Head porting can result in very impressive power gain in a vehicle, especially when performed excellently by a skilled auto mechanic.
Cylinder heads, like 243 heads, have the ability to get more air and fuel into a vehicle’s cylinder, combust it efficiently, and exhaust it as smoothly/fast as possible.
This article unveils critical information about the 243 cylinder heads and why they seem to be one of the best heads with the capacity to boost power output. Take a moment to digest every section of this article in the next few minutes.
243 LS Cylinder Heads
Cast flash commonly happens while casting cylinder heads out of iron or aluminum alloy. This flaw develops due to metal leaking from cast joints and contact between the substance and the mold’s base while it’s still molten.
The cylinder valve seat and other cuts that were necessary for the cylinder head layout are milled out using CNC machining once the foundation material for the cylinder head is created. A rough cylinder head is produced when the design is finished.
Fluid passes through the head area and into the cylinder utilizing the valve throat as a channel, depending on the condition of the cylinder head.
The cylinder head must be machined to reduce the number of rough patches or minor constraints that can impair the fluid flow into the corresponding cylinder to achieve an adequate fluid flow that yields maximum performance.
The finer intake and quicker discharging from reduced fluid flow turbulence will increase power output. The 243 head porting is crucial for this reason.
The 243 cylinder heads from GM are third-generation cylinder heads created for performance applications, V8 trucks, SUVs, and vans. They are frequently known as LS6 heads.
The cathedral-shaped inlet ports and D-shaped exhaust on the 243 cylinder heads contribute to better air and fuel intake, smooth burning, and quicker exhaust. Improved horsepower is produced. As a result, they are leading to greater effectiveness.
243 LS Heads Common Problems
Although the 243 Heads are a great option for many LS engines, some common problems can occur. These include:
- The heads can crack near the exhaust port.
- The heads can warp or distort over time due to heat.
It is important to keep an eye on these problems and have them fixed as soon as possible to avoid any damage to your engine.
What Makes the 243 LS Heads Special?
Despite not being the newest or even best in the market, 243 heads are still a great choice, especially if you are on a budget. Here are some of the reasons that make the 243 heads special:
- The Cathedral intake port design helps to improve airflow into the engine.
- The smaller combustion chamber volume increases the compression ratio which can lead to more power.
- Oval-shaped exhaust ports help to increase exhaust flow out of the engine.
The 243 Heads have become common for use in drag racing due to their ability to make good power at high rpm.
Further, the 243 heads can be used on the LSX block and offer a smaller chamber for better compression. However, they will require expensive aftermarket pistons to work.
Thus, if you are looking for an upgrade from your stock LS heads or want to get more power out of your engine without breaking the bank, consider a set of 243 Heads.
243 LS Heads Features
The LS6 had a stiff valve train coupled with an aggressive camshaft that made it perfect for the Corvettes at the time. Ported 243 heads can still be used today due to their many highlighting features.
#1. Cylinder Block.
The cylinder block is the foundation of the engine. It’s where the pistons, rods, and crankshaft are housed. The block is also where you’ll find the oil pan and water jacket.
The 243 heads were initially designed for the LS6 engine, which had a smaller 4.8L displacement. The LS6 cylinder block has many similarities with the V8, such as a 4.4-inch bore center and a 90-degree angle.
#2. Rotating Assembly.
The assembly of an engine that rotates is called the rotating assembly. It consists of the crankshaft, connecting rods, and pistons.
The LS6’s rotating assembly includes a forged steel crankshaft and powder metal connecting rods. The pistons are made from cast aluminum and have a hyper eutectic design.
As a result, the LS6’s stroke is 3.62 inches shorter than the V8’s 4-inch stroke. It helps to create more torque at lower RPMs.
Meanwhile, the compression ratio of the LS6 is 10:1, which is higher than the V8’s 9.6:1 compression ratio. As a result, it helps the engine to produce more power.
#3. Cylinder Heads.
The cylinder heads are responsible for housing the intake and exhaust valves. They also have combustion chambers where the air/fuel mixture is combusted.
The 243 cylinder heads are made of aluminum with steel intake. The exhaust valves are at a 15-degree angle to maximize airflow. Other components of the 243 cylinder heads are roller-pivot rocker arms and beehive valve springs.
- Roller-Pivot Rocker Arms: A rocker arm is a lever that transfers motion from the camshaft to the valves. The LS6’s rocker arms are made of investment-cast nodular iron, with a 1.7:1 ratio. They also have needle roller bearings to minimize friction.
- Beehive Valve Springs: The beehive valve springs increase valve train stability at high RPMs. They are made of chrome silicone, and they can handle a lift of up to 0.550 inches.
#4. Engine Management.
The engine management system is responsible for controlling the air/fuel mixture, ignition timing, and idle speed. It does this by using sensors that monitor various engine parameters.
The LS6 engine is managed by the Engine Control Module (ECM). The ECM uses information from the following sensors:
- Crankshaft position sensor
- Throttle position sensor
- Mass airflow sensor
- Oxygen sensor
- Coolant temperature sensor
The ECM uses this information to make real-time adjustments to the air/fuel mixture and ignition timing. Thus, it helps optimize engine performance and fuel economy.
#5. Camshaft Design.
The camshaft is responsible for opening and closing the intake and exhaust valves. It also controls the timing of these events.
The LS6 camshaft is made of forged steel, and it has a duration of 204 degrees. The lift is 0.480 inches, and the lobe separation angle is 112 degrees. The camshaft design is similar to 241 heads.
#6. Intake Manifold.
The intake manifold is responsible for delivering the air/fuel mixture to the cylinders. It has a cast aluminum build and a runner length of 12 inches.
The intake manifold has a lower plenum and an upper plenum. The lower plenum is where the air enters the manifold, while the upper plenum is where the air/fuel mixture is distributed to the cylinders.
The intake manifold in 243 LS heads has a 30-pound-per-hour fuel injector. The results from this intake manifold configuration later became the standard for LS1 243 heads due to their effectiveness.
#7. 24x Ignition System.
All LS6 engines have a 24x crankshaft reluctor wheel. The wheel maintains a consistent relationship between the crankshaft position and the ECM. As a result, the ECM can provide accurate ignition timing control.
The LS6 also has a coil-near-plug ignition system. It means that there is one coil for each spark plug.
The coil-near-plug ignition system is more efficient than the conventional distributor ignition system. As a result, it helps to improve engine performance and fuel economy.
#8. Exhaust System.
The exhaust system removes the combustion gases from the cylinders. It consists of the following parts:
- Exhaust manifold
- Catalytic converter
- Muffler
The LS6 exhaust manifold is made of cast iron. It has a cross-over design, and it is connected to the catalytic converter with a stainless steel pipe. The catalytic converter is responsible for reducing emissions.
The muffler is located at the end of the exhaust system and helps in noise reduction. The LS6 engines have the same exhaust manifolds as their LS1 counterparts.
What LS motor has 243 LS heads?
The 2001 – 2006 LS6 engines came with 243 heads. This made the engines more powerful at the time.
If you are asking, “What did 243 heads come on?” The 243 heads were typically found in GM’s C5 Corvette; however, it was later ported and now found on engines like truck specs LQ4 and LQ9.
The LS6 was designed to work with the Corvette’s titanium exhaust system in order to deliver extra power. It also had an incredible camshaft, stronger valve train, and other sophisticated enhancements that made it one of the best vehicle engines.
243 LS Head: Is Better For Your Engine Build?
#1. Basic Specifications and Origins.
The 243 heads are a high-flow option designed to deliver superior performance. They were originally introduced on the performance-oriented LS6 engine found in the Corvette Z06 (2001-2004) and later used on LS2 engines.
With a slightly larger combustion chamber volume of 64-65 cc, they balance compression and compatibility with forced induction.
These heads feature larger 2.00″ intake valves and 1.55″ exhaust valves, supporting higher airflow and RPM performance.
#2. Combustion Chamber and Compression Ratio.
The 243 heads, with their 64-65 cc combustion chambers, balance increasing compression and maintaining compatibility with forced induction.
On smaller displacement engines like the 5.3L, the slightly larger chamber reduces compression compared to 862 heads, which can slightly soften low-end torque.
However, this reduction is generally minor and is offset by the superior airflow characteristics of the 243 heads, which shine at higher RPMs.
On naturally aspirated builds, the moderate chamber size of 243 heads provides a compression boost over larger truck heads like the 317 or 706, making them a popular choice for maximizing horsepower and efficiency.
When used with forced induction, their slightly lower compression compared to 862 heads offers a safer margin for higher boost levels without sacrificing too much off-boost performance.
These features make the 243 heads a versatile option for builders seeking a balance of power, reliability, and flexibility, whether in naturally aspirated or boosted configurations.
#3. Port Design and Airflow.
The 243 heads are celebrated for their top-tier cathedral port design, which supports excellent airflow and performance across a wide RPM range.
With larger intake valves (2.00″) and optimized port geometry, these heads deliver superior intake flow, making them a natural choice for high-performance builds.
The intake port design allows for greater volume and velocity, enabling stronger cylinder filling and higher power output, particularly in the mid to high-RPM range.
On the exhaust side, the larger ports and refined shape enhance scavenging, which supports better overall efficiency and power.
This improved flow makes the 243 heads a favorite among naturally aspirated builds aiming for maximum horsepower and torque.
They also handle moderate forced induction well, as their superior port design ensures consistent performance even under higher cylinder pressures.
While the 243 heads excel in high-performance applications, their focus on top-end flow can result in a slight trade-off in low-end torque when used on smaller-displacement engines.
However, this is often mitigated by pairing the heads with a camshaft and intake manifold tuned for balanced performance.
#4. Typical Power Potential and Use Cases.
The 243 heads are designed with performance in mind, offering a significant upgrade in power potential compared to the 862 heads.
Their larger valves and superior port flow allow for strong cylinder filling, particularly in mid- to high-RPM ranges. This makes them ideal for high-performance street cars, strip builds, and road course applications.
243 heads can support impressive horsepower gains in naturally aspirated setups.
Many enthusiasts report reaching or exceeding 500 horsepower on LS engines with properly tuned combinations. They are also capable in forced induction applications, handling moderate boost levels while maintaining consistent flow characteristics.
However, their smaller combustion chambers compared to larger truck heads like 317 or 706 mean that tuning and premium fuel are often necessary to manage compression under boost.
The primary drawback of 243 heads is their cost and availability. Their popularity among LS enthusiasts has driven up demand, making them more expensive than other OEM castings.
Also, for budget-conscious builders working with smaller displacement engines like the 4.8L or 5.3L, the flow potential of 243 heads may be underutilized without additional modifications to the bottom end or supporting components.
#5. Cost, Availability, and Machining Considerations.
The 243 heads are among the most sought-after LS castings thanks to their reputation for performance and versatility. This demand, coupled with their limited availability compared to truck heads, drives up their cost on the used market.
Clean sets of 243 heads, particularly those with upgraded valves or springs, often command premium prices, which can be prohibitive for budget-conscious builders.
Despite the higher upfront cost, the 243 heads offer strong performance right out of the box, often requiring minimal machining to fit most performance applications.
Naturally aspirated builds typically only need a basic valve job or upgraded springs to pair with a more aggressive camshaft.
In forced induction setups, milling may be necessary to adjust compression, but the smaller chamber size of these truck heads already provides a higher starting point than larger truck heads.
Given their high flow potential and performance pedigree, the cost of 243 heads is often justified by the gains they deliver.
However, their premium pricing makes them best suited for builds where maximizing top-end power is a priority, and the budget allows for complementary upgrades to fully leverage their capabilities.
#6. Common Complaints and Drawbacks.
The biggest drawbacks of 243 heads are their high cost and limited availability. However, LS enthusiasts, particularly those looking for a plug-and-play performance upgrade, highly demand these castings.
This demand inflates prices, making 243 heads a premium option compared to other OEM castings. For builders on a budget, the upfront cost may be difficult to justify unless top-end performance is a priority.
Another issue is that the flow potential of 243 heads can be overkill for smaller displacement engines or mild builds.
The heads’ capabilities may not be fully utilized on stock 4.8L or 5.3L engines with factory cams and intakes, resulting in a less noticeable performance gain.
Also, their slightly larger combustion chambers can reduce compression when directly swapped onto smaller engines, potentially softening low-end torque without further modifications.
Lastly, 243 heads often require precise tuning to optimize performance and avoid detonation, particularly in forced induction setups or naturally aspirated builds running aggressive cam profiles.
While the tuning requirements are a reasonable trade-off for their performance, they do add complexity to the build process.
#7. 243 Head for Your Build?
The 243 heads are the go-to option for performance-focused LS builds, especially on 5.3L, 6.0L, LS1, or LS2 short blocks.
Their larger valves and high-flow ports unlock significant mid- to high-RPM horsepower, making them ideal for street/strip cars, road course vehicles, and naturally aspirated builds chasing maximum efficiency and power.
If you’re planning moderate forced induction, 243 heads provide a good balance of flow and chamber size to handle boost without compromising too much on compression.
They’re also popular for enthusiasts seeking to replicate or surpass LS6-level performance with minimal modifications.
The higher cost of 243 heads is often justified by their out-of-the-box capabilities and potential to support ambitious power goals.
However, they’re best suited for builders with the budget to match these heads with a performance camshaft, intake, and exhaust system that can fully utilize their airflow advantage.
Is 243 LS Head Any Good?
Of course, the 243 head is designed with a better casting which has a smaller chamber for more compression. They flow better and have the capacity to deliver more than 5% horsepower on flow alone.
If you desire to perform a porting on your vehicle’s cylinder head, getting new 243 heads is perfect for the porting job.
When the 243 heads are coupled with a powerful can and an excellent valve lift, the result is improved power output. If you’re looking for 243 heads for sale, kindly check a dealership near you or buy online.
FAQs.
Q: How much HP do 243 heads add?
A pair of 243 heads add up to about 20 horsepower (hp) on the GM’s bolt-on LS1 or LS6 engine. Since the engine already features an aggressive camshaft, it might experience a little bit more horsepower.
If you desire to modify your vehicle’s internal combustion engine intake and exhaust ports, swapping to 243 heads alone can be a great enhancement. With this, you can enjoy improved airflow, which in turn adds up more horsepower.
Of course, a porting job coupled with a high-performance cam and an excellent valve lift can trigger an incredible potential for improved power output.
Q: Are 243 heads better than 706 heads?
243 heads are pretty much better than 706 heads. They feature 2.0” intake valves, as well as a 1.55” exhaust. On the other hand, the 706 heads come with 1.89” intake valves and 1.55” exhaust, respectively.
The 243 heads come with 64.5cc chambers, while the 706 heads feature 61.5cc chambers. Although the 243 heads appear to be more excellent than the 706 heads, it may not be a nice combo with a tiny bore engine due to its larger intake valve.
Q: What are GM 243 heads?
GM 243 heads are General Motors’ 3rd generation cylinder heads designed for V8 trucks, SUVs, vans, and performance applications. The 243 heads are often called LS6 heads because they were found on the 2001 – 2006 LS6 engines.
The 243 heads have a D-shaped exhaust and cathedral-shaped intake ports. The cylinder heads combustion chamber is smaller than the earlier cylinder heads fitted on LS1 engines. 243 is also more efficient than the earlier heads found on LS1.
Q: What do stock 243 heads flow?
The GM stock 243 heads are designed to boost flow by up to 32.2 cfm and 28.5 cfm on the intake and exhaust sides, respectively. The 243 heads release about 5% more power on their flow alone.
The power enhancement is because of its hollow valve stem, which delivers a better RPM potential, standing up to more turbo or supercharger applications. 243 heads were improved with more flow and a little bit more compression than LS1 heads.
Q: What is special about 243 heads?
The 243 heads are unique for the top-notch performance and awesome feeling they bring to the table. The satisfaction you derive from using 243 heads cannot be matched.
The 243 heads are designed to deliver extra boost and increased performance due to the more excellent casting and better flow, incredible design, and relatively nice marginal gain compared with its price.
With a flow boost of up to 32.2 cfm and 28.5 cfm on the intake and exhaust sides, respectively, and a horsepower boost of up 20 hp, the 243 heads stand out among others.
Q: How much does HP gain from port and polish?
Porting a vehicle’s cylinder heads can improve the horsepower gain up to about 25 HP more compared to its original stock setup.
However, the cylinder head’s original state and the quality of the auto mechanic’s workmanship in porting the heads are factors you must consider.
Therefore, it is crucial to consult an expert auto mechanic who has a series of past experiences in porting cylinder heads. A perfect port and polish should deliver an incredible horsepower gain to improve your vehicle’s performance.
Q: Did the 5.3 come with 243 heads?
Of course, the 5.3, as well as the 4.8, come with factory-designed 243 heads nowadays. The LS6 engine, designed between 2001 and 2006, came with 243 heads.
You can ascertain the 243 heads on 5.3 by checking the stamping with three digits near the valve cover.
Meanwhile, the GM’s Sierra 1500 and Silverado manufactured between 1999 and 2013 came with 243 heads. Vehicle engines exert so much power with high performance and efficiency due to the cylinder heads that they carry.
Q: Are 243 heads Cathedral port?
Yes, the 243 heads have a cathedral-shaped intake port, offering smaller chambers than their rectangular port counterpart. The 243 head compression ratio is capable of enhancing power output by 3 to 4 percent, running up to 25 horsepower.
The 243 heads are a perfect choice if you desire to carry out a porting job. Swapping to 243 heads alone can boost horsepower tremendously.
However, the presence of an aggressive cam and a nice valve lift can deliver more excellent power output for high performance and efficiency.
Final Words
Important information about the GM 243 heads has been critically unveiled. You’ve learned the essence of having incredible cylinder heads in a vehicle. Vehicle enthusiasts argue about 243 heads Vs. 799, as well as 243 heads Vs. 862 heads.
However, if you desire improved horsepower with excellent power output, the 243-cylinder head is a perfect choice. Meanwhile, you must contact an expert auto mechanic with an intensive understanding of performing the porting job.