The LS1 Enforcer Cylinder Heads From AFR

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The LS1 Enforcer Cylinder Heads From AFR


Developing aftermarket cylinder heads requires technical knowledge and a keen understanding of what customers want, and in possessing and displaying both traits, Air Flow Research (AFR) developed its relatively new Enforcer series of heads. Today, we’re going to look at the AFR LS1 Enforcer heads specifications, some background on their development, and we’ll show you what you really want to know: how they perform on the dyno.

There was a lot of buzz around the Enforcer cylinder head series when AFR announced it in 2019. The company has established itself as one of the best when it comes to creating quality CNC heads, so the expectation for an as-cast cylinder head was high. AFR made it clear from the start these weren’t just going to be some cheap junkyard heads — they would come from the factory with high-quality parts already installed as an option.

Breaking Down The Enforcer

To make sure the Enforcer heads would have a solid foundation, AFR used its Permanent Mold “As-Cast” Technology surfaces via A356 aluminum as the material. This means the major areas of the cylinder heads, like the intake runners, exhaust runners, and combustion chambers would have the most accurate and repeatable port location, along with a higher level of performance.

When you dissect the Enforcer heads it quickly becomes obvious that AFR wasn’t playing around with the parts it chose to offer on the fully-dressed units. After you pull a set of assembled Enforcer heads out of the box the first you’ll notice is just how well they’re made. The heads we received for our test came with the standard PAC racing springs, viton valve seals, machined bead valve locks, hardened spring seats, ARP rocker studs, and AFR’s adjustable guideplates. The heads also came with a full set of one-piece 8mm 21-4N stainless steel valves.

The Enforcer heads come assembled from AFR with top-notch hardware.

Overall, the specs of the Enforcer heads are exactly what you would expect from a budget cylinder head. The Enforcer heads have a 210cc intake port volume along with an 82cc exhaust port volume. The heads use a standard LS 15-degree valve angle with a 1.500-inch outside diameter valve spring pocket. The combustion chamber measures 64cc’s in size and the heads need an engine with a minimum 3.900-inch bore diameter.

Why AFR Introduced The Enforcer

There’s no doubt that AFR has an established reputation as a company that provides high-quality, CNC-machined cylinder heads for different applications. The Mongoose line of LS heads has been helping enthusiasts make loads of horsepower for some time, but not everybody has the kind of money it takes to buy those cylinder heads.

AFR’s Tim Torrecarion sheds some light on the subject of how the Enforcer heads found their way into development.

“The Enforcer line of cylinder heads was created because we noticed there was a gap in the marketplace where customers wanted the AFR head, but didn’t have the budget at the time for a set of CNC heads. These customers were either new to modifying cars, or building an engine on a budget but still wanted new heads. The Enforcer line gives them a quality product at an affordable price, and that was the main reason for coming out with these cylinder heads.”

There’s no cleaning needed when you purchase these heads, you can bolt them on and hit the road right away.

Knowing that customers wanted a cylinder head that flowed better than a stock LS1 casting, AFR went to work on creating the Enforcer. Since this was going to be a budget-friendly part from the start, AFR wouldn’t be able to put the same port on the heads as its CNC line of heads. This is the reason why the Enforcer’s don’t boast the same impressive flow or horsepower numbers of the Mongoose line.

AFR took some inspiration for the basic framework from a set of GM castings that saw a limited production run when the LS1 first came out.

“These heads are pretty close to the GM 243 castings. We used that as the base because we looked at your average budget LS engines people were building and saw they would be using a 6.0-liter or smaller engine to start with — usually it’s a truck engine. The customers were looking for higher compression from the heads, so using a 243 cylinder head worked. This is why the Enforcer cylinder head uses the 64cc chamber versus the larger factory chambers that added compression to bump up the horsepower,” Torrecarion explains.

Finding a set of stock 243 heads used can be a time-consuming task, and if you find a set they’re going to need some work. They’ll need to be cleaned up, possibly require some machine work, and have new valvetrain parts installed that will work with a high-performance application. That’s what makes the Enforcer heads so attractive: they save you the time of looking for something used that was never produced in a large volume from the factory.

The Enforcer line of cylinder heads were created because we noticed there was a gap in the marketplace where customers wanted the AFR head but didn’t have the budget at the time for a set of CNC heads. – Tim Torrecarion, AFR

Why Should You Swap Replace Stock LS1 Heads?

The typical modification path for your average LS engine eventually leads to a different set of cylinder heads for the enthusiast that’s looking to go beyond bolt-on horsepower. When you start researching LS1 heads it can get pretty confusing, especially if you don’t see yourself building a full-on race car.

According to Torrecarion, the Enforcer heads are perfect for those who want more power over a stock LS1 cylinder head and need to stay on a budget.

“In a street application that’s naturally-aspirated, you’re going to see some quality horsepower gains by going to a better set of cylinder heads. The Enforcer heads will unlock the flow potential of the LS engine at a budget price point. A lot of customers buying second-hand truck engines are looking for something that will improve performance and reliability versus a full-on racing head. That’s where the Enforcer cylinder heads come in…they’re better than stock and work well with other modifications.”

These heads are an outstanding choice for someone who’s building a nice naturally-aspirated engine on a budget that wants some upgraded heads. They can also work on an engine with a power-adder, however, they aren’t meant to deal with elevated amounts of boost or cylinder pressure.

“These heads are targeted for those who are doing a budget swap with a truck engine that wants some additional horsepower. You can unbox these, put them on a car, and use them as long as they fit the engine’s bore size. Typically, there’s no piston-to-valve clearance issues, however, it needs to be checked just in case. A shop doesn’t have to spend the time cleaning up the heads or any extra work so that saves you money on the final bill,” Torrecarion says.

Get Into The Flo

A set of stock GM 241 heads will only flow 227/180cc at .600, so the Enforcer heads are a nice step up from that. Here are the flow numbers for the Enforcer heads from AFR’s website. As you can see, these heads deliver great flow numbers for the price.

210cc Street Head Flow Chart
.200 .300 .400 .500 .550 .600
Int 148 209 253 265 268 268
Exh 105 150 180 199 204 207

Test conducted at 28-inches of water (pressure) on Superflow 600
Bore Size: 4.060-inches, 3/4-inch radius plate exhaust, 1-3/4-inch curved pipe

Now, to really get the most out of swapping heads on an LS1 you’ll want to make sure all other supporting modifications have been done, as well. Usually, this means the fuel system will need to be addressed along with a healthy camshaft, an aftermarket intake, and a tune. All of these things will work with an upgraded set of heads to create more horsepower.

“There’s a lot of tweaking that can be done with a tune to improve performance along with a set of heads like the Enforcer. The OEM camshafts are designed for more daily driving and won’t have enough duration and lift to match the cylinder head’s sweet spot. If your camshaft doesn’t have enough lift it’s not going to let enough airflow through the heads so you won’t see the power levels you expect. These heads are a great way to add power to a truck engine without killing your bank account,” Torrecarion says.

Installation And Dyno Results

Chances are if you’re looking at using a set of AFR Enforcer’s it might be your first time swapping heads on an LS1. At first glance this project might seem fairly complex, however, it really isn’t that bad and just comes down to knowing what needs to be done before you begin. There are plenty of how-to videos out there on the actual process of swapping LS1 cylinder heads, so with a little bit of research, you can get a pretty solid education before you begin.

To get some good real-world numbers on the capability of the Enforcer heads, we took a set up to our friends at Big 3 Racing in Hinkley, Ohio. Chuck Stefanski is one of the owners at Big 3 and knows a thing or two about how to make an LS1 fast. Over the years, Stefanski has done countless LS1 head swaps and he shared some of his knowledge with us about what to know before you turn a wrench.

Swapping an upgraded set of heads onto your LS1 is a great way to pick up solid horsepower.

“Swapping the heads starts with being prepared by making sure you have all the parts and tools needed. It’s also a great time to swap a cam, add headers, upgrade the intake manifold, and go through the valvetrain if needed. If you already have these mods then the swap is pretty straightforward.”

Big 3’s tech, John Elam, needed to collect supplies to get the job done. A set of OEM LS9 head gaskets, FelPro fasteners, FelPro valley cover gaskets, and NGK tr55 spark plugs were used to complete the swap. Stefanski also noted they used OEM MLS exhaust gaskets and lifters as part of the swap.

The Enforcer cylinder heads are a direct fit and don’t require anything special to add to your LS-based engine.

“You will also need to make sure you have all of the torque specs as well as the torque sequence for the fasteners during the swap. Be careful when unboxing the heads so you don’t mar the deck surface; the same goes for the deck surface of the block. Now, if you’re installing new lifters, soak them overnight in a container of good oil. Be sure that the dowels stay in the block so you can align the new head when installing it. It helps to chase the threads of the cylinder heads to clean everything out. You also shouldn’t use any abrasives on the deck surface. These are just some of the basics,” Stefanski explains.

These heads would be great for anyone that is looking to change heads or for someone that is doing a new engine and needs a set of heads to top their short block. – Chuck Stefanski, Big 3 Racing

Before we put the new Enforcer heads on the GTO testbed, it had already been modified with a Brian Tooley Racing Stage 3 camshaft, LS2 intake, 90mm throttle body, Stainless Works headers and exhaust, high-flow catalytic converters, and a K&N cold air intake. When Stefanski made the initial dyno pulls with these parts the GTO put down a respectable 396 HP and 346 ft-lb of torque. After the heads were swapped out, the GTO laid down 418 HP and 357 ft-lb of torque.

“Picking up 22 horsepower to the tires is no easy feat for a naturally-aspirated application,” Stefanski says. “We normally see around 15 HP increase with unported 243 heads in this application. The car pulls way harder now, and I was able to increase the timing by one degree and not receive any knock retard while picking up the power with these heads. The engine pulls past 6500 rpm now, where before with stock 241 heads it leveled off around 6300.”

You can see the gains the Enforcer heads provide over the stock LS1 castings. These heads made more power at every RPM level over the stock heads.

The dyno results are typical of what you would see for a vehicle that has these kinds of modifications, according to Torrecarion. There are a few reasons why the Enforcer heads are able to pick up these numbers over the stock LS1 castings.

“What you’re seeing here is the CFM number at work in a real-world setting,” Torrecarion explains. “The big focus is to look at more than just the peak flow numbers, but what the heads can do in the mid-range, and the dyno numbers show where these heads are an improvement over the stock units. A big advantage they provide is an increase in compression. If the stock heads have a 70-72cc sized combustion chamber, dropping that to 64cc’s is what bumps up that compression and in turn increases the horsepower.”

The AFR LS1 Enforcer cylinder heads are the perfect way for someone to get a quality product from one of the best in the business. When you look at the dyno numbers you can clearly see they provide plenty of performance at a great price. If you’re thinking about swapping heads on an LS-based engine and are on a budget you need to check out the Enforcer cylinder heads.



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