Exhaust Manifolds VS Headers | How Much HP Do Headers Add
What is the Difference Between Headers and Manifolds
Headers are cool. From the earliest days of hot rodding, adding a set of tubular headers (and ditching the stock exhaust manifolds) was a relatively cheap and easy way to add some power, change the exhaust note, and earn some street cred. Pick up a copy of Hot Rod Magazine from the 40’s through the present day and you’re going to see a hot rod, muscle car, or classic truck with a set of headers bolted up.
What are headers on a car? Generally speaking, headers are made from round tubing and allow the exhaust gases exiting the chamber through the exhaust valve to flow more freely, thus making more power. Exhaust manifolds, on the other hand, are generally cast and usually fitted to factory engines where ease of production and compact packaging are priorities. But that doesn’t mean that those stock manifolds or aftermarket performance manifolds are bad. In fact, there are advantages and disadvantages to each, and the purpose of this article is to discuss these differences and help you make the right choice for your car.
Different Types of Headers
Almost a century of engineering, innovation, and old-fashioned trial and error has led to a wide variety of designs for car headers. Most typically, a header is fabricated from mild steel or stainless tubing that is bent to clear chassis components and welded to a flat flange that bolts to the cylinder head. The most common types of headers for cars with V8 engines are “4 into 1” headers, where the four pipes from one bank meet at a single collector.
Anything that handles the flow of air, fuel, and gas into and out of the combustion chamber needs to be “right sized” for the engine. Think about putting a 1,050 cfm Dominator carb on a stock 305 engine. Performance will suffer because the carb is not compatible with the engine. Same goes for the headers, and one of the main factors that will affect a header’s performance is the diameter of the primary tubes and collector. Just like that Dominator on the 305, a small displacement, low rpm engine will actually suffer from a loss of drivability if a pair of headers with 2 ¼” primaries and a 4” collector are bolted up. Likewise, a high-rpm, large displacement engine will need plenty of volume in the header tubes to handle all the exhaust gases, so a small diameter, short-tube header will be a tremendous restriction and cause a significant loss of power across the board.
When a lot of us picture headers on a car, we’re picturing the old school long tube header. What are long tube headers? Long tubes have primary tubes that extend from the cylinder head all the way down to collectors below the floorboards. Sometimes there’s not enough space or ground clearance for this design, so “shorty” headers are a popular alternative. Most shorties are still a 4-1 design, but the collector is moved up either right under the center two exhaust ports or just behind the rear exhaust port on a V8. Shorty headers work well in applications where space is extremely tight or on lowered cars where there’s not room for a collector under the floorboards. However, when it comes to long tube headers vs shorty headers, the shorty design will almost always make less power due to the limited volume and unequal length of those short primary tubes.
Yet another header design is the 4-2-1, or “Tri-Y.” These are so named because the merging of the primary tubes occurs in a series of three “Y” shapes. First, the four primary pipes merge into two, then those two merge yet again into one larger collector. Compared to the more common 4-1 header, Tri-Y’s can offer a marginal increase in low to mid-range power. In contrast, 4-1 headers vs 4-2-1 will tend to have less back pressure and flow better at high rpm, moving the powerband up slightly and offering softer performance at low rpm.
Different Types of Exhaust Manifolds
All manifolds are not created equal. Many of us think of those rusty old stock manifolds laying in the corner of the garage with broken studs and all the aesthetic appeal of a hole in the ground. However, there are plenty of good manifolds out there, and some were even designed to offer some of the performance of a header with the trademark low maintenance of a cast manifold.
Log manifolds are the most common factory manifold design. Short sections from each cylinder merge into a long, straight section with a collector at the rear. These were cheap to produce, are compact, and generally aren’t going to support a ton of power.
Other factory designs are actually capable of making some horsepower. The famous ram’s horn manifolds, most typically seen on early small block Chevys, have longer runners and pair the cylinders together to reduce backpressure. Performance variants were used on Corvettes and other factory hot rods that have larger passages and 2 ½” collectors. When considering the large ram horn manifolds vs. headers, in particular short tube headers, it’s fair to think of both as having similar performance potential on a relatively mild street engine.
In rare cases, stock manifolds were designed with high performance in mind. The stocker and muscle car wars of the 60’s brought us such anomalies as the bonkers Chrysler Max Wedge manifolds, Chevy’s “Mystery Motor” manifolds, and Pontiac Ram Air manifolds. These manifolds are rare and hard to find, but have an undisputable cool factor.
The performance aftermarket has also stepped up the manifold game with high flow manifolds that deliver the best of both worlds. They combine the low maintenance and nearly indestructible nature of a cast manifold with enlarged runners and big collectors to improve performance. When choosing between these high flow manifolds and headers, performance manifolds are likely not going to make as much power as a properly sized long tube header, but they can be a great compromise in certain situations.
Headers vs Exhaust Manifolds
So, which choice is right for you? There are several factors at play here, but the first one needs to be a careful look at the logistics of your project. Manifolds are almost always more compact. Headers need some space as the tubes bend and turn through the chassis. Stock manifolds were designed by the OE’s to be packaged into a wide variety of chassis, so they’re more likely to fit and clear everything, especially in cars where space is tight.
Manifolds also typically require less maintenance. Headers have long had the reputation for flanges that warp and leak as well as collectors that get bashed on something and start leaking. Manifolds on the other hand were designed by the OE’s to be maintenance free for thousands of miles. It should be noted, however, that many headers have started using thick 3/8” flanges and collectors with lower maintenance couplings like V-bands. This has gone a long way toward mitigating the old leaky header bugaboo.
The real benefit of headers is the performance. The huge variety of tube diameters and lengths of headers means that you can usually find the perfect performance complement to your engine. And let’s be honest, they look cool. Headers are almost always a good addition to muscle cars old and new for the cool factor, if nothing else.
Another thing to think about when shopping for headers is fitment to your engine and chassis. Common Chevy applications like Chevy 350 headers and big block Chevy headers are widely available for many chassis. Same for Ford, with headers for a 460 Ford, Ford 302 headers, and 351 Windsor headers available from most header manufacturers. Common chassis, like most muscle cars from the Big 3 as well as truck applications like C10 headers, usually have multiple engine options covered by aftermarket tubular headers. Even if you’re doing a swap to a different engine platform, common swaps like LS swap headers for G-body and S10 V8 headers are usually covered with off the shelf parts. If you’re doing something completely unique, you may need to consider a custom header kit that will allow you to build your own headers.
Headers vs Manifolds Sound
This is an important one. The way our cars sound is as critical as choosing the right wheels or paint color. Headers and manifolds have a distinctly different sound, but the way they affect the tone at your tailpipe will depend on the engine and the rest of the exhaust system like muffler sizing, etc. However, here are some general characteristics to keep in mind.
First, manifolds. Most manifolds pretty quickly dump each cylinder into a common passage, so pops, cracks, and pulses from the individual cylinders get smoothed out. The result is a deeper, more subdued sound. Manifolds through performance mufflers typically generate a satisfying “burble” on V8 engines that might just be more tolerable than an aggressive header tone during routine driving.
Headers, on the other hand, keep the exhaust pulses from the individual cylinders separate for longer. The resulting sound is generally “sharper,” both at idle and on the throttle at higher engine speeds. Headers don’t really smooth out those snaps, crackles, and pops during decel and overrun, which typically results in a more aggressive exhaust note. Want your hot rod to sound like the hero car in a movie? Headers are right for you.
How Much HP Do Headers Add
Will headers add horsepower? Adding tube headers on a car can provide a noticeable increase in horsepower and torque compared to stock exhaust manifolds, but the key word there is can. Just bolting on a set of headers to an otherwise stock engine will not instantly transform your car into a tire fryer. The exact gain varies depending on several factors such as the engine's displacement, compression ratio, camshaft profile, and overall engine tune. To make an extreme generalization, aftermarket headers can yield anywhere from 5 to 20+ additional horsepower, with larger gains seen in heavily modified, high performance engines that are moving a lot of air and a lot of exhaust gas out of the chamber. How much horsepower do long tube headers add? The answer here is very much the same. Almost all engines will benefit from the reduced backpressure of a long tube design, but how much power and where it is in the powerband will depend on those same internal factors like cam profile, displacement, and cylinder head design.
When discussing headers for cars, performance exhaust systems, and answering the question of do headers add horsepower, the terms “backpressure” and “scavenging” usually come up. Both principles are at the heart of the performance gains seen when upgrading exhaust components, particularly headers. Backpressure is resistance in the exhaust system to the exiting exhaust gases. The piston is pushing the exhaust out of the exhaust valve and into the exhaust system. A restriction in the system means that the piston is exerting more energy to expel the mixture. This lost energy equates to a loss of power and engine efficiency. Headers generally create less backpressure when compared to a stock exhaust manifold.
In addition to decreased backpressure, scavenging is another key mechanism behind the horsepower increase from headers. This occurs when exhaust gases exiting the engine create a vacuum or low-pressure zone in the exhaust pipes, which helps draw exhaust gases out of the combustion chamber more efficiently during the exhaust stroke and can even help pull more of the air/fuel mixture into the chamber through the intake side. By promoting better scavenging, headers reduce backpressure and improve exhaust flow, allowing the engine to breathe more freely and generate additional power. Improved scavenging is one of the key benefits of long tube headers.
While most of this article is discussing what’s the difference between headers and manifolds generally, it’s worth mentioning that some of the concepts here change when talking about late model cars. Questions like “will headers void warranty” and “do long tube headers require a tune” come up when discussing newer cars and late model swap applications like LS headers, and the answers will vary depending on the year and type of car. Generally, cars with EFI will benefit from tuning tweaks to take full advantage of the header’s performance potential. As for warranty and emissions concerns, it’s best to check with your local authorities or dealer to keep out of trouble.
Like most mechanical principles, applying the proper mathematic equations allow us to quantify things like what do long tube headers do and unequal headers vs equal length. These equations are commonly used in exhaust system and headers and exhaust manifold design. They factor in variables like exhaust gas temperature, gas density, tubing diameter, and engine RPM to calculate the ideal length of tubing and scientifically answer the question will headers increase horsepower for a highly specific application. Check out our exhaust pipe size guide for some practical tips.
Shorty Headers vs Stock Manifolds
Are shorty headers worth it when compared to manifolds? When it comes to shorty headers vs manifolds, the line starts to get a bit blurry. The real benefit of each when compared to long tubes is compact packaging, but the compact nature of the shorty tube headers compromises performance and power potential, which is the real benefit of a header. Generally speaking, even short block hugger headers will flow better than a stock manifold, but not nearly as well as a header with longer tubes. So, the real decision in this case largely comes down to aesthetics and cost. A nice new set of shorty headers is going to look better than your rusty old manifolds and may offer some small improvements in the sound and power department.
Equal Length Headers vs Unequal
In addition to diameter, the length of the primary tubes can have a big impact on performance. So, are equal length headers better? If space allows, headers with tubes of equal length for each cylinder will generally perform the best. The key to an equal length headers horsepower gain is that they are designed to ensure that all exhaust pulses reach the collector at the same time. This optimizes exhaust scavenging and makes more power. Equal length headers are almost always going to be better, but this can be hard thing to do if space is a concern. Sometimes, you have to compromise when tubes of unequal length are the only way to get the header to fit.
Speaking of space constraints, what about denting headers? If we’re being honest, most of us have bashed a header tube with a ball peen at least once in search of some clearance to a steering box or framerail. As you would expect, this is best avoided since it creates a restriction in the tube and can limit the flow of exhaust gases. Maybe even more impactful is the turbulence that the dent can cause. Exhaust wants to flow smoothly, and when it hits a bump like that dent you just smacked into the primary, it will start to swirl and slow down, creating even more restriction.
Painted Headers vs Ceramic
Here we have another issue that has plagued headers from the beginning. It’s hard to come up with a coating for something that heats up to more than 1,000 degrees, then cools down to ambient temperature, over and over and over. There’s a reason those old headers at the swap meet are covered in rust and flaky old paint.
In the past few decades, improved header coatings have emerged that are fortified with ceramic to be more resistant to repeat heat cycles and extreme temperatures. But they come at a cost. Having your headers coated or buying a new set that are already coated will add significant expense to the tab. But the return on that investment is a long-lasting coating that can be maintained just like the other finishes on your car to look great for a long time. For more on this, check out our article on how to clean headers. Ceramic coatings also act as a thermal barrier, keeping less of the exhaust heat from dissipating into the rest of the engine compartment and heating up things that you don’t want heated, like coolant and fuel. Note that another option to control exhaust heat is header wrap, which can be a tricky thing to do well. Our article on how to wrap a header will help you get started.
Painted or raw mild steel headers will typically be cheaper than coated headers, but the coating will almost always be a short-term solution. High heat exhaust paint is readily available, but is far more likely to fail after a relatively short period of time than full ceramic coatings. However, header paint is available in a variety of colors, so if you feel like making a statement or are looking for a retro vibe with white or red headers, paint will get you there. Just be prepared to re-paint with some regularity.
Of course, we also have to mention stainless steel. While this is generally the most expensive option, headers made from stainless will stand up to the heat cycles without having a coating to fail. Instead, depending on the alloy, stainless will turn a straw color that can be polished out for many miles of good-looking performance.
Headers Long Tube vs Shorty vs Exhaust Manifold | Pros & Cons
There’s a lot to consider when it comes to headers vs manifolds pros and cons. Are headers worth it for you? What types of headers will work best on your car? If all the options have you scratching your head, the chart below will give you another way to look at the benefits and disadvantages of long tubes, shorty headers, and manifolds.
Once you’ve figured out what design is right for your car, check out the header and manifold options from Speedway Motors and brands like Hooker headers, Patriot headers, Flowtech headers, and Dynatech headers.
