Earlier this year, we began a LS2 testing program at Dan Millen's Livernois Motorsports, one of our favorite Detroit area speed shops. In case you are just tuning in, the LS2 is the amazing, pushrod V-8 that comes standard in many hot GMs, like the base C6 Corvette, GTO, Trail Blazer SS, and Chevrolet SSR. Or, if you've got a project car in your garage that is just calling for one of the most potent all-American small-blocks ever built, the LS2 is available as a crate engine directly from GM Performance Parts. In stock form, the LS2 offers 400 horses and 400 lb-ft of torque from a 10.9:1 compression 6.0 liter displacement. But the LS2 has a ton of hidden potential from very minimal modifications. As an example, Livernois took our LS2 to the dyno, and we demonstrated how easy it is pick up 80-100 hp with a modest camshaft swap and ported stock heads.
To think that a 364-inch small-block that is already making 400 hp can pick up that much power for so little money really points to the advances that GM Powertrain has been making in developing and perfecting the LS family of engines. Part of the secret is the outstanding head design that promotes good low lift velocity and outstanding upper lift flow. With all of that going for it, it makes one wonder just how effective an aftermarket head can be. As we found out in this study, aftermarket heads can certainly add to the bottom line, but it also opens up more questions. Can more inches and a bigger camshaft make an aftermarket head even more valuable? That test will have to wait for another day, but in the mean time, read on and see what some of the best in the aftermarket head business have available for one of America's favorite small block V-8s.
The call went out to several of the top cylinder head manufacturing companies: "GM High-Tech Performance magazine is doing a head shootout on an LS2. Do you want in?" Some shops said no, some never returned our phone calls, but most companies wanted to get in the show. It actually took several months to get this story together. We had the engine and the shop, but a couple of the cylinder heads used in this study are tough to get. For example, the AFR units are extremely popular, and AFR brass had to go above and beyond--pulling a set of their heads from the production line--just to get us a sample. And the TFS LS2 heads tested here are quite clearly prototype units that no one but us had access to outside of the TFS testing labs. In the end, we had assembled four aftermarket heads, and as a courtesy to the shop that was going to be doing all of the labor and testing, we allowed Livernois to throw a set of its very trick, Stage III CNC-ported LS2 heads into the mix. Conflict of interest? No--it simply gives our readership an idea of what a good port shop can do with your stock heads, and then what that head will do for your engine combination. For the engine, we took our stock LS2 and outfitted it with one of the Livernois Stage II camshafts that had worked so well for us before. The Stage II Livernois camshaft specs out like this: 232/232 @ .050, .600 lift on a 114 lobe separation angle. We did this with the assumption that if an enthusiast is to the point where they are shopping for a set of good aftermarket heads, then they probably already have a cam or have their eye on one. The Livernois Stage II cam is a great choice for the serious LS2 street car while in most cases not requiring additional valve clearance, i.e. increasing valve reliefs in the piston face to accommodate the movement of the valves.
On the dyno, we took advantage of a set of Kook's 1.875-inch primary dyno headers. Not only does Kook's offer you the best materials in the business, but their stuff fits. There are a few header shops in the country that we consider to be producing "investment grade" headers, and Kook's is certainly in that club.
All tests were performed on the Livernois Superflow 901 water brake dynamometer, which is good to 2,000 ft-lbs. The Livernois Motorsports dyno cell is temperature controlled, and it was maintained at 68*-70* during each test. Our goal was to keep the air/fuel ratio as consistent as possible from 12.5-12.8 for all tests. Of special note, we did run the AFR head richer and leaner at the request of AFR. We did note some detonation when the engine was leaner, and the power numbers didn't change much either way, so we discarded those numbers. One word on our data interpretation: this is much more of a comparison than a shootout. It's impossible to declare a winner with any of these heads because their applications are endless. However, we are going to attempt to compare these heads so that you are well-informed consumer. After all, this is a great time to be an LS engine enthusiast, and the real winner is the thousands of enthusiasts putting these engines together. With that as background, let's see how the heads stack up.
We started our LS2 head testing with a trip to the Livernois flow bench. Not surprising for the amount of power that the LS2 is capable of generating, all of the heads flowed a lot of air. The AFR and TFS castings offered outstanding low lift flow numbers with solid top end flow, with the TFS head offering the best flow rate test (a super impressive 327 cfm at .600-inch lift.). The completely tricked out stock units were somewhere in the middle with surprisingly close numbers to the two more exotic AFR and TFS heads. And, the Edelbrock and Dart heads, designed for fit on the LS1 block (read: shrouded valves) were slightly lower at the top of the scale while offering impressive low-lift air flow characteristics. Still, any head that flows over 300 cfm and is going on a 364-inch short-block has the potential to make a ton of power.
Air Flow Research (AFR) is a powerhouse in the aftermarket cylinder head business. They offer a wide range of heads that come to the end user with an outstanding reputation for making great power. Their LS1 Mongoose (prepared for this test to run on an LS2 engine) is no exception. The 2.02/1.60-inch intake/exhaust valve arrangement combines with a 205 cc intake port for a delicious combination of high velocity and big flow. Described as "the ultimate street LS1/LS6 aluminum cylinder head," the AFR Mongoose offers a small port that promotes high velocity flow rates for outstanding low lift performance with all of the top end volume that you'd expect in a big-block head. AFR describes its head as "ideal for normally aspirated 346 ci to 396 ci, and it is available with 66 cc and 76 cc combustion chambers. Structural features like Air Flow Research's trademark .75-inch thick head deck, a must for blown and nitrous applications, reinforced rocker stud bosses, and thick wall runners provide unparalleled durability. An exclusive new modern combustion chamber design with double quench pad area helps the LS1 generate huge low and mid lift airflow numbers."On the flow bench, the AFR offered outstanding low lift numbers, especially at .200, .300, and .400 inches of valve lift. Those numbers result in a very torque-rich engine that has a lot of grunt. Of course, with a factory CNC port job, the top end numbers are right there as well--only bested by the TFS head. And, as you'll read, the TFS pieces looked to be custom, hand-ported samples. With the LS2 on the engine dyno and the AFR heads bolted down, our engine cranked out a peak horsepower rating of 547.1 at 6,400 rpm. Stop for a minute and appreciate how much power this is from "just a small-block." At 4,000 rpm, the AFR heads let the LS2 just explode with power, and the torque is right there to move a heavy project vehicle--like a modified Trail Blazer SS.
AFR makes no excuses: they expected to crush the competition. They didn't, but they sure didn't disappoint us. With the aftermarket cylinder head business being so competitive these days, companies are constantly raising the bar. AFR was one of the first companies to offer CNC porting on their own heads in-house, a feature that quickly established AFR as one of the premier head companies in the world. We can easily recommend the AFR head for anyone looking to push their LS2 into some very lofty horsepower territory. The AFR heads will work over a stock head and make most other castings look silly. And, we have a sneaking suspicion that the AFR heads will only get better the harder you ask them to perform, big-inch or power-adder style.
The Dart heads are a bit of a mystery to us. They appear to be very basic, as-cast aluminum heads for an LS1 engine. That, you would think, would hold them back severely, which in fact it did, but not as badly as you would imagine. The Darts offer a small combustion chamber, 2.02/1.60-inch valves and a huge 225cc intake runner. That sounds like an odd combination when compared to the other heads, but the Darts are clearly designed with a head porter in mind. Sure, you can bolt them right on like we did, but their true beauty is in what can come from a trip through the port shop.
On the flow bench, low-lift flow numbers were quite a bit lower than the factory-ported pieces. In fact, the Dart head trails those tested here, clearly indicating that this is a LS1 head in an LS2 comparison. But, what happens with you open up that LS1 chamber, port the runners, and start blending the combustion chamber? You'll have to wait for another day for us to find the answer to those questions.
On the engine dyno, the Dart heads stayed right with the other competitors--that is, until they reached 5,500 rpm and the torque went away. Still, a little port work could easily solve that. The horsepower is right there, flat and broad from 4,500 rpm until past the engine's peak at 6,700 rpm. The Dart heads have a lot of potential, and this study only hints at what they offer the end user. All things considered, a Dart-headed LS2 would be hard to distinguish from the other castings.
Dart heads have always been known as affordable, feature-rich heads, and these LS1 versions continue that tradition. The Dart heads will likely really wake up big time with some attention from a capable head porter. If we do pull off a stroker test or better yet, a stroked/cam/nitrous test, the Dart heads could very well win the thing. As we said, the Dart heads are a bit of a mystery to us.
Edelbrock is a huge company that has developed an exemplary reputation for offering great products at a competitive price. Not exclusive to Edelbrock, but you have to appreciate it when something comes out of the box, fits right, and bolts on. That peace of mind is enough to sell parts regardless of if they work. But Edelbrock heads work, and these Edelbrock/Lingenfelter LS1 CNC-ported lovelies are no exception. Designed as a direct bolt-on for an LS1 engine, these heads offer a 65cc compression ratio to retain the stock compression ratio, 2.02/1.57-inch valve sizing, and a 202cc intake runner.
Like the Dart head, the Edelbrock/Lingenfelter LS1 was working with a disadvantage having been designed for an LS1 engine. In case you are just getting into the LS game, one of differences that you see in these two engines is that the bore of an LS1 measures 3.90 inches compared to 4.00 inches for the LS2. Of course, this helps explain the cubic inch difference, but it also unshrouds the valves, meaning that the heads can flow better because the valves aren't closed in by block material. A big bore is the way to go to help maximize head flow, and the LS2 has this built right in. With an LS1-specific head, the combustion chamber still carries that limitation; so LS2-specific heads should always perform better.
Or, so we thought. On the flow bench, the Edelbrock heads stack up surprisingly well. Our source at Edelbrock knew that he was sending a "knife to a gun fight," but these numbers offer promise if/when Edelbrock ever cuts loose with an LS2-spec head.
Where does the Edelbrock head fit in? Blower cars. All of that weight buys strength. And, with a blower trying to push the head off the block, the Edelbrocks seem to be the answer to keep the combustion chamber intact. We also have to remind you that these are the LS1 castings, and that an LS2 version is in the works. With an excellent inherent design and a very capable research laboratory, look for an LS2 Edelbrock head to really offer the goods. If you've got a street car, and you want a very solid aftermarket head, this would also make a good choice. But, we envision these big boys sitting under the hood next to a Vortech or ProCharger.
As the name indicates, Livernois Motorsports throws the book at their Stage III LS2 cylinder head. Starting with a new set of LS2 heads, they run them through a five-axis CNC machine for port work that mimics their in-house hand port work. Fully assembled with Manley valves and Manley titanium retainers, this is a great example of what a good port job can do for an already outstanding factory head. With the better springs, these heads will work to .670-inches of lift, so you can put a very aggressive camshaft into the mix before you start to run out of valvespring.
On the flow bench, the Livernois LS2 head kept right up with the out-of-the-box aftermarket units, flowing in excess of 320 cfm at .600-inch lift. And that doesn't come at the expense of good low lift flow, so the torque and good street manners are still there.
On the engine, these heads are just as impressive. Running up to and over 540 hp, they help the LS2 exhibit a nice linear horsepower curve. Torque seems to start to suffer at 5,000-5,500 rpm, but that's right where the horsepower is in the power band.
Where these heads would shine is on a street racer's car that requires the stock look without giving away the obvious modification of an aftermarket logo on the end of the head. With this kind of performance from a stocker, you get a real good idea of just how amazing the stock LS2 head is to begin with. Unless you are building big inches or adding nitrous or forced induction, you may want to go through a couple of generations of modifications with your stock LS2 head at a good head shop before you fork over the big money for the aftermarket unit. On the other hand, if you are looking at making over 600 horses, go with one of the larger aftermarket pieces from the get go and don't look back.
Wow! What a cylinder head. With a reputation for absolute excellence in flow design, it seems the engineers at TFS have finally turned their attention to the LS1, and for the first time in these heads, the LS2. We waited and waited, and finally these heads showed up. They were worth the wait. Are these good examples of what you'll get when you open the box on your own set of LS2 heads by TFS? We really don't know because it would appear that we got ourselves a hand-finished set of heads just for this comparison. These were clearly the most "worked" heads in the group. Mirror polishing, perfect ports, and a very racy look told us that these things were serious. Regardless of their status in the TFS catalog, TFS did a great job with these LS2 heads.
As they did when they revolutionized the Ford small-block market, TFS looked at the LS1 cylinder head with an open mind. From their Web site, we learned that "during the development stage, Trick Flow engineers determined that the valve angles needed to change from 15 to 13.5 degrees. This change decreased valve shrouding, increased mid-lift airflow, and increased rocker arm-to-valve cover rail clearance. Testing also proved that relocating the spark plug position in the combustion chamber further enhanced mid-lift airflow and increased the rigidity of the casting to prevent cracking in the chamber area. Furthermore, additional material was added to the rocker arm mounting points for high-rpm valvetrain stability."
On the flow bench, the TFS units flowed over 327 cfm at .600-inch lift--a real number for the cam we were using in this study. They also offered up solid low-lift numbers that bested--or at the very least kept pace--with the other heads in this study.
On the engine dyno, the TFS heads recorded the highest measured horsepower and torque. Again, we want to remind our readers that this isn't the point of this test, especially given the detailed heads (let's call them what they are: prototype LS2 heads) from TFS. And, looking at the dyno graph, the LS2 outfitted with these heads shows a nice horsepower curve that gets to a peak number and just stays there.
If you are serious about making power with your LS2, you have to look at the TFS. We like the fact that, like the AFR, you can get them with a CNC port from the factory, and if TFS is going to offer the hand finishing that we got on our test heads, it's a bargain. Big inches, monster cams, blowers, nitrous--bring them all on. We can't wait to see where these heads take us in the future.
After the engine dyno stopped screaming, we were blessed with the fact that it's a great time to be into LS engines. Not only do the stock heads that come on an LS2 hold a ton of potential, but also big manufacturing companies are really putting out some great products. As for recommendation of a head for your engine project--that's something that is on a case-by-case basis. But, we can say that there certainly is a head out there for whatever you are building. If you are on a budget, the stock head rocks with a little attention. In fact, as we showed with our first test on the LS2, a nicely done set of stock heads with a modest cam is probably all that the typical enthusiast needs. If you want more, then step into the AFR, Dart, Edelbrock, or TFS offering. They each have their own unique strengths with none of them offering false advertising. With the performance starting to even out, it seems that we may have to push this collection of heads a little harder. How would they stack up on a 404-inch LS2 with more cam and compression? Or, what if we introduce a 150-horse shot of nitrous into the picture? And, finally, which head performs better when you put 8-12 psi of supercharger boost into them? These are just some of the questions that we hope to investigate in future LS2 testing.
However, next time around we'll be looking at the killer new L92 heads and L76 intake that GM Performance Parts has coming out for the LS family of engines. Stay tuned LS lovers, we've got a lot of cool stuff coming your way.