With so many cylinder heads to choose from, how do you know which one is right for your small-block Mopar? Our small-block cylinder head guide will take the guesswork out of choosing the right head for your combination.
Back in the early days, choosing cylinder heads for your small-block Mopar engine used to be a no-brainer. If you were on a budget, you'd simply freshen the factory steel heads and, perhaps, perform some port and bowl work, top them off with stiffer springs matched to the camshaft you chose, and try to be happy with the power the heads made. If your wallet was a little thicker, you'd search the boneyards for a set of X or J castings, perform the same work, and be a little happier with the output of the engine. For die-hard racers with deep pockets, the Direct Connection W-2 casting was the cylinder head of choice, but it came with baggage. The W-2 needed special valvetrain components, a special intake, and the exhaust ports required either special custom-built headers or adapter plates, so this option was really only feasible if you were professionally racing your Mopar. Well, times have changed and in the last decade or so the aftermarket has become flush with cylinder heads for your small-block Mopar. There are so many cylinder heads, in fact, that choosing the right one for your application has become a confusing proposition.
We at Mopar Muscle are here to help. If there's one thing we hate to see it's a nice car that doesn't run up to its potential due to improper matching of parts. If you're building a stock street motor for weekend cruises, it just doesn't make sense to use a large port, giant valve race head. In fact, too much head for an application will nearly always equate to poor performance and decreased economy. Matching the cylinder heads to your combination is equally important in a race engine. There's just no way that a factory production head will flow enough air to support a high cubic-inch small-block at high rpm no matter how big the cam or how extensive the port job. Actually, the cylinder head choices for bone stock or full race applications probably require less thought than for your application as there are fewer cylinder head choices at those ends of the spectrum. Chances are your project falls somewhere in between a stock engine and a full race application, which gives you dozens of cylinder head choices. Careful planning and setting a performance and budget goal for your build are the first steps to making the proper cylinder head choice. You may find the heads you already have will achieve your performance goal, but your budget will allow an aluminum head saving weight and giving you additional performance. On the other hand, your budget may dictate the race heads you desire are out of reach, requiring that you make the best of your factory units. Either way, this article should help you make your choice.
We'll outline small-block cylinder heads and their performance potential to help make your decision easier. We'll begin with the factory production heads and work our way to the higher flowing, more exotic (and more expensive) race units. Remember that more than one cylinder head may meet all your requirements, so then the choice is up to your personal preference. Some heads are also cast in both steel and aluminum, so weight versus cost could be the determining factor in your decision. If you're a racer, be sure to consult the rules of your sanctioning body as they may dictate one or more cylinder heads that are legal for the class you race.
Large intake ports make factory Chrysler cylinder heads, such as the popular X casting shown here, good performers for mild to moderate applications. With port work and proper camshaft selection, we've seen these heads make upwards of 400 hp on a moderately prepped 360 short-block.
Factory Chrysler Cylinder Heads
The Chrysler LA (light A) engine began production in 1964 as a derivative of the poly 318, and since that time many cylinder head variations were produced. For the purpose of this article, we won't go into the many different casting numbers assigned these heads, but rather break them down into a few basic categories and concentrate on the ones best suited for mild, moderate, or race applications. The two basic types of early cast-iron production cylinder heads are differentiated by their port and valve sizes.
Early factory heads
Early 273 and most 318 engines utilized small port castings and are most easily identified by their 1.75-inch intake and 1.50-inch exhaust valves. The larger port 340 and 360 heads came with 1.60-inch exhaust valves and either 1.88- or 2.02-inch intake valves. For a mild street application or restoration, the small valve/small port cylinder heads will work fine,, but power will always be limited. We don't suggest the small port heads if you're planning to make any more than 300 hp because the machining required is cost prohibitive. Also, while outwardly the '64 and '65 273 heads have the appearance of the later 273 and 318 units, they may not be interchanged without also changing intake manifolds due to the intake bolt holes being machined at a different angle. While we don't seek out the 273/318 heads for performance builds, we do keep our eyes open for the older 273-4bbl. engines as they had mechanical valve gear that can be used in the later cylinder heads.
The main drawback to the X, J, and 915 castings is the open-style combustion chamber as shown here. These heads do provide good flow for a stock casting, but more power can be attained by using heads with a closed, quench style, combustion chamber.
The 340/360 large port cylinder heads are much more desirable factory units for a performance build. These heads are most often found with the 1.88-inch intake valves, but were also produced with 2.02-inch intake valves in 1968 through 1971. The notable "X" and "J" heads (named for an X or J cast into the head near the spark plug hole) fall into the large port category, as do cylinder heads with "915" as the last three digits of the casting number. AAR and TA E-bodies with the 340 6-barrel option, while sharing the same casting as other X and J heads, were machined for relocated push rods and required special valve gear. It's rare to find these heads today as they were very limited in production. Regardless of the casting number, the large port heads all offer similar potential and are the best of the early small-block cylinder heads. The drawback to these heads, however, is their open-style combustion chamber. In mild applications the X/J casting heads work great, flowing enough air to easily support most street engines and mild bracket race combinations. If more power is required, the later swirl-port or magnum heads would be a better choice.
Pictured here are the swirl port (closest), magnum, and Edelbrock Performer RPM cylinder heads. Notice the closed combustion chamber of the swirl port head, which greatly increases its power potential. Even with relatively small valves, the swirl port design head will make more power than X or J castings simply due to the better combustion chamber design.
Swirl Port Heads
Chrysler's small-block cylinder head design changed very little until 1987 when the 302 casting (last three digits of the casting number), commonly known as the swirl port, was introduced. While the 302 casting, as well as the later 308 casting, were most commonly found on low-performance 318s, they shouldn't be overlooked for a performance build. Even with small 1.75-inch intake and 1.50-inch exhaust valves, the design of this head's heart-shaped quench-style combustion chamber makes it a good choice for mild to moderate performance. An engine with these heads in stock form will outperform an engine with stock X or J castings simply due to the improved combustion chamber design. Additionally, these heads have hardened valve seats, which make them compatible with unleaded fuel. The swirl port heads were utilized through 1991 (302 casting) and 1992 (308 casting) and respond well to port and bowl work, offering better power potential than all of the earlier small-block heads. Another nice feature of these heads is they utilize valvetrain and intake manifolds common to early small-blocks, so parts are readily available. Simply bolt these heads to your small-block and enjoy the extra power they provide.
Magnum Heads
Introduced in 1992, Chrysler's Magnum engines are the epitome of factory produced small-blocks. Available in 318 and 360ci displacements, these engines can be found in thousands of Dakota and full-size Dodge trucks produced from 1992 to the present. While the Magnum short-block remains very similar to the 318 and 360 engines of old, the cylinder heads offer some advantages that aren't seen in previous small-block cylinder heads. The combustion chamber of these heads offers a double quench area, capable of higher power output than factory heads of the past. These heads also offer large 1.92-inch intake and 1.60-inch exhaust valves and larger port size than the earlier swirl port castings, making them the best factory produced cylinder head for a performance build.
Magnum heads can be bolted onto your non-Magnum LA engine, but there are several differences you should be aware of. First, the 60cc chamber size of the Magnum head is likely some eight to ten cc's smaller than the chamber of the head you're replacing, so the compression ratio must be factored. Next, the Magnum head uses pedestal rockers instead of the tried and true shaft mount system of old. These rockers are a good design, but are oiled via the tappet and pushrod so they require that the lifters be changed to AMC units with oiling provisions. Pushrods also need to be changed to hollow units for the same reason. An additional difference is the angle the intake manifold bolt holes are drilled into the head. Magnum heads require that a Magnum specific intake be utilized, which adds cost. Head bolt length is also different from the older LA heads, so Magnum head bolts must be utilized as well.
Even with the differences it is well worth using the Magnum head for your performance or race small-block build. These heads are readily available and offer the best power potential of any factory-produced head. Intake manifolds and performance rockers are available from several aftermarket companies and really wake these cylinder heads up. Magnum heads also respond well to port and bowl work, making these heads an excellent choice for your next small-block build.
Aftermarket Small-Block Cylinder Heads
Whenever a car manufacturer designs a product that works as well as the Chrysler small-block, the aftermarket follows by offering products to improve performance for the enthusiast. Such is the case with the Chrysler small-block. Once limited to the X or J castings for our builds, we now can choose cylinder heads from Mopar Performance, Edelbrock, Indy Cylinder Head, and Brodix for our engine build. While aftermarket cylinder heads do cost substantially more than a factory head found in the scrap yard, the additional performance can be worth it. Chrysler engineers in the early '70s realized that one of the biggest limitations to the small-block head's flow was the design of the intake port. By relocating the pushrod holes, utilizing special rocker arms, and designing larger, oval intake ports, the W-2 cylinder head was developed for racing applications. This head is still produced and used by many small-block racers today.
Mopar Performance
Mopar Performance offers an aftermarket cylinder head for any level of performance you wish to achieve. Magnum castings are available in cast iron, aluminum, and R/T trim, all of which outflow the factory Magnum heads. They even offer a Magnum head that can be used with pre-Magnum intake manifolds. Additionally, the Mopar Performance Commando cylinder heads are bolt-on replacements for early small-block heads. The Commando head uses the pre-Magnum intake manifold and utilizes factory shaft mounted valve gear. The Big-Port Commando offers substantial gains in flow and potential power through relocated intake pushrods but requires W-2 valve gear. The Big-Port Commando is drilled for both factory and W-2 exhaust making it a good replacement for both stock and older W-2 applications. The W series of Mopar Heads are bred for racing and offer much higher flow than factory replacement heads. High compression and aggressive cam profiles are needed to optimize these cylinder heads, but the results can be amazing. We've seen upwards of 800 hp produced by large cubic-inch small-blocks with W-9 heads, so these are definitely a good choice if maximum power is your goal.
Edelbrock
Edelbrock's aluminum cylinder heads are a great upgrade for your small-block engine. These heads offer an advanced combustion chamber and increased port volume, allowing them to outperform any factory production cylinder head. Intake valve size is 2.02 inch and the exhaust valve measures 1.60 inch, making these heads a good choice to replace factory units. These heads are available in either pre-1991 or Magnum trim, and are a cost effective way to save weight and increase performance. We've found the Edelbrock heads to be responsive to port and bowl modifications and to be a great all-around performance cylinder head for the street or strip.
Indy Cylinder Head
When it comes to Mopars, Indy Cylinder Head has long been known for making reliable horsepower. Boasting intake flow numbers of well over 300 cfm, their 360-1 and 360-2 cylinder heads are no exception. Utilizing the same long-valve technology that made their big-block heads famous, Indy has combined high-flow numbers with a heart-shaped, quench-style combustion chamber to produce a state-of-the-art small-block cylinder head. Additionally, these heads will bolt to any stock or aftermarket block and are machined for both factory or W-2 exhaust flanges. The 360-1 head utilizes a rectangular port, while the 360-2 utilizes an oval port that is compatible with W-2 intake manifolds. Both heads use large 2.10-inch intake and 1.65-inch exhaust valves, giving them great potential for large cubic inch or high horsepower applications. These heads do use different valvetrain hardware and intake manifolds than factory units, so they require additional parts to make them work. Indy has taken the guesswork out of utilizing these heads by offering them in a kit form, which includes everything from the block to the carburetor. these heads are a little more costly than factory units, but in our experience, you get what you pay for. If you want optimum power from your small-block, we highly recommend Indy's 360-1 or 360-2 cylinder heads.
Indy's 360-1 aluminum cylinder head utilizes a long-valve design similar to their big-block heads. These heads will fit a stock block or the Mopar Performance "R" series blocks and offer the potential for more than 700 hp.
Brodix Cylinder Heads
The Brodix B1 line of cylinder heads has long been known for their ability to produce power and the small-block B1/BA is no exception. In standard form, these heads offer impressive flow numbers, which are even more impressive in ported form. The standard B1/BA head uses factory style provisions for mounting intake and exhaust manifolds, and sports a relocated spark plug for more efficient combustion. These heads will bolt to factory or aftermarket blocks, making them a good choice for any performance build. Realizing the trend toward big cubic inch, stroked small-blocks, Brodix even offers a moved centerline version of this head, which utilizes giant 2.14-inch intake and 1.60-inch exhaust valves. Standard BA versions use factory Chrysler style intakes, while the moved centerline version utilizes the W-5 or W-7 style intake. Moved centerline heads can be drilled for either standard or W-2 style exhaust flanges. All of the B1 heads have a thick deck that is well suited to nitrous-oxide applications.
So there you have it, hopefully, we've cleared up any confusion regarding small-block Chrysler cylinder heads. As you can see, there are many choices when it comes to heads for your small-block, so set your performance goals and choose wisely. Whether mild or wild, it's hard to beat the Mopar small-block for economical, efficient power.
Upcoming heavy breathing
We were intrigued with Indy's small-block offerings, so we decided to try them for ourselves. Stay tuned for a 440ci small-block engine build utilizing Indy's heads that will be featured in an upcoming issue!
