
The factory throttle body is 80mm, while aftermarket versions reach over 100mm. If you want to boost your 6.1 HEMI with a turbocharger(s) or a centrifugal supercharger, modifying the throttle body is usually a smart idea to accommodate the increased airflow. assuming you keep it naturally aspirated and under 700 horsepower, the stock unit (assuming it fits) will suffice.
The 6.4 HEMI Intake Manifold Upgrade
Instead of going aftermarket, several 6.1 HEMI owners have swapped out the intake manifold for the larger 6.4 HEMI. The 6.4 HEMI intake manifold is made of composite plastic rather than aluminum and features twin active runners. This enables the manifold to optimize torque and horsepower across the power spectrum by using variable runner lengths.
The active runners on the 6.4 HEMI, on the other hand, switch from long to short at around 4,800 RPM. If you switch over the 6.4 intake manifold, you’ll need to find a way to activate the switch in order to get the full benefits of the manifold. Many individuals have chosen to acquire a used 392 HEMI intake manifold rather of a new aftermarket 6.1 intake manifold since it is less expensive. Nonetheless, a correctly sized 6.1 aftermarket manifold will almost certainly be superior.
Upgrades for the 6.1 HEMI Intake Manifold
The following are the top four 6.1 HEMI Intake Manifold Upgrades:
- Stock manifold with porting
- EFI Holley Hi-Ram
- Sheet Metal Holley Sniper EFI
- EFI Edelbrock Victor
These are the top four choices for modifying your 6.1 HEMI’s intake manifold. The aftermarket for the 6.1 HEMI intake manifold is limited, leaving you with the option of porting the standard unit, Holley, or Edelbrock. Still, these are all good units with their own distinct advantages, which we’ll discuss further below.
1) Stock ported 6.1 HEMI intake manifold
The first suggestion is to port the stock 6.1 HEMI intake manifold. Porting is a viable choice for a variety of reasons. For starters, it is by far the most affordable option. While you can send it to Modern Muscle to have the manifold ported, that is the most expensive option at $649.00. Depending on your region and local market, local performance and machining shops should be able to port your intake manifold for roughly $300.
Porting is the process of smoothing and honing the inside of the throttle body to remove any roughness, defects, or constraints that may obstruct airflow or cause excessive air turbulence. It’s a simple method that will offer you power boosts ranging from 5 to 15 wheel horsepower on its own.
Porting is a popular choice not just for its inexpensive cost and power improvements, but also since most aftermarket units will not produce much more horsepower. Getting 5-15 wheel horsepower out of a manifold is a significant improvement, and most aftermarket devices will only add 5 wheel horsepower at most.
Porting the OEM unit is probably your best bet unless you plan on running forced induction and boost through a turbocharger(s) or centrifugal supercharger(s). It keeps OEM fitment and will produce comparable power improvements at a considerably lesser cost. It will, however, be heavier than an aftermarket manifold.
2) SRT8 Holley Hi-Ram EFI Intake Manifold
The Holley Hi-Ram EFI intake manifold for the 6.1 HEMI is next on our list. Holley has long been regarded as one of the top brands in HEMI performance, and its intake manifolds are highly regarded and recommended.
The Hi-Ram EFI intake manifold is cast aluminum with lengthy runners. It will be useful for producing low-end power and has nitrous nozzle installation pads. The manifold is somewhat high in the engine compartment, hence the name, but it appears to be extremely clean. It is suitable for both naturally aspirated and forced induction engines.
The throttle body inlet is 95 mm, which is significantly larger than the stock 80 mm. Importantly, some hoods may have clearance concerns with this intake manifold, thus it is recommended for those doing a HEMI switch. Stock hoods will very certainly need to be modified.
3) SRT8 Holley Sniper EFI Sheet Metal Intake Manifold
The Holley Sniper EFI Sheet Metal 6.1 HEMI Intake Manifold is the third item on our list. The Sniper line of intake manifolds is quite popular and well-reviewed in many applications, not just HEMI.
The Sniper features a lower profile and shorter and wider runners than the Hi-Ram. Because it is made of sheet metal, it will be lighter than the Hi-Ram and stock units. The sharpshooter is made of strong metal for strength, and the runners have tapered tops to maximize air velocity and dispersion.
The Holley Sniper has a throttle bore of 90 mm, which is 5 mm narrower than the Hi-Ram. The stock 80 mm throttle body, like the Hi-Ram, will not fit without modification. The Holley Sniper should fit under stock hoods and provide similar 5-20 wheel horsepower improvements as the Hi-Ram.
4) Edelbrock Victor EFI SRT8 Intake Manifold
The Edelbrock Victor 6.1 HEMI intake manifold is our ultimate suggestion. Edelbrock is one of the most famous firms in the performance market, and they have been producing parts for muscle vehicles since the 1950s and 1960s. For decades, they have been well-known for their carburetors and intake manifolds.
The Edelbrock Victor EFI intake manifold resembles the standard model but flows significantly better. It has longer running runners and relocates the fuel injector bosses for maximum flow. The Edelbrock, unlike the Holley alternatives, can use the stock 80 mm throttle body without modification.
The manifold is constructed of cast metal and has a black powder coated finish. The Edelbrock will pass OEM hoods without issue, however it will require a fuel rail kit to be installed alongside it owing to the injector relocation. Although it is a little pricy, the Edelbrock is definitely the best bet for those wishing to add forced induction to their factory 6.1 HEMI.
6.1 Summary of the HEMI Intake Manifold
You have a lot of decent options if you want to upgrade the intake manifold on your 6.1 HEMI. Upgrading (or porting) your intake manifold will enhance horsepower and torque, reduce superfluous weight, increase airflow, increase engine volume, and improve the appearance of your engine bay. Intake manifolds will not add outrageous amounts of power, but the difference will be evident.
Most folks will find that porting their stock intake manifold is the best solution. It will provide comparable improvements to an aftermarket unit while keeping factory fitment and throttle body. The Edelbrock Victor manifold is an excellent choice if you intend to boost your 6.1 HEMI powered SRT8 with a turbocharger or centrifugal supercharger. It has longer runners than the factory model and can accommodate a larger throttle body.
If you’re doing a HEMI switch, you’ll most likely be looking at one of the Holley alternatives, the Hi-Ram or Sniper. Both are good options, with the Sniper being more expensive and having a lower profile than the Hi-Ram.