Budget Big-Block Cylinder Heads You Need For Your Engine

When it comes to building a lot of horsepower, are more cubic inches the only way to go? The big-block Chevy has been around for decades, and not only was – but still is – the engine of choice for many hot rodders. Building an engine with big power means choosing each of the component parts wisely. Heck, even when building a reliable street/strip engine, the wrong choice of parts can result in an engine that doesn’t perform as you hoped.

When looking at cylinder heads, you have a lot of choices. Some guys are still scouring swap meets to find used cast-iron airflow directors. However, when most enthusiasts are looking to upgrade or build a big block, aluminum heads are typically one of the first upgrades. Luckily, the aftermarket is flush with different offerings, many of which can fit into relatively tight budgets.

The Edelbrock 60455 Performer RPM O-Port cylinder heads are perfect for street performance, daily drivers, street rods, and muscle cars. These cylinder heads deliver great throttle response and power from 1,500 to 6,500 rpm. At $1,986.60 a pair, they are great upgrade.

When you are assembling an engine, one of the worst things you can do is focus on “less expensive” parts. Instead, you should focus on proper usage parameters. Buying certain parts just because they work great on your buddy’s car might actually cost you more in the long run. To get you some solid input, we reached out to Eric Blakely of Edelbrock Performance, Mark Campbell of Racing Head Service, Jack McInnis of World Products, and Tim Torrecarion of Air Flow Research (AFR) and got some solid advice about choosing cylinder heads.

With some smart-shopping techniques – like knowing what your overall engine goal is – you can purchase a set of big-block cylinder heads without breaking the bank or compromising power output. Campbell agrees, “The most important factor is knowing the intended use for the combination. A street engine that will see a lot of low- and mid-range RPM is very different than a drag race engine that is run at peak RPM for short times. Also, knowing as many details about the engine (bore and stroke, compression, and whether using boost or nitrous) are very important when selecting the right head design for the job.”

To help you decide what big-block Chevy heads are right for you, we have assembled a guide that will help you make an informed choice. This guide to budget-friendly big-block Chevy heads will be limited to assembled units that are great choices for street and street/strip use, and are sold as a set for less than $2,500.

Aluminum VS. Cast Iron

Aluminum heads are hard to beat when it comes to performance, but cast-iron heads are still a viable option for restoration or certain performance needs. “Probably the biggest reason to choose cast iron, would be because of cost, or if you had to follow some type of rules for a certain class of racing,” said Campbell. “An aluminum head is a bit more costly, but will typically outperform a cast-iron head because of its ability to dissipate heat and reduce detonation. Also, if damaged, they can be much easier to repair as well.”

The biggest advantage aluminum has over cast, is its lighter weight when compared to cast iron. The fact it dissipates heat very quickly, may or may not be an advantage, depending on what you are trying to achieve. McInnis concurred, “Iron heads can offer great performance at a much lower cost than aluminum in any application where weight is not critical. Street cars or heavy street/strip cars are good candidates.”

When the big-block engine was introduced in the mid-1960s, the heads had closed chambers (Left). In 1969, Chevrolet introduced the open-chamber design (Right). This change offers better combustion in the chamber. The new open-chamber design was larger (118 cc, as compared to closed-chamber heads at 101 to 109 cc).

Closed Or Open Chamber?

You hear this description thrown around quite often, but what is the design reasoning of each? An open chamber head will have a larger combustion bowl/chamber, which opens more area around the valves. An open chamber head can be identified by the recessed area of the chamber extending the diameter of the cylinder bore.

A closed chamber is much smaller than the cylinder bore. It does not extend the entire diameter of the cylinder. The smaller combustion chamber results in the head’s deck surface extending into the combustion chamber area. This forces the air/fuel mixture into the smaller combustion chamber when the piston is on the compression stroke.

Dart Iron Eagle 308cc cast-iron heads are great for street/strip performance. The heads are designed to deliver power through 7,000 rpm in engines with less than 500 cubic inches. They provide excellent mid-range torque and power, and are good for heavy vehicles. They do feature a higher-than-stock exhaust port (.300-inch). If you already have headers, this could cause clearance issues. Cost is $1,908 for a pair.

 

How do you know if you need an open or closed chamber design? “Chamber volume is the key to getting the engine’s compression ratio where you want it, when matched with the right piston dish/dome volume, block-deck height, and other factors,” said Campbell.

McInnis added, “What you are looking for is a compression ratio suited to your engine and its intended use. Other than very high-end race heads, most big-block Chevy heads have chambers around 119 to 120cc, so the choice is more one of piston design for street/strip engines.”

Finally, if you are looking for a closed-chamber head, you will need to use an OE cast-iron unit. Nobody makes an aftermarket closed-chamber head. Experts agree the power building-potential of open-chamber heads is significantly better than those with closed chambers. That is why all aftermarket heads are made with open chambers.

AFR’s 265cc Magnum heads have an oval-port design, and feature partially CNC-ported chambers, intake, and exhaust ports. These are recommended for smaller cubic-inch engines (396 to 468ci) used for street, towing, or street/strip, operating up to 6,200 rpm. We found them for $2,199 a pair.

Intake Port Shape And Size

It’s no secret that a larger port has the potential to flow more air than a smaller port. But, how much flow your engine needs will vary depending on engine requirements. The size of the intake port and runner is a very important issue when it comes to head design.

“Flow numbers matter, as you need to know how much air will be able to move through the cylinder head to make a given amount of power. But, it is certainly less important on a street engine,” Campbell assured. “For a street engine, the air speed [velocity] in the intake runner matters the most, and this is more related to the size of runner in the head. Keeping air speed high, makes an engine more responsive in the low- and mid-RPM range. It will also make the signal to the carburetor stronger, resulting in better overall performance.”

big-block cylinder head

In stock form, oval-port heads (Top) are capable of flowing enough air to support roughly 600 to 650 horsepower. Rectangular-port heads (Bottom), were designed primarily for engines that spend much of their time at higher RPM. (Image courtesy of www.chevydiy.com)

Runner volume (length) is also a very important consideration. For example, a street engine will spend most of its time at low-RPM cruising, and typically utilize a small-lift camshaft. In this application, performance will be less than optimal if the cylinder heads have large-volume intake runners. The reverse is also true. High-revving, big-lift camshafts in engines with big displacement will not like smaller intake ports.

While a larger intake runner will allow more airflow, that larger area will also decrease the velocity of the moving air and fuel. Smaller runners will not deliver as much air, but will speed up the flow. The latter, actually improves throttle response and torque. Keep in mind, the improved throttle response at low- and mid-RPM will sacrifice peak horsepower, as it will not deliver the maximum amount of air and fuel that your engine needs when the pedal is floor-boarded. You need to find a perfect balance of good flow and velocity for your intended usage.

big-block cylinder head

The World Products Merlin head is a cast-iron unit. Its rectangular-port design is available with intake ports of 320cc and 345cc configurations. Complete assemblies feature multi-angle valve jobs, Erson stainless-steel valves, and valve springs matched to camshaft requirements. A pair will set you back $1,691.

There are differences in the BBC head’s intake port shape: rectangular and oval. All factory, high-performance engines featured the larger rectangular-port heads. These have higher airflow rates than production oval-port heads. But, the larger volume of the rectangular ports can be detrimental on a street engine, as the design produces slower velocities at low speeds. The smaller, oval-port heads are typically a better choice for a daily driver or street/strip car.

“Flow numbers are meaningful in a street engine, but the low-lift flow numbers will be more meaningful, ” said McInnis. “That is because the more streetable camshafts will not have extremely high lift. If you buy heads that flow a gazillion cfm at .750-inch lift and your cam only has .450-inch lift… you get the picture. Oval port heads with relatively small intake runners work very well for street engines and small displacement big-blocks, because the oval ports will maintain good velocity in the airflow, and that promotes better fuel atomization. Larger and more aggressive engines will benefit from the bigger rectangle-port-style heads.”

big-block cylinder head

There are many different intake runner volumes available, and chances are, only one or two of them are appropriate for your engine application. When it comes to deciding which heads to use, you need to make a realistic judgment of your intended usage for your vehicle. Most experts will agree that bigger is not always better.

Typically, a bigger valve, port size, and runner volume are desired in higher-performance applications. However, knowing this guide is directed at street/strip cruisers, you will want to look for a runner volume in the range of 290cc to 360cc.

The Final Word

It’s been said that using the words “budget” and “big block” cannot be used in the same sentence. In fact, many feel it is an oxymoron. However, the cylinder heads we’ve listed are well within the range of what can be considered budget friendly.

big block cylinder head

These fully assembled Pro Action heads from RHS, come with valvetrain components for use with hydraulic-roller cams delivering lift numbers up to .600-inch. The runners are large, at 360cc. These are definitely for the serious street/strip car, and a pair will cost you $2,400.

Whether you are resurrecting a salvage-yard engine or you want to upgrade your daily driver because you have aspirations of occasionally taking it to the drag strip, one of the heads we’ve listed could be just what your engine needs. Before you plunk down your hard-earned cash though, we encourage you to call the tech lines these manufacturers have available, or work with your engine builder.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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