Cylinder heads are one of the most crucial components for determining the power, efficiency, and performance capabilities of any engine. And when it comes to GM’s LS engines, one of the most common upgrades is swapping out the factory heads for a set of 862 heads.
But what exactly are 862 heads, and why are they so common for LS engine builds?
862 heads are a type of cylinder heads that are sand-cast and have cathedral port intake runners with a volume of 200 cc . They have the same port and valve sizes as 706 heads, which are another type of stock LS heads . The only difference is that 862 heads are made of a stronger material than 706 heads, which are semi-permanent mold cast.
862 heads are common for LS engine builds because they are widely available and relatively cheap. They can be found on many 4.8L and 5.3L engines, such as LR4, LM4, and LM7 . They can also be used on some 6.0L engines, such as LQ4 and LQ9, with minor modifications. However, they are not compatible with all LS engines, especially those with larger bore sizes or higher compression ratios.
Are 862 heads the best choice for your LS motor and what benefits do they offer over stock cylinder heads?
862 heads are not the best choice for your LS motor if you are looking for maximum performance and power. There are other cylinder heads that offer better airflow and velocity, such as 243, 799, or 317 heads . These heads have larger port and valve sizes, as well as different intake runner shapes, such as rectangular ports . They can also handle higher boost and compression levels than 862 heads.
862 heads do offer some benefits over stock cylinder heads, such as being more durable and less prone to cracking. They can also improve the horsepower and torque of LS engines like the common 5.3L and 6.0L variants, especially with the right supporting mods, such as camshafts, intake manifolds, headers, and tuning. With 862 heads, these engines can produce 400-500+ horsepower, depending on the setup.
In this comprehensive guide, we’ll dive into everything you need to know about identifying, choosing, installing, and tuning 862 LS cylinder heads to maximize the performance of your LS build. We’ll cover:
- 862 head specs and key features
- How they compare to other LS castings like 706 heads
- Technical benefits of 862 heads
- Top LS engines to use 862 heads on
- Installing and tuning guide
- Where to buy 862 heads
Plus plenty more details that will help you get the most out of running these popular aftermarket LS heads!
Table of Contents
What are 862 Heads?
862 heads refer to a type of cylinder heads that are sand-cast and have cathedral port intake runners with a volume of 200 cc. They have the same port and valve sizes as 706 heads, which are also stock LS heads. The only difference is that 862 heads are made of a stronger material than 706 heads, which are semi-permanent mold cast.
The 862 casting number does not identify these as the fourth generation “LSX” style head with a high-flow, rectangular port design. That is a misconception that is often repeated online. The fourth generation “LSX” style head has a casting number of 823, not 862. The 862 heads have a cathedral port design, which is the same as the third generation “LS1” style head.
Some key features and specs on 862 cylinder heads are:
- 200cc intake port volume
- 61cc combustion chamber size
- 1.89″/1.55″ intake/exhaust valves
- Compatible with LS1, LS2, LS3, LS6, and LS7 style intake manifolds
- Works with standard LS valvetrain components
- Designed for rebuildable high-performance applications
The intake ports on 862 heads flow slightly less than the stock 243 heads that come on most 5.3L LM7 engines from the factory. However, the 862 heads have a smaller chamber size, which raises the static compression ratio by approximately 0.5 point on otherwise stock 5.3L engines. This can improve the power output and durability of the engine.
LS engines equipped with a set of 862 LS heads may see some gains in horsepower and torque across the entire RPM range compared to stock heads. However, the gains are not as significant as some other cylinder heads that offer better airflow and velocity, such as 243, 799, or 317 heads.
Upgraded valve springs are not required on the 862 heads in order to handle higher RPM operation and increased valve lift. They work with all the stock LS valvetrain components. However, some machining or modification may be needed to fit them on some LS engines, especially those with larger bore sizes or higher compression ratios.
862 Heads vs Stock LS Heads
One of the most popular uses for the 862 head castings is on 5.3L and 6.0L truck engines. This allows builders to get more power from the common truck LS motors while maintaining a mostly stock engine.
So how do 862 heads compare against the factory heads these engines come with?
The 5.3L LM7 crate engine from GM trucks feature stock 243 heads. 243 heads utilize small, rectangular intake ports that flow only around 210 cfm. They have 64cc combustion chambers and 1.89″/1.55″ intake/exhaust valves.
Here are some key differences when upgrading to 862 LS heads:
- 61cc vs 64cc combustion chambers – The smaller chamber size raises the static compression ratio by approximately 0.5 point on otherwise stock 5.3L engines. Combined with the improved material, this yields more durability.
- 200cc vs 210cc intake ports – The intake ports flow slightly less out of the box. Smaller ports mean the engine can maintain better velocity, allowing it to produce more torque.
- 1.89″/1.55″ vs 1.89″/1.55″ valves – The valves in the 862 heads have the same diameter as the stock 243 heads. This means they do not require any machining or modification to fit.
- Aluminum vs aluminum construction – Both 862 and 243 heads are cast aluminum. This means they have the same weight and heat dissipation properties.
So in summary, 862 LS heads offer performance advantages of higher durability, better torque, and easier installation. The stock 243 heads are not a big restriction for making power on otherwise stock 5.3L and 6.0L engines, but they may crack or warp under high stress or boost.
Technical Details on 862 LS Heads
Now that we’ve covered the basic idea of the 862 heads, let’s look closer at some of the technical details and design features that make them perform well.
Cylinder Head Design
The 862 heads are cast from A356 aluminum alloy rather than iron. This makes them lighter and more resistant to heat than the stock cast iron heads. The castings are CNC machined to smooth out the ports and chambers to under 63 Ra. This improved surface finish reduces turbulence and friction as air flows through the ports.
High performance multi-angle valve jobs are precision cut onto the seats. The bowls are hand blended to optimize flow and swirl. Stainless steel 1.89″ intake and 1.55″ exhaust valves are used to handle high RPM operation.
The valve seats and guides as well as the entire combustion chambers are CNC profiled. This significantly improves airflow and mixing compared to the stock cast iron heads.
Intake Port Design
The LS intake ports on the 862 cylinder heads have a cathedral port shape, which is the same as the third generation “LS1” style head. The port shape and volumes are optimized to produce good low and mid-lift flow while maintaining high velocity.
At .600″ lift the intake ports flow around 240 cfm at 28 inches of water. The intake ports have 200cc of volume, which is the same as the stock 243 heads. The intake flange on the 862 LS heads accepts stock LS1/LS2/LS6 manifold bolt patterns. So these heads work with standard LS intake manifolds making them easy to swap.
Exhaust Ports And Headers
The D-shaped exhaust ports on the 862 heads flow around 200 cfm at .600″ lift. This is slightly better than stock castings but still able to maintain good velocity for low and mid-range power.
The exhaust ports come CNC profiled and hand blended from the factory. With some mild porting they can flow well over 220 cfm.
Fitting headers is straightforward thanks to the stock LS exhaust manifold bolt pattern on the 862 castings. Popular brands like Hooker, Kooks, and others offer compatible LS swap headers to take advantage of the high flow exhaust ports.
Chamber And Compression Design
The 862 heads have a smaller combustion chamber size than the stock 243 heads. The chambers measure 61cc, which bumps static compression over 10:1 with a standard 3.622″ LS crankshaft. This can improve the power output and durability of the engine.
The compact, heart-shaped chambers on the 862 cylinder heads feature a quench pad to improve detonation resistance. The sides of the chamber are CNC machined to reduce hot spots and improve flow.
Top LS Engine Applications for 862 Heads
Now that we’ve covered the design and benefits of the 862 heads, let’s look at some of the most popular LS engine configurations running these castings.
5.3L LM7 Truck Motors
The 5.3L LM7 was used in millions of GM trucks and SUVs. They feature a tough cast iron block, hypereutectic pistons, and 3.780” bore. With some basic bolt-ons like a camshaft, the 5.3L can make around 400 hp on totally stock 243 heads.
Swapping over to a set of 862 LS heads unleashes the true potential of built 5.3L engines. They can support up to a 230/238 .600” camshaft, 11:1 compression, and intake/headers for over 450 wheel horsepower.
On a paired with a larger cam, the 5.3L engine really wakes up with 862 heads. They enhance the entire powerband, help it rev higher, and boost torque. Truck guys love the results when upgrading to these heads.
6.0L LQ4/LQ9 Performance
Like the 5.3L, GM’s 6.0L truck motors leave a lot on the table from the factory. Their iron 706 heads flow just 240 cfm out of the box.
Putting 862 heads on a 6.0L block with supporting mods can enable these larger displacement LS engines to make 550+ horsepower. The 6.0L responds very well to the improved breathing up top.
With the right camshaft, intake, and headers, the 6.0L transforms into a serious street/strip mill with 862 LS heads. Don’t be surprised to see over 600 hp from pump gas LQ4/LQ9’s with these castings.
LS1/LS6 For Boosted Applications
The LS1 debuted the LS architecture and came factory supercharged in the Corvette Z06 as the LS6. These 5.7L Gen III engines feature great flowing 243 castings from GM.
But for turbocharged or supercharged LS1 builds, the 862 heads really help optimize performance. The rectangular port design is perfect for forced induction applications. Combined with an upgraded valvetrain and dual springs, the LS1 can sustain over 800 hp on the right boost and fueling setup.
LS2/LS3 For Naturally Aspirated Power
For all motor LS power, the LS2 and LS3 engines love 862 heads. GM’s Gen IV 6.0L blocks came with 821 castings from the factory – not a bad stock head but still capable of more.
The excellent velocity and flow characteristics of the 862 cylinder heads make them a popular choice for naturally aspirated LS2 and LS3 builds targeting high revs. They support larger ports than the 821 heads while maintaining street-friendly power.
With upgraded valvetrain components, these 6.0L engines can stretch well over 7000 RPM and produce 550+ horsepower NA with the 862 castings.
High-Revving LS7 Applications
The LS7 is famous for being the largest factory LS displacement at 7.0L. It also came with incredible stock ported heads. But the LS7 loves being opened up and extended to higher RPM ranges.
For high revving LS7 builds, the 862 heads are an excellent high flow casting to take the place of the stock LS7 heads. They match well with the 7.0L’s 4.125″ bores and can support 720 hp NA applications.
The LS7 really wakes up over 7500 rpm with a set of 862 LS heads. And they are a popular choice for adding boost down the line as well.
Installing 862 LS Cylinder Heads
Now that we’ve covered the benefits and top engines for the 862 heads, let’s go over what’s involved to install them on your LS build.
Remanufactured Vs New Heads
You can source 862 heads brand new or opt for quality remans. New castings are great but more expensive. Remanufactured heads offer excellent value.
When remanufacturing 862 heads, machining equipment like Serdi valve seat cutting tools and Sunnen servo-driven cylinder hones are used to guarantee OE-level precision.
Fully remanufactured heads come with CNC ported bowls/chambers, milled decks, three-angle valve jobs, and updated valve seals. This process ensures reliable performance and longevity.
Parts Needed For Install
Along with the heads themselves, here are the key components required to complete the 862 head swap:
- Valve springs – dual springs with titanium retainers rated for .650” lift
- Head gaskets – multi-layer steel MLS gaskets
- Head bolts – torque to yield GM head bolts highly recommended
- Pushrods – adjustable pushrods if changing rocker geometry
- Rocker arms – 1.7 ratio recommended for street use
- Lifters – check for binding and upgrade if needed
Surface Prep And Installation
Once you have all the parts, here are the steps for installing 862 heads:
- Clean and inspect the block deck and 862 head bottoms for flaws
- Surface the decks and torque plates to ensure proper sealing
- Test fit the heads and check for binding, adjust as needed
- Lube head bolts and install with a torque wrench to GM specs
- Degree in the cams, verify valve timing events line up
- Install valves, keepers, seals, springs, retainers, pushrods
- Adjust rockers, check pushrod length is correct
- Install valve covers, prime oil system, verify proper flow
With the heads torqued down and valves adjusted, the 862 heads are all set! Then you can break-in the new valvetrain.
Tuning Tips With 862 LS Cylinder Heads
Bolting a set of 862 heads onto your LS engine is just the first step. To maximize their potential, you need to properly tune and modify the engine to take full advantage of the improved airflow.
Here are some key tuning tips to optimize LS engines equipped with 862 castings:
- Run at least 10:1 static compression to maximize power gains
- Can safely go up to 11:1 static with the right fuel on stock LS displacement
- Higher compression enhances low RPM torque and throttle response
- Choose a cam with .600”+ lift to utilize full intake flow potential
- Modify the LSA to optimize powerband for RPM range desired
- Aggressive lobes mandatory to achieve high lift; 118+ LSA splits help high RPM power
- Upgrade to dual valve springs for any cam over .600” lift
- Use lightweight titanium retainers to extend safe RPM range
- Switch to 7.400” length pushrods to allow more lift
- Consider switching to a shaft mount roller rocker system
Intake And Headers
- Match with high flow intake manifold like Fast LSXR
- Optimized long tube headers enhance top end breathing
- 92mm drive-by-wire throttle body handles the airflow demands
There are additional advanced tuning techniques that can further optimize LS engines equipped with 862 LS heads – but this covers the basics that will get you 90% of the way there.
Where to Buy 862 LS Cylinder Heads?
Now that you’re familiar with the 862 heads and how to install them, here’s a quick guide on sourcing them for your LS project.
OEM GM Castings
You can still find brand new OEM 862 cylinder heads from some dealers and parts warehouses. However, GM discontinued production so inventory is very limited. Expect to pay over $2500 per pair.
Most builders rely on remanufactured heads which offer comparable quality for less cost. Some reputable 862 reman sources include:
- Texas Speed – Fully remanufactured castings with multiple finish options to choose from
- Summit Racing – Large selection of affordable 862 castings guaranteed to meet OE specs
- BluePrint Engines – Great quality reman LS heads including 862s ready for drop-in install
When buying remans, expect to pay a core charge up front that is refunded once you send your old heads back. This is typically around $500.
Remanufactured 862 heads run $1200-1800 for assembled castings. So with the core charge, plan around $1700-2300 total for a remanned set.
Used LS Heads
You can save money buying used 862 castings from forums, Facebook groups, Craigslist, etc. But inspect carefully to ensure the head decks, seats, guides, and valves are in good shape.
FAQs about 862 LS Cylinder Heads
We’ll wrap up this guide on 862 heads with answers to some frequently asked questions.
Are 862 heads compatible with my LS engine?
The 862 heads work with Gen III and Gen IV LS-family blocks including 4.8L, 5.3L, 6.0L, 6.2L, 7.0L, and custom stroker combos. They are compatible with LSx style intake manifolds.
What changes are needed to run 862 heads?
You’ll need valve springs for at least .600” lift, proper length pushrods, and tuning changes like camshaft profiles to optimize the 862’s flow. No major engine modifications are required.
How much horsepower do 862 heads add?
Typical gains are 60-80 hp over stock cathedral-port LS heads. With supporting mods like cam, intake, and headers – 125 hp gains or more are possible.
Do I need to modify the valvetrain to run 862 heads?
You will need upgraded valve springs rated for at least .650” lift to handle aggressive camshaft profiles that optimize the 862 heads’ airflow. The stock LS valvetrain components are not designed for high lift. Titanium retainers are also recommended.
What intake manifolds work with 862 heads?
The 862 heads have the standard LS-style intake bolt pattern and port openings. Any cathedral or rectangular port LS intake will bolt right up. Popular choices are FAST LSXR, Holley Hi-Ram, Edelbrock Victor Jr, and GM LS3.
What type of headers should I use with 862 castings?
Long-tube headers are ideal to take full advantage of the 862’s high-flow exhaust ports. From 1-3/4” to 2” primaries work well, with 1-7/8” being the sweet spot. Kooks, Hooker, and Schoenfeld make quality LS swap headers.
How difficult is the 862 head swap process?
It’s straightforward if you have access to a machine shop to check for straightness and surface the decks. Use torque plates when machining aluminum heads. The rest is basic LS wrenching – new gaskets, bolts, valves, etc. An experienced mechanic can swap 862s in a weekend.
What kind of power can I expect from 862 heads on a stock LS?
On an otherwise stock 5.3L or 6.0L truck motor, you can conservatively expect 80-100 hp gains with supporting mods. With upgraded cam, intake, and headers – 400-450whp is achievable on pump gas.
Upgrading to a set of 862 heads is one of the most effective ways to unlock substantial horsepower gains from LS engines like the 5.3L and 6.0L. With their excellent flow characteristics, lightweight aluminum construction, and proven power potential, 862 castings are a premier option for both mild and wild LS builds alike.
As we’ve covered, the 862 heads offer significant airflow and compression improvements over stock LS castings. By optimizing your combination with the right camshaft, intake, headers, and tuning, 400-500+ horsepower is readily achievable from these heads.
While the stock LS valvetrain may need upgrades to handle the 862’s flow potential, the swap process itself is straightforward. Quality remanufactured castings provide an affordable option vs brand new OEM heads.
If you’re looking to boost an otherwise stock or mildly modified LS engine well past the 500hp mark, 862 cylinder heads are undoubtedly one of the best bang-for-buck power mods available. Their excellent velocity and high lift flow abilities make them a top choice for both street and racing LS engines.
With this comprehensive guide, you now have all the details on properly selecting, installing, and tuning 862 heads for your LS build. We covered how these castings compare to stock heads, technical design features, top LS engine applications, essential installation steps, tuning tips, where to source them, pricing, and much more.
Hopefully this gives you the confidence to tap into the big power potential of the legendary 862 LS cylinder heads on your next turbocharged, supercharged, or naturally aspirated Gen III/IV LS project!