5.7 HEMI Throttle Body Upgrade Guide: Best 345 HEMI TB Mods (2023)

The 5.7 HEMI is a solid engine out of the box, but it's certainly underpowered for its size. However, the 5.7-liter V8 is a capable engine with a few simple modifications. We wrote an article about this in the past.Top 5 Bolt-On HEMI Modsto really bring this engine to life. A 5.7 HEMI throttle body upgrade did not make it to this list. However, it's still a great upgrade that could offer decent gains and performance benefits. In this article, we look at 5.7 TB HEMI upgrades, spacers, performance upgrades, benefits, and more.

Shown above is Holly Sniper EFI 92mm throttle body (will not work with OEM intake manifolds)

What is a butterfly body?

A throttle body (TB) is positioned between the intake manifold and the intake manifold. The TB includes a throttle valve to control the amount of air entering the engine. Sensors in the throttle body transmit throttle position, allowing the engine to adjust other parameters such as fuel flow.

There are a number of other details and niceties to the throttle bodies. However, the main goal of TB upgrades is simply to increase the size and allow for more airflow. Therefore, the details of the operation of the throttle body and all sensors are not important for this topic.

Lastly, the 5.7 HEMI throttle body controls the amount of air entering the engine. In WOT, the amount of air is limited by the size of the TB reservoir. Upgrading to a larger throttle body can provide better throttle response and performance gains.

5.7L V8 Throttle Body Spacer

The focus of this article is on actual throttle body upgrades. But the 5.7 HEMI TB spacers are also a great topic. A throttle body spacer is a simple mod on the surface; it's literally just a ~0.5-1.0″ piece of metal that fits between the throttle body and intake manifold. However, many spacers also contain slots to create an air vortex. The easiest way to explain the design is to look at older engines.

In the past, most car engines used throttle body injection or carburettors. Air and fuel mixed further from the cylinder head. A slotted throttle body spacer can be used to create a swirl. This, in turn, resulted in better fuel atomization because the vortex effect of a slotted spacer allowed air and fuel to mix better. In fact, this leads to better performance and performance.

Many newer engines use multiport fuel injection, as is the case with the 345 HEMI. Spinning the air in front of the intake manifold does not contribute to fuel atomization because the intake manifold runners smooth the air before it reaches the ports. As a result, throttle body spacers aren't as useful on engines like the 5.7 HEMI compared to older carbureted engines.

Is a HEMI TB 5.7 spacer worth it?

It's unlikely to be worth the cost of a 5.7 HEMI throttle body spacer for most people. Some 5.7 liter V8s can extract 2 to 5 horsepower from a TB spacer. We would also argue that many will show no gains or even small losses in performance. Most of the gains or losses are likely to be attributed to natural fluctuations in WOT pulls. Also, there's no reason to think that a 345 HEMI throttle body spacer will increase MPG.

Throttle body spacers are a popular topic that often sparks heated debate. Some people believe they slightly increase performance, and for around $100-$150, they're worth a try. Others claim that TB spacers are nothing more than a paperweight and a scam. For engines with intake manifold injection, we tend to the latter.

Creating a "tornado" or vortex in front of the intake ports and right in front of the air/fuel mixture shouldn't help much. However, a slight increase in the intake plenum may be of little benefit. Adding power to NA engines like the 5.7 HEMI isn't easy unless you go for big mods like heads, cams, or forced induction. Anything helps, and we weren't going to blow them away by spending $100 to get a few extra horses.

5.7 Advantages of the HEMI throttle body

Benefits of upgrading the 5.7 HEMI throttle body include:

• 5-10hp pero
• similar torque gains
• better throttle response
• simple and cheap mod

The main reason to upgrade the 345 HEMI TB is performance. Power gains generally fall in the 5 to 10 horsepower range. Nothing spectacular compared to mods like a tune, headlines, or cameras. However, the performance increase from the 5.7 HEMI throttle body is solid considering it's an easy and inexpensive upgrade. Better throttle response is also a common benefit of a larger TB.

For more performance, the 5.7-liter V8s are likely to win out at the lower end of this range. Engines with overhead cams, manifolds, and/or forced induction will likely have higher gains. Some can even see 10+ horsepower with the proper mods and a properly sized TB.

TB 345 HEMI Size

If the idea is to increase airflow through the throttle body, bigger is better, right? Not quite. Choosing the correct throttle body size is important to maximize top-end gains without sacrificing low-end torque. Once the airflow requirements are met, increasing the size simply undercuts the low-end performance and provides no additional gain to the top.

The main diameter of the 5.7 HEMI throttle body is 80mm. With most stock engines all it takes is upgrading to something like the Fastman 82mm TB. This TB is actually 86mm in WOT due to a modified half shaft which adds an extra 4mm of airflow at full throttle. For headers, cams, or FI, you should probably consider something closer to 88-90mm at WOT.

Larger throttle bodies are usually overkill on the 5.7 HEMI unless you have an inboard motor. The point here is: don't go overboard with the 345 HEMI TB mods. Bigger is not always better and size should be dictated by your current or planned modifications in the near future.

Upgraded 5.7 HEMI Throttle Body Upgrades

With the basics done, it's time to move on to some of the best 5.7 HEMI throttle body upgrades. Please note that this is not an exhaustive list. There are a lot of great throttle bodies out there. Rather than an exhaustive list, let's focus on a few 5.7-liter V8 TB upgrades that offer an excellent balance of performance, price, and quality.

1) 5.7 HEMI Das Fastman TB-Update

Preis:$ 250-547

Buy here: 5.7L Fastman Throttle Body

The Fastman 5.7 HEMI throttle body is arguably the most highly regarded TB on the market. They are highly tried and true and one of the few brands that are consistently endorsed by others. Fastman uses the original throttle body and makes a number of modifications that produce excellent results. They offer 82mm and 84mm TB for the 345 Mopar engine. The throttle bodies, however, are 86mm and 88mm at full throttle due to a +4mm mid-shaft modification.

Both throttle openings are 85mm, tapering to 82mm or 84mm (depending on which TB you choose) at the main bore. Fastman charges $250 for TB mods, but no major fees apply. You will have to buy a new throttle body through them or send in your current one to save some money. However, this will require your HEMI 5.7 to be offline for a few weeks.

Ultimately, according to many, this is the best 5.7 HEMI throttle body on the market. It's really hard to go wrong with Fastman throttle bodies unless you're extremely modified and require something larger than 86mm or 88mm at full throttle. Even then, you probably don't need a bigger throttle body. Either way, if you're looking for the best of the best, the Fastman is a solid choice.

2) Dodge 345 HEMI BBK Throttle Body

Preis:$ 500-550

Buy here: BBK 5.7 HEMI TB-Upgrades

BBK is another popular brand for 5.7 HEMI throttle body upgrades. They are also known for other 5.7L V8 mods such as headers, exhausts, air intakes, and more. BBK offers 85mm and 90mm throttle bodies for the 345 Mopar engine. However, they recommend using 85mm for the 5.7 HEMI, while 90mm is better for the larger 6.4-litre engine.

We agree with this recommendation, especially for basic bolt-on HEMIs. However, if you have extensive performance mods, the 90mm throttle body might make sense. They're about the same price as The Fastman, so it all comes down to brand preference. However, the latter is cheaper if you're willing to ship the throttle body up front.

You can't go wrong with the BBK either. We think the Fastman 345 HEMI TB is the most respected and popular choice. However, BBK throttle bodies are great too. So if you are loyal to BBK, this is a great option.

3) EFI 92mm Sniper Throttle Body

Preis:223,95 $

Buy here: 5.7 HEMI Sniper 92mm Throttle Body

This throttle body takes us in a completely different direction than before. The Sniper EFI 92mm Throttle Body will not work with the stock intake manifold. Instead, it's a throttle body upgrade for the Sniper EFI pickup. We talked about this product in our article.5.7 HEMI intake manifold upgrades.

Upgrading the intake manifold and throttle body can be a great combination of mods to remove all at once. Replacing a 6.4 HEMI header is a popular option on the 5.7-liter V8. In this case, the 5.7 and 6.4 throttle bodies are interchangeable. However, true aftermarket trucks like the Sniper EFI may require aftermarket throttle bodies.

Again, this is a completely different direction, but something to consider before upgrading your throttle body. You may want an aluminum manifold if you want to add boost and it's typically not compatible with most TB mods.

5.7 HEMI Throttle Body Upgrade Summary

Throttle body upgrades didn't make it to our list of the top 5 HEMI 5.7L engine mods. Other upgrades such as tuning, heads, intake manifolds, and cams offer more compelling performance upgrades. However, a throttle body is still an excellent mod to maximize the performance of the 5.7L Mopar V8.

A big problem is the 5.7 HEMI throttle body spacers, but there is no convincing evidence that they provide consistent performance gains. They are more effective upgrades for older throttle body fuel injected engines. For less than $150, though, it might be worth squeezing in some extra horsepower.

Actual throttle body upgrades are where the real performance benefits can be seen. 5.7 HEMI TB mods can deliver 5-10+ horsepower, similar torque, and better throttle response. Solid benefits for a $500 upgrade that bolts directly to the intake manifold. Fastman and BBK offer some of the best throttle bodies for the 345 HEMI. If you plan on upgrading your intake manifold, you may want to forego a throttle body. Some manifolds require aftermarket throttle bodies that do not match the original manifold.