The Chrysler 6.4 HEMI made its debut in the 2011 Dodge Challenger SRT8 with 470 horsepower and 470 lb-ft. It’s since made its way into many other Chrysler, Dodge, and Jeep vehicles. Peak output comes in at 485 horsepower and 475 lb-ft of torque. Clearly, the 392 HEMI is no slouch from the factory. However, there’s still plenty of room on the table to squeeze out more power. In this article, I discuss some of the best 6.4 HEMI performance upgrades, power gains, cost, and more.
392 HEMI Differences
Before diving into the bulk of this article it’s important to discuss the few variants of the 6.4 HEMI. Chrysler came out with the 392 HEMI in 2005 and it was available as a crate engine beginning in 2007. It delivers 525hp and 510 lb-ft and is a very different engine from the production version. The two engines share few parts in common despite the same 392 cubic-inch displacement.
There’s also the truck version of the 6.4L V8. This shares nearly all parts in common with the standard engine in the SRT8 and SRT 392 models. However, the 6.4 HEMI in Ram trucks is re-tuned for better MPG and a power band for better towing performance. This version of the engine offers 366-410 horsepower and 429 lb-ft of torque.
Ultimately, the topics and upgrades in this article apply to both production versions of the engine but not the 392 crate motor. Fitment of parts and specific power gains may differ. The bulk of the information applies to all production 6.4L V8 HEMI engines, though.
5 Best 6.4 HEMI Performance Upgrades
Some of the best mods for the Dodge 392 engine include:
- Throttle body
The above list is our primary focus for 6.4 HEMI mods in this article. With the exception of cams, these are all simple bolt-on upgrades that offer great gains for the price. Cams are a bit pricier and more challenging to install, but they’re also likely the single biggest power mod outside of more serious upgrades like forced induction.
Anyway, throughout this article we will look at the above 5 best 6.4 HEMI performance upgrades in-depth. There are also plenty of other great upgrade; it’s simply too much to cover in one article so I narrowed it down to the 5 best basic bolt-on mods. However, at the end, I briefly discuss a few other awesome upgrades for the 392 HEMI.
1) 392 HEMI Tuning
While this list is in no particular order a tune is arguably the single best performance upgrade for the 6.4 HEMI. It’s not just about the power gains from the tune alone. Tuning is also the foundation to maximizing power gains from additional mods. As you begin adding more air and fuel it’s important to properly tune the computer (PCM) to account for the changes.
Adding a tuner to your 392 HEMI V8 offers the following benefits:
- Similar torque gains
- Bigger gains from additional mods
- Better throttle response
- Improved MPG
On a bone stock 6.4L HEMI you may only see power gains around 5-15whp with tuning. There is only so much power a tuner can squeeze out of a NA engine. Torque gains should fall in the same ballpark and you’ll likely notice better throttle and engine response. Depending on the specific tune you may also see better fuel economy. However, if you’re using the newfound power then that likely won’t be the case.
You will need a tuner device to flash the PCM. A tuner will run in the ballpark of $400-600 and often include some basic off-the-shelf tunes. Bigger power gains can be had with custom tuning the 6.4 HEMI, but that can add another $200-300+. Ultimately, a tune is a great upgrade as it’s relatively inexpensive for the power gains and helps improve performance from other upgrades.
Fueling is an important topic that ties into tuning the 6.4 HEMI. The biggest power gains with a 392 HEMI tuner will come from tuning for higher grade fuels. Most people likely only have easy access to pump fuels like 91 or 93 octane. However, if you have access to higher quality fueling then you may be able to pick up even more power.
Tuning for something like 100+ octane race gas will offer better power gains. E85 is also a great fueling option that you can find at some pumps around the US. However, E85 requires a lot of fuel flow so you’ll need some additional mods to run E85.
Long story short – tunes offer the best power gains with higher octane fuels (or E85). Tuning for 91 or 93 octane likely makes the most sense as it’s readily available. However, if you’re willing to deal with the hassles of better fuel then you can pick up even more power from tuning the 6.4L HEMI.
Tuner Price: ~$350-600 (+$150-300 if opting for custom tuning)
Tuner HP Gains: 5-15whp (20-30+whp possible with race gas or E85)
2) Intake Upgrades
Next up are cold air intake upgrades for the Chrysler 6.4 HEMI engine. An intake likely offers the most underwhelming power gains on this list. However, a 392 HEMI cold air intake still makes the list for good reason. Intakes are one of the cheapest performance mods and they’re incredibly easy to install.
Don’t expect to pick up much horsepower on a lightly modded engine (i.e tune only). However, intakes can offer solid power gains as you begin adding more upgrades and power. A few benefits of 6.4 HEMI intake upgrades include:
- Similar torque gains
- Improved throttle response
- Louder engine/exhaust note
The stock 6.4 HEMI intake flows fairly well for the intended power output. As such, you likely won’t pick up much power with an intake alone. However, as you begin adding mods like a tune, headers, cams, etc. then it’s important to have a better flowing intake. This is where you’ll likely start to see gains of 5-7+ horsepower from a cold air intake.
An intake can also help wake up the engine and exhaust notes from the 6.4L HEMI. It won’t be as drastic as exhaust or header mods, but it’s still a nice added benefit of intakes. We also think intake upgrades really help clean up the looks of the engine bay. Check out our 6.4 HEMI intake article for more info on cold air intakes.
Intake Upgrade Price: ~$200-400
Intake HP Gains: 3-7+whp
3) Throttle Body Mods
Again, this list of the best 6.4 HEMI performance upgrades is in no specific order. The throttle body (TB) is probably the biggest toss up on this list. Some believe it doesn’t make sense to upgrade the 392 HEMI TB unless you’re going with forced induction. However, an upgraded throttle body can be a great, inexpensive, and simple mod.
The Fastman throttle bodies are a great option if you do elect to upgrade. They use brand new throttle bodies that range from $192-210 for the 6.4L V8. Fastman charges $250 for the modifications to the TB along with $12 in shipping, so you’re looking at just over $450 all in. Benefits of a 6.4 HEMI throttle body include:
- 3-10wtq (a lot more possible on the low-end)
- Better throttle response
Peak power gains from a throttle body upgrade aren’t terribly enticing. On a bone stock car gains will be on the lower end of the range. However, you may pick up about 5-10whp peak with the rest of the mods like cams, headers, and tuning. A big improvement with throttle body mods is the throttle response and immediate torque.
In our opinion, we believe it’s best to save the throttle body for a later mod. It’s usually a great mod to combine with intake manifold porting which we discuss in the “other mods” section below. However, it can’t hurt to upgrade the 6.4 HEMI TB sooner. At less than $500 it’s a relatively cheap mod that’s also easy to install.
Throttle Body Price: $300-500
TB Power Gains: 3-10whp
4) 392 HEMI Upgraded Headers
Headers (also known as the exhaust manifold) is a lengthy subject since there are so many different options. Long-tube, shorty, catless, and high-flow cats are just a few of the important headers topics. We’ll do our best to summarize and get all the info in the limited space here. However, we also wrote an in-depth 6.4 HEMI headers guide so be sure to check that out for all the details on header upgrades.
Anyway, headers offer some of the best power gains for the 6.4L V8 HEMI. If you’re looking to build a powerful 392 HEMI then headers should definitely be towards the top of the mod list. The main goal with headers is to improve exhaust gas flow and reduce back-pressure. Since the exhaust manifold bolts directly to the engine it offers the biggest gains of any part of the exhaust system.
Benefits of 6.4 HEMI header upgrades include:
- Louder, aggressive exhaust sounds
The peak horsepower gains alone are impressive. However, it doesn’t end there. It isn’t always true that headers trade off low-end torque in favor of top-end power. In fact, a well designed set of long-tube headers can offer great gains throughout the entire power band.
Look to pick up about 10-20whp on lightly modded 392 HEMI engines. With the full list of bolt-on mods headers can deliver even more impressive gains of 20-30+whp. Headers also really wake up the sound of the 6.4 HEMI. Yet another benefit on top of the massive performance gains from a set of headers.
Catless vs High-Flow Headers
A set of long-tube headers will delete the OEM catalytic converters on the 6.4L Mopar engine. Fully catless headers will generally offer the best top-end performance. However, catless headers are technically illegal in all states and you’ll be unlikely to pass any form of emissions testing.
That’s where headers with high-flow cats come into play. You’ll still see massive power gains with a high-flow option and it should allow your 6.4 HEMI to pass emissions testing. Unfortunately, catalytic converters are expensive so high-flow headers will often run at least $300-500 more expensive than catless options.
As a side note – shorty headers will retain the OEM cats. However, shorty headers don’t offer performance gains quite as impressive as long-tube options. Expect to pick up closer to 5-15whp with a quality set of 6.4 HEMI shorty headers. The good news is that shorty headers are much cheaper, so it may be a good option if you’re looking for something modest.
392 HEMI Headers Cost: ~$400-1,500+
392 HEMI Headers HP Gains: 10-30+whp
5) Camshaft Upgrades
Last but certainly not least are cam upgrades for the 6.4L Mopar engine. This is the most expensive and complicated upgrade on the list, but cams are here for good reason. As with headers, there is a ton to unpack and discuss with cam upgrades. This is the short version, so check out our in-depth 392 HEMI cam upgrade guide for more.
Benefits of camshaft upgrades for the 6.4L V8 include:
- Massive 30-60+whp gains
- Awesome sounds
A proper set of camshafts can deliver insane 30-60+whp gains on the 6.4L HEMI. That’s about as good as it gets without adding even more expensive and complex mods – like a supercharger. Torque gains are also impressive with the right cam upgrades. Exact gains can vary and some cams may sacrifice low-end torque in favor of bigger top-end performance. Cams also sound amazing on the 392 HEMI, in our opinion.
Camshaft Upgrade Cost
The real downside to cams is the cost and complexity. Most casual DIY’ers can accomplish mods like an intake, tune, throttle body, etc. with relative ease. Cams are a totally different ballgame, so you might find yourself at a shop for the install. It can take 10-15 hours even for an experienced mechanic.
A set of 6.4 HEMI upgraded cams can run about $500-2,000 alone. If you opt for just the cams it will be on the cheaper end of the range. However, it’s a good idea to do it right and get a full package with valve springs, seats, retainers, pushrods, etc. This is where you’ll end up closer to $1,500 or higher.
If you’re having a shop do the work you’ll likely be out another $1,000-2,000. Ultimately, upgrading the 392 HEMI cams can easily run into the $2,500-4,000 ballpark if you aren’t doing the work on your own.
Cam Cost: $500-2,000 (+ $1,000-2,000 for install)
Cam HP Gains: 30-60whp
Other 392 HEMI Performance Mods
With the primary mods out of the way let’s move onto a few of the honorable mentions. We believe the above list of 6.4 HEMI performance upgrades offer the best balance of price, power gains, and simplicity. Tons of other great mods exist, though. This still isn’t an exhaustive list, but these are a few of the runner-ups.
1. 6.4 HEMI Forced Induction
Superchargers and turbos are where you’ll find the biggest possible gains. With forced induction it’s possible to push the engine to 1,000+whp. There are also “modest” setups for more reasonable 600whp, 700whp, etc builds. Ultimately, no matter your goals, forced induction is the recipe to building an insane 6.4 HEMI.
This could absolutely make the list of the best 6.4 HEMI upgrades. However, there’s so much to cover when it comes to superchargers and turbo kits. There are also a lot of other considerations like internal engine upgrades, fueling mods, and so much more.
It’s a very expensive route to go and there are too many details to discuss in one article. Both good reasons as to why superchargers and turbos didn’t quite make the list of best 392 HEMI mods. Fortunately, we also have a complete 6.4 HEMI supercharger guide for those looking to learn more.
2. Intake Manifold Upgrades
Intake manifold upgrades for the 6.4L HEMI are another great mod that could have easily made the above list. The most common upgrade is simply porting the stock 392 HEMI manifold. With porting you will generally see gains in the 5-10whp ballpark.
It runs about $400-600 to have the stock manifold ported. The downside is, you’ll likely need to send in your manifold upfront so your 6.4 HEMI will be out of commission for a little while. Some places sell new ported intake manifolds but that will set you back an extra $400-500.
Ultimately, porting the 392 HEMI manifold is an awesome upgrade. We still believe the top 5 upgrades are a better starting point and would save the intake manifold until the rest is done.
3. Exhaust Upgrades
Yet another upgrade that could have easily made the primary list of 392 HEMI performance upgrades. The options for exhaust upgrades are endless. We split headers into it’s own category since that’s where the biggest power gains come from the exhaust system.
Looking at the rest of the exhaust from the headers back you likely won’t see massive power gains. It’s still possible to pick up an extra 3-7whp. However, those are pretty small gains compared to a set of headers.
If you’re looking for a louder, more aggressive exhaust note then modding the rest of the exhaust is a great choice. The small power gains are just an added benefit. However, if you’re just looking for horsepower then there are better places to spend the money.
6.4 HEMI Performance Upgrades Summary
The 6.4 HEMI is a great engine that delivers solid performance from the factory. However, the large 6.4L V8 still has plenty of untapped potential. A few upgrades can really wake up the Mopar engine and take things to the next level.
A tune and intake are a great starting point. Headers and cams are a bit more expensive and complex, but they offer massive power gains. Upgraded throttle bodies, intake manifolds, and exhausts are also great additions. Of course, forced induction has huge potential but comes with a large cost and other risks and considerations.
Ultimately, the 5 best upgrades discussed in this article can push the 6.4 HEMI to 500+whp. That’s pretty impressive performance while remaining naturally aspirated. Add quality fueling and a few other bolt-on mods in the mix and 525+whp isn’t an unrealistic goal all while remaining naturally aspirated.
What mods have you done to your 392 HEMI? Are you considering any?
Leave a comment and let us know!