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Headers VS Exhaust Manifolds: Which is Best for Your LS Swap?

Author: Bradley Iger | 10/09/2020 < Back to Motor Life Home
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Since the dawn of hot rodding, swapping out exhaust manifolds for a set of tubular headers has been one of the go-to mods for those seeking a bump in horsepower along with a livelier engine soundtrack. But despite the benefits offered by headers, they’re not always the best solution for a given use-case.  


“From an OEM standpoint, for instance, you’re looking at both the cost to manufacture as well as fitment issues,” says Holley’s Luke Embry. “Making headers is more labor intensive – you can’t really cast a header, so that’s usually going to be a hand-built piece. And with exhaust manifolds, you’re also not really dealing with the same limitations in terms of bend radiuses and things like that, so you can fit a manifold into really tight spaces where a header might not work.”


And while the efficiency advantages of a tubular header are undeniable, exhaust manifold design has come a long way since the heyday of the muscle car. That’s one of the reasons why companies like Hooker offer both. Here we’ll take a closer look at the potential pros and cons of each option to help you determine which makes the most sense for your project.


While headers always win the outright power race, they're often not the best solution for every swap. Exhaust manifolds can be an affordable, durable, and space efficient solution for many builds.


Different Components For Different Applications


When it comes to choosing between headers and exhaust manifolds, Embry notes that the same factors faced by OEMs apply to aftermarket projects as well, but it also goes deeper than that due to the array of additional variables involved.


“There’s a notable cost difference between a manifold and quality header, but one of the biggest considerations here is often the ease of installation,” he says. “With a manifold, bolting it up is usually a pretty straight-forward install that can be done in a few minutes. And in some applications, a long tube header is going to be a totally different situation.”


He cites an as-yet unannounced manifold for late model truck applications as an example. “This is something where you can literally stick it through the wheel well and bolt it on – it’s going to take about ten minutes to get this manifold on once you have the old component off. But the long tube header we built to fit these trucks – which we designed to be as tight and compact as possible – requires that you take the transmission out of the truck to get the header in because it’s such a tight fit. I’m all about a set of long tube headers, but in some applications, the manifolds really end up being the best option.”


As you can see, these headers are a snug fit in this Mopar engine bay. They require fiberglass insulators to keep the plug wires from burning and the tubes are very close to the steering linkage.


Going LS

 

When it comes to LS swaps, extra clearance tends to be even harder to come by in engine bays that were never designed for GM’s modern small-blocks. And that’s one of the reasons why Hooker Blackheart exhaust manifolds continue to be a popular choice for folks who’re retrofitting LS power into older machines. These manifolds are designed to hug close to the engine block, allowing them to accommodate a wide variety of replacement and engine-swap applications.


“There’s nothing on the market that is tucked as tight to the block as these manifolds are,” Embry explains. “If you were to try to use the factory manifolds that come on, say, a fifth gen Camaro or something like that, you might have to cut the frame because the collector turns the wrong way, or make some kind of modification along those lines to get it to work. When we designed the Hooker Blackheart cast manifolds, we test fit them in numerous applications, and made sure that we got the collector outlets turned to the sweetest spot possible to make these work across many different applications.”

In the world of LS engines, exhaust manifolds are a lot more common because they flow well, package nicely, and rarely, if ever, have sealing issues. Hooker makes a high-flow exhaust manifold that packages tightly in swap applications.



Some combination are such a tight fit that going with a manifold ultimately yields a better setup overall, Embry notes. “First and second generation S10s come to mind. I designed a set of mid-length headers for these trucks, as well as a set of cast manifolds that are specific to that application. In that situation, I’ll generally recommend that people go with the manifold because it’s such an incredibly tight fit and there’s virtually no room for movement with a header, so you have to get the engine really locked down with poly mounts – or even a solid mount, depending on your horsepower range. The manifold just provides a lot more flexibility in that application.”


He also points out that the Blackheart LS swap exhaust manifolds have proven to be incredibly durable. “We ran these things at 1600 to 1700 degree temperatures for more than a week straight during prototyping, and we couldn’t make them fail. But you can also cut and weld on them, too – we’ve seen a lot of people make custom turbo manifolds out of them.”


One of the places where cast iron manifolds really shine is in turbocharged applications. Their thermal stability and excellent packaging makes them optimal for the high heat and back pressure of turbos.


Still, in situations where exhaust system packaging isn’t as much of a concern, headers often prove to be the better option when performance is the priority. “I think once you start getting north of about 550 horsepower, it’s definitely time to start looking at some 1-and 7/8ths-inch primary long tube headers,” he says. “Otherwise you may be leaving some power on the table.”


Warning: Not all headers are created equal! Headers with thin or poorly machined flanges can cause frequent and annoying exhaust gasket failures. All headers need to have the bolts re-tightened routinely as they are prone to loosening during heat cycles. Another option is a quality locking header fastener.

Many of the same design elements that make manifolds easy to work with from a packaging standpoint also ultimately limit their performance potential. “With the cast manifold being such a compact design, the tube length out of each exhaust port is very short,” Embry points out. “And it’s been proven that to a certain point, the longer the tube length is, the better the performance. On a cast manifold, all of your exhaust ports are dumping straight into the log, whereas with a long tube header, those gases travel all the way down the tube into the collector.”


Embry also points out that Hooker Blackheart LS Swap headers were developed to keep the guesswork to a minimum. “They have the best fit of any header on the market because they’re designed for specific applications with a specific engine mount and crossmember – they’re designed around a package.”


And along with their tight-fitting design, the tubes, flanges, and collectors of these headers are made from 304 stainless steel, so they should last a lifetime, while the attention to detail in their design should make them easier to live with on a day-to-day basis. “One thing we take pride in is ensuring that plug wires have plenty of clearance,” he says. “You won’t run into problems like plug wires getting burnt, or having to buy a special plug wires to run with your headers.”


Available for popular LS swap applications like G-bodies, C10 pickups, multiple F-body generations, along with many other platforms, Embry reiterates that these headers are designed with specific applications in mind from the get-go.


“It goes back to how we develop our swap kits,” he says. “We bring a car in, pull the factory powertrain out, mock up an LS engine in it, and figure out where it’s best suited in the car. From there we prototype engine mounts and a crossmember. Once we figure all of that out, then we build headers, starting with the largest-diameter long tube sets we’re going to offer. When we do that, we’re not thinking about whether or not this set might work in some other car or truck – we’re focused on creating a design which fits that particular vehicle perfectly.”

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