The largest growing portion of the small-block Chevy head market has to be the 200-cc and larger intake port volume segment. These heads are not only great for larger displacement engines, but also for smaller engines looking to make power at higher engine speeds. With a rather small area to work with on a small-block, port volumes for standard 23-degree heads range all the way up to 230-cc.
This category of heads is intended for small-blocks larger than 400-ci or engines that are designed to run at engine speeds up to or more than 7,000 rpm. Larger intake ports need either a larger engine or more RPM to create the velocity necessary to make power.
Especially with the larger intake port heads, some manufacturers raise the exhaust port in search of more exhaust flow to match the larger intakes. Be aware of this because a taller exhaust port creates header-tochassis fitment problems.
Of course, intake port volume is just a convenient starting point from which to categorize these heads. What we really want to look at is each cylinder head’s port flow numbers combined with their port crosssectional area. Evaluating each of these individual sets of numbers give us some insight into how each of these heads would respond on a given engine.
Clearly, there are a ton of variables that can affect overall engine performance. Hopefully by this point in the book, you have deduced that the biggest intake port with the highest peak valve lift flow numbers may not be the best choice for a particular application. Instead, we must take into account how the engine will be used and pay attention to the vehicle in which the engine will be used. Ideally, we want to strike a combination between the short-block, the heads, and the induction system. This helps make outstanding torque, and gives a wide power band between peak torque and peak horsepower that contributes to moving the car down the drag strip or around corners at a road course that will thrill and amaze you.
This chapter also encompasses the widest selection of intake port volumes, so it might be worthwhile to look at displacement in relation to these heads. The smaller the displacement, the less “demand” each cylinder makes on a given port. This can be related directly to velocity since crosssectional area determines the speed at which the port can deliver the air to the cylinder. Therefore, a larger cylinder (more displacement) places a greater demand on the intake port, achieving maximum port velocity sooner for a given cross-sectional areas. We would want to feed that larger cylinder with a larger intake port. Basically, we can condense this down to a statement as simple as: A larger-displacement engine can handle a larger intake port volume.
Especially with the larger intake port heads, some manufacturers raise the exhaust port in search of more exhaust flow to match the larger intakes. Be aware of this because a taller exhaust port creates header-tochassis fitment problems.
Since velocity plays such a crucial part is this evaluation, it also deserves attention. Consider that a larger port cross-sectional area could be used successfully on a smaller-displacement engine as long as the goal is power at a higher RPM. This would demand a longer-duration camshaft. We get into that in Chapter 12, but the basics behind this is that a longer duration cam adds “time” in degrees to allow the port to fill the cylinder at much higher engine speeds. A larger port cross-sectional area works with this higher engine speed to achieve its maximum port velocity, enhancing peak horsepower. Another way to look at this is that the longer duration camshaft simply moves the torque peak to a higher engine speed. This is assuming that everything else functions normally, the rods don’t decide to ventilate the oil pan, and the valvetrain doesn’t try to eat itself. Besides requiring a high quality short-block, the heads also must be equipped with some good valvesprings to be able to withstand the rigors of high RPM use.
This means that you can place a larger intake port volume head on a smaller-displacement engine and make it work by spinning the snot out of it to achieve the horsepower goal. This, for example, is the basics behind how naturally aspirated drag race engines are constructed—they just spin ‘em faster. Of course, this automatically kills low-end torque and really hampers low-speed driveability since the engine loses much of its low RPM torque through lost volumetric efficiency, a very lateclosing intake valve, and tons of overlap. Getting back to a specific usage, this also requires a high-stall speed converter (or a manual trans), lots of rear gear, a good suspension, and all the rest that goes with a high RPM package.
Angle milling is a common practice when attempting to reduce the chamber volume. This also has a small affect on the overall valve angle. Keep in mind that this also changes the relationship between the head and the intake manifold sealing surface that must also be rectified.
The Edelbrock E-Tec is the Fun Team’s 200-cc big-cousin version of the original GM Vortec iron head. This head offers outstanding velocity numbers, which promises great torque in a 355 or 383-ci small-block.
Many head companies warn not to deepen spring pockets when modifying heads. This is mainly because the area between the top of the bowl area and the bottom of the spring seat is often very thin. Sinking the spring pockets to fit a larger valvespring can cause serious problems that you should strive to avoid.
While those high RPM motors are romantic, for the street they are for the most part impractical and not very durable—especially those stiff valvesprings. The more attractive alternative for a hot street engine is to trade RPM for displacement. Instead of a high-winding 355 or 377, let’s look at the advantage of a larger cubic inch engine along the order of a 420 or 434-ci bruiser. A small-block of this size can easily take advantage of a 215, 220, or even a 230-cc intake port to create excellent port energy with the combination of good airflow and a reasonable intake port cross-section.
Another point worth emphasizing again is to not ignore the exhaust side of these cylinder heads. It’s all too easy to get lost in the evaluation of intake ports and overlook the requirements of the exhaust side. If the cylinder can’t push all the bad air out, there won’t be as much room for the good air on the next cycle. It’s as simple as that. As mentioned in Chapter 3, there is considerable evidence to support enhancing low-lift exhaust port flow to improve cylinder blow-down when the cylinder pressure is the highest. There’s also the data from both Duntov and Smokey Yunick that emphasize work in the area of 75 percent of peak valve lift on the exhaust side. So, for a 0.550-inch peak valve lift figure, this means that emphasizing exhaust flow around the 0.410-inch valve lift would be beneficial. These two approaches may appear to be contradicting, but the truth is that enhancing flow at every valve lift point will certainly improve cylinder scavenging.
This is not supposed to be a theory chapter, but it is important to have an idea of how best to apply the different cylinder heads that are offered within this category. Now we take a look at each of these heads a little more closely.
Edelbrock E-Tec 200
This is the larger cousin of the Edelbrock E-Tec 170 and interestingly falls right in the middle between the smaller Edelbrock Performer RPM and the Victor Jr. 23-degree heads. Edelbrock’s street cylinder head philosophy has always been to deliver excellent velocity along with decent flow numbers to create strong torque and horsepower for a solid street engine. While the E-Tec’s mid-lift intake flow numbers compare favorably to many of the 200 to 215 heads in this category, if we look back at the flow numbers for heads slightly smaller than the E-Tec, there are several smaller heads that out-perform the E-Tec at this level.
However, the Edelbrock head does do well up around 0.500-inch lift with a 253-cfm flow number. Combined with a relatively small cross-sectional number, the E-Tec offers excellent port velocity numbers due to its smaller port cross-section and intake valve, which maintains the energy up through its lift curve. Curiously, the stronger flow velocity numbers are at the top of the curve, with the lowest velocity at 0.300-inch lift. If you buy the concept that 65 percent of maximum valve lift is one area where we concentrate our effort, it would appear this head could use some work in the 0.300-inch lift area, even if we have to sacrifice some flow at the top of the curve. From this standpoint, it appears that a minor amount of pocket porting or valve angle enhancements on the E-Tec in the mid-lift flow area could make this head work very well. On the exhaust side, Edelbrock does not back-cut its valves, which is an incredibly easy thing to do to these heads to enhance the exhaust port efficiency. With those couple of changes, the E-Tec is a real player for a mild street engine that enhances the torque on a midsized small-block like a 383-ci.
Dart Iron Eagle 200
This is Dart’s iron entry in the 200-cc port size market. The flow numbers are respectable, but not outstanding. We won’t spend a lot of time on this head since Dart no longer sells it, having replaced it with the Platinum series of iron castings—a far superior head. The flow velocity numbers are acceptable since they come in around 100 cfm/sq.in., but frankly there are several other heads in this same port volume category that offer greater flow rates and velocities.
The Dart Iron Eagle 200 is one of Dart’s earlier castings that exhibits decent flow potential and respectable low-lift velocity numbers.
Dart Platinum 200
As mentioned, the Platinum series has replaced the original Iron Eagles, with an emphasis on Dart’s wet flow technology. This focus on the intake side is not necessarily reflected in dry flow-bench testing. This is because the focus with the wet flow technique is to modify the intake port, improving the fuel flow pattern as it exits past the intake valve and into the cylinder. Nevertheless, the Platinum 200 is still an excellent cylinder in terms of intake flow with 250 cfm at 0.500- inch lift. There are other 200-cc heads that flow more in the mid-range, but these heads also rely on much larger port cross-sectional areas. The 200-cc Platinum employs a mere 2.06 sq.in. minimum port cross-sectional area, which is among the smallest of all the 200-cc heads and of this entire category. It’s also smaller than the first version AFR 180 and AFR 195 heads. This equates to top five status (within the 200 to 230-cc port volume category) in terms of flow velocity at the higher valve lift numbers.
The Platinum 200 also delivers excellent exhaust flow with average mid-80 percent E/I numbers in the low- to mid-lift range where exhaust flow is especially important. All the new Dart Platinum and Pro 1 heads come equipped with 30-degree backcut valves as standard equipment on assembled heads, which is one reason for their performance. The cast-iron Platinum heads are excellent castings, with a very nice finish both inside and out. As iron heads go, these are some of the nicest castings we’ve ever worked with. There is also potential for improvement since there is no additional handwork done to the bowls on either the intake or exhaust sides. While not as rough as production heads, we found a few sharp edges on most of the transitions between the bowl and the deepest throat angle. Be very cautious here since sharp edges are also acknowledged as beneficial to shearing fuel and creating fuel atomization. We recommend making changes only if you have access to a flow bench to evaluate your changes.
Dart Pro 1 200 Aluminum
This is Dart’s aluminum version of the iron 200. As you can see from the flow test numbers, this head is similar to the Platinum. In terms of development, this head came after the Iron Eagle, but before the Platinum head. As this book was completed, Dart converted all its Pro 1 heads to Platinum status with wet flow technology, although because of deadlines we did not have access to these heads for testing. This means that, while the Pro 1 is a great head, the newer wet-flow Platinum versions should offer comparable flow and performance to the iron Platinum versions. In fact, an early test of these Pro 1 Platinums indicated that the aluminum heads, with their minor blending of the seat into the throat, were worth as much as 20 hp over the iron Platinum versions. Also keep in mind that all the Pro 1 tests in this book are on as-cast intake and exhaust ports. Only the 227 Dart head is fully CNC ported.
This is the main reason why the Platinum head of the same port volume appears to be measurably better than the aluminum Pro 1. The last head to hit the market generally has an advantage. The exhaust flow is very similar to the Platinum 200 and it appears that the two exhaust ports are probably the same. With a decent low-80 percentile E/I, the Pro 1 offers respectable exhaust flow, which may even be good enough to warrant a single pattern instead of a dual-pattern cam when it comes time to select a camshaft. Another worthwhile factoid concerning all the aluminum Dart heads is their excellent pricing. These heads are not the cheapest on the market, but they do represent an excellent performance per-dollar investment.
The Pro 1 Dart heads like this aluminum 200 are a step up from the Iron Eagle line both in flow and less weight.
World Products Sportsman II
This is one of the original smallblock Chevy aftermarket iron cylinder heads. Considering that this is a longin-the-tooth head, it is still a viable casting with potential. Right off the bat, it offers respectable flow numbers, especially compared to much newer heads in the same category such as the Dart Iron Eagle 200 and the Brodix Race-Rite 200. The intake port velocity numbers are actually better than we anticipated given its 2.19 sq.in. port cross-section. Numbers in the 110 cfm/sq.in. area at the higher valve lifts are actually respectable, although like many heads in this category, the lowest port velocity occurs at 0.300 inch of valve lift, right where a head with a valve lift of 0.500 inch really needs to shine. Like the E-Tec head, this is an area where you could modify the throat area or perhaps fool with valve angles and back-cuts to increase port flow in this mid-lift area without sacrificing too much flow or velocity in the higher areas. The intake velocity curve was one of the surprises after calculating the velocities for all the heads in this category. We expected the Sportsman II to be one of the under achievers, but were pleasantly surprised by its velocity numbers.
The World Products Sportsman II iron head is the oldest of the aftermarket heads and has become outclassed by this latest surge of new 200-cc and larger small-block heads.
On the exhaust side, the Sportsman II starts out strong with an 80 to 75 percent E/I, but this quickly drops off to the high 60 percent range, which indicates that this head is certainly exhaust limited in terms of horsepower. This is probably due to port area restriction, but again, don’t overlook simple tricks like a 30-degree back cut on the exhaust valve and some bowl work to increase port flow at the higher valve lifts. Out of the box, this head is not stellar, but with some simple modifications it can still be a player in the small-block market, mainly due to its potential.
Brodix Race-Rite 200
This is the second head along with the Race-Rite 180 recently introduced by Brodix. The RR 200 offers a relatively large 2.18 sq.in. cross-sectional intake port area, which tends to hurt the velocity curve, especially compared to other heads in this area with much smaller cross-sections. The intake flow curve isn’t real strong, and that is combined with a slow velocity curve that only begins to shine at the very top of the lift curve at 0.600 inch. Here, this head offers decent flow and velocity, but frankly we don’t think there are too many engine builders willing to put a 0.600- inch lift cam in a small-block with only a 200-cc intake port. Adjusting this flow curve to improve the 0.300 and 0.400-inch lift numbers would also pump up the velocity, which could prove to make this head a respectable performer.
The Brodix Race-Rite is the Arkansas-based company’s effort at a revised 200-cc intake port head for the street. The smaller port volume is intended for 383 to 400-ci street small-blocks with a decent cam.
The exhaust side is not much better since there are several heads in this category that offer substantially stronger exhaust ports. This leaves the Race-Rite 200 in a bit of a quandary since its high-lift intake port flow numbers can only be questionably supported by the exhaust side since it begins to lay down compared to the intake port’s performance. This means the head needs a substantially longer exhaust duration in order to compensate for the exhaust port’s performance. Again, there are ways to enhance this head’s performance with back-cutting the exhaust valve and pocket porting that would certainly enhance its performance. But when there are several heads on the market that out-perform it right out of the box, the Brodix RR 200 has its work cut out for it.
AFR 210 Version 1
Evaluating the flow and velocity numbers on this head really makes it difficult to look past it to any other head for sheer performance. Before we get started, notice that this head is referenced as Version 1. That’s because as this book is written, AFR has just completed work on a revised Eliminator version. It’s also important to note that the test on this head represents the full CNC Competition porting effort available from AFR, while most of the heads in this category are as cast. This also makes this AFR 210 head more expensive than most, but you get what you pay for.
First of all, the entire intake flow curve is exceptionally strong. Looking just at intake flow at 0.400 inch of valve lift, the relatively small AFR 210 outperforms most of the heads in this chapter, even ones much larger in port volume and area. The minimum port-cross-section for this head is a relatively compact 2.07 sq.in. By now you should be able to tell that combined with excellent flow numbers, this means outstanding velocity numbers. The 210’s minimum velocity number is 100 cfm/sq.in., while the higher valve lift numbers only get better with a peak of 130-plus cfm. If you remember from Chapter 3, an excellent intake port velocity number for any cylinder head is in the neighborhood of 130 cfm/sq.in. The only thing that would make this head better would be higher velocity numbers at the 0.300-inch lift point.
The original AFR 210 head combines the awesome power of excellent flow numbers with a relatively conservative port cross-section to deliver tremendous velocity numbers that promises excellent torque and horsepower.
On the exhaust side, the AFR 210 delivers excellent low-lift flow numbers, especially at 0.100 inch of valve lift where it actually exceeds the intake side flow number with a smaller valve. You can guess what that does for exhaust flow velocity. It’s possible this head would perform well with a minor amount of additional exhaust event duration, but not much. Overall, with its excellent port velocity and flow numbers, this first version AFR 210 head is tough to beat compared to the other heads in this category.
AFR 210 Eliminator
Before we get into the details, the AFR 210 Eliminator was not released until after this book was sent to the printer, so we had to go with AFR’s prototype flow numbers. This is not something we’re comfortable with since the production ports tend to be not quite as good, but AFR has consistently delivered on 95 percent of the promise, so we went with their numbers.
As strong as the original AFR 210 was, the latest version combines improved flow numbers with a slightly smaller cross-section for even more torque potential. That means more power under the curve.
Our initial look at the 210 came at the prototype stage just as head specialist Tony Mamo completed the final tweaks on the port. Again, AirFlow Research offers this head in the competition mode as a full CNCported configuration. Obviously, this offers the most flow potential along with the highest cost. There is also a street configuration as well that compromises the flow a bit, but it is somewhat less expensive. The port cross-sectional area for this head is substantially larger than its predecessor at 2.30 sq.in., but when the flow numbers deliver 308 cfm at 0.600- inch lift, that places the velocity number at 134 cfm/sq.in., which puts this casting at the head of the class.
A close investigation of the Eliminator’s intake pocket reveals an increasingly common flow director vane. Interestingly, AFR’s version directs the flow in an opposite direction compared to the similar vanes found in the Dart Platinum series heads. While Dart’s vanes are dictated by wet flow techniques, AFR has relied instead on the dry flow bench and a wide bowl wall to induce a circular motion to the exiting air and fuel, but in a direction away from the exhaust valve. The mid-lift numbers are also just short of phenomenal in that they also place the velocity curves solidly in the 120-plus range. These are the kind of numbers that push the torque curve up and make a properly cammed engine a strong accelerating engine.
The exhaust ports have also received their share of attention, starting with a 0.250-inch raised centerline, which will no doubt cause a few issues with header fitment. But this is a reasonable price to pay for flow numbers that reinforce why the port is where it is.
Dart Iron Eagle 215
The Dart Iron Eagle 215 head could probably be best described as a mid-pack player. We’ve included it here even though Dart actually doesn’t sell this head any longer. It has now been replaced by the Platinum series of iron heads that all benefit from Dart’s growing experience with wet flow technology. We’ve included the Iron Eagle in this category mainly because they will be around as used heads in the market for quite some time. The Iron Eagle’s intake port flow numbers are respectable, but the port velocity numbers are not impressive and begin to fall right from the 0.100- inch valve lift starting point. The exhaust side does a good job of supporting the intake with decent percentages of flow, but keep in mind that with somewhat weak intake flow numbers, the percentages immediately look better. When comparing the exhaust flow to other heads in this category on a pure flow basis, again the Dart Iron Eagle 215 is mid-pack. Our recommendation is that these are decent heads if you find them for a good price, but the Platinum series heads are a better choice if you are going to go with an iron head.
Dart Platinum 215 Iron
In the shuffle of multiple cylinder heads, especially within this category, it’s easy to overlook the “middle child” heads because the big guys seem to get all the press. But in the midst of our testing, we ran across some good dry flow numbers for the Dart Platinum 215 head that combine with a decent small port cross-section of 2.15 sq.in. Plus, with the promise of Dart’s expertise in wet flow, this head may be the sleeper in this whole category. The Platinum offers very good velocity and flow numbers on the intake side along with an equally good price if you’re willing to add the extra weight of the iron castings. With 253 cfm at 0.500-inch lift combined with a 117 cfm/sq.in. velocity component, this head shapes up to promise excellent torque.
The combustion chamber is a critical part of the entire cylinder head equation, yet it is difficult to evaluate. This is the chamber on the Dart Iron Platinum 215 head. Note how the spark plug is very close to the exhaust valve.
The best way to identify a Dart Platinum intake port (either aluminum or iron) is this vane that is becoming increasingly popular as a way to help direct fuel past the intake valve in a wider, more diffused pattern. This improves combustion efficiency and power. The Platinum also employs a much narrower valvestem boss, which improves flow.
When we get into the larger Dart 215 heads, the company’s true abilities begin to come into play. The Dart Pro 1 215 Platinum is an excellent choice for a hot street motor of 383 to 420-ci displacement.
The exhaust port is equally respectable with near-90 percent low-lift E/I numbers that equate to allowing the engine to RPM without backing up the exhaust flow and causing pumping losses at higher engine speeds. Overall, we think this is an excellent choice for either a larger displacement smallblock like a 383 or 406, or even a 355 with a larger camshaft where you’re willing to spin the engine a little higher to make power.
Dart Pro 1 215 Aluminum
We should probably call the Pro 1 series Dart’s “Version 1” as well since the company has upgraded its entire Pro 1 series aluminum heads over to Platinum status. The Pro 1 series is still a solid choice. Again, in comparison to the later Platinum head of the same port size, it’s not quite as good and would probably not perform as well on an engine because the Pro 1 has not benefited from the wet flow modifications. As with the previous Pro 1 versions, this is still a front half of the pack head. If you are interested in this size head in aluminum, the Platinum version is an excellent choice.
Edelbrock Victor Jr. 215 Aluminum
Since Edelbrock tends to emphasize small-port velocity numbers over high-lift flow, this approach tends to obscure this head as a decent performance small-block cylinder head. Many performance enthusiasts don’t even know that Edelbrock offers an aggressive small-block head. In keeping with Edelbrock’s port velocity concept, the Victor Jr. intake port is a comparatively tight 2.05 sq.in., smaller than all the other 215-cc intake port heads, and smaller than a few of the 200-cc intake ports. You can probably guess where this is headed. The intake port CFM numbers may not be overly impressive compared to other 215-cc heads, but don’t overlook its intake port velocity curve. The low-lift velocity numbers are not as strong as we might have expected, and the head’s performance at 0.300-inch lift is especially weak. This means that there is work that could still be accomplished in the throat and valve job area (perhaps with a 30 to 35-degree back angle on the intake valve) that would improve both the flow and the velocity.
The strength of the Victor Jr. Edelbrock head is its excellent port velocity curve. The flow numbers are decent, but combined with a smaller intake port cross-section, this pumps the velocity, which promises power.
Where the Victor Jr. does excel is at the higher lift points, especially at 0.600-inch lift where it actually exceeds the velocity sweet spot of 130 cfm/sq.in. This obviously means it would require a camshaft with 0.600-inch lift or more, which puts it on the ragged edge of a streetable combination. An application where this might work is a larger-displacement small-block in the 410 to 430 ci range. This velocity could contribute to a killer power curve, taking advantage of the small-block’s torque based on displacement rather than RPM potential.
On the discharge side, the Victor Jr. exhaust port offers a decent exhaust-to-intake flow relationship, which means it could use a camshaft with a slight amount of additional exhaust duration to be able to deliver maximum horsepower potential. In fact, the Victor Jr. serves up an excellent 80-plus percent E/I average all the way from 0.100 to 0.400 inch of valve lift. This contributes to purging the cylinder of exhaust gas long before the piston reaches BDC, which should reduce pumping losses. Because Edelbrock does not put 30- degree back-cuts on its heads, this is a simple modification that you could do that would probably benefit both the intake and exhaust flow and velocity aspects. Overall, this is a head that offers quite a bit of power potential and should not be overlooked.
Trick Flow Specialties has quietly been building a superb catalog of excellent cylinder heads for the small-block Chevy. To complement the Kenny Duttweiler signature 195- cc head, TFS has come up with a 215- cc intake port casting that offers excellent flow for the port cross-sectional area that makes its velocity curve one of the better ones in this category. With 2.08/1.60-inch valves and a 67 cc combustion chamber, this combination is intended for either a high-RPM smaller-displacement 355 ci small-block, or a larger-displacement 383/406/415-ci small-block that’s intended more for torque production than ultimate high RPM horsepower. Another excellent attribute is that these heads are also affordable with prices in the $1,500 to $1,600 range for a complete pair of heads ready to bolt on.
Brodix Track 1 215
This is an aluminum casting from the folks in Mena, Arkansas, that has been around for quite some time. As a result, its numbers are not quite as impressive as some of the later-developed heads. This places it at somewhat of a disadvantage, but we address it here mainly because you might run across a set at a swap meet or on the Internet for sale, and if the price is right, it could be a real bargain. It does flow well in comparison, for example, to the Dart 215 Iron Eagle and offers better exhaust port flow. Unfortunately, this first design Track 1 relies on a rather large port cross-sectional area in order to accomplish these flow numbers. This creates the slow port velocity numbers you see on our flow chart. For example, the Track 1 suffers from the same low inlet velocities at 0.300 to 0.400-inch lift just as many other heads in this category.
The Brodix Track 1 is another older intake port head that is still popular with some street engine builders, and its numbers indicate it’s a mid-pack runner.
The Track 1 does offer a decent exhaust port, although the E/I numbers are a little deceiving because the intake side is not quite as strong, making the percentage comparison for the exhaust look better. Still, this is not a bad cylinder head and the potential is there. It would be interesting to reduce the port cross-section by a couple of tenths of an inch and see if the port flow would remain the same. This would pump up the velocity and perhaps help this head, especially in the higher valve lift regions.
Quench is the clearance between the piston and cylinder head at TDC. It can affect engine effeciency and performance, if you truly understand it.
Cylinder Head Flow Data @ 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software