Automotive Performance & Tuning Guides

Chevy LS3 Camshaft Upgrade Guide

When it comes to Chevy small blocks, chances are you want to get the most power out of them. They are some of the easiest engines to modify and you don’t have to spend a fortune on parts and labor. The Chevrolet 6.2L LS3 crate motor is one of the most popular models offered by GM. The LS3 is one of the most common swap options beyond the C5 Corvette and Gen 5 Camaros. There is no doubt an LS swap has crossed your mind if you’re aiming for high horsepower.
Despite the Chevy LS3’s impressive 430 horsepower and 428 pound-feet of torque, it offers so much more fun. This is where an upgraded LS3 camshaft comes in. Stock LS3 cams are not a bad choice if a smooth idle and moderate power are important to you. As a result, a more aggressive cam can do more than just liven up your LS3 engine.
There is no shortage of options available when it comes to upgraded LS3 cams. LS engines benefit greatly from aggressive camshafts, so there is a very thriving aftermarket LS camshaft scene. Even though massive cams are available for the LS3, that doesn’t necessarily mean they’re the best option. The performance characteristics of an upgraded LS3 camshaft must be considered before throwing in the biggest one you can find. That’s exactly what we’ll cover in this guide. Here are some of the most popular LS3 camshaft choices and how they affect performance.

Chevy 6.2L LS3 Camshaft Upgrade Considerations

Compared to other modifications that would yield the same power gains, an LS cam upgrade is a piece of cake. The upgrades are not directly plug-and-play. In addition to replacing other supporting hardware, other considerations must be taken into account. Stiffer LS3 valve springs are the most significant supporting upgrade. Besides locks, retainers, seals, and seats, improved locks, retainers, seals, and seats should also be considered.

Upgraded LS3 Valve Springs

Adding stiffer valve springs to a 6.2L LS3 is a requirement when swapping a more aggressive camshaft. There is a relatively simple reason for that. The factory valve springs in the LS3 were designed to handle the relatively mild stock cam. Consequently, the stock valve springs cannot keep up with the larger lobes of an upgraded cam.

Multiple potential problems could arise if you swapped in an upgraded LS3 cam without also upgrading the LS3 valve springs. The increased RPM potential of an aggressive LS3 cam can cause the engine speed to surpass the valve spring’s capabilities. Floating valves can result in less-than-ideal performance.

An upgraded LS3 cam also increases lift values, which can present another potential issue. Factory LS3 springs are generally capable of handling lifts between 0.500 and 0.525. The performance of a lot of LS3 performance cams will surpass that figure. It is possible to damage your valvetrain by coil bind if you run an LS3 camshaft with lift above the stock amount.

LS3 valve float and coil bind can be serious problems, but there is a very simple solution. Whenever you replace your camshaft, make sure you also replace your valve springs. In the same way that LS3 cams come in all shapes, sizes, and rates, upgraded LS3 valve springs do as well. The LS3 valve springs should be able to withstand the extra force applied by the cam without being overly stiff. Power can be zapped by stiff LS3 valve springs.

6.2L LS3 Piston to Valve Clearance

Additionally, piston-valve clearance should also be considered when upgrading LS3 cams. By upgrading the camshaft in your LS3, you are also decreasing the distance between the valve head and the piston. The duration and lift of the LS3 cam you choose are very important here. The intake side clearance should be between 0.08 and 0.100 inches, and the exhaust side clearance should be between 0.100 and 0.120 inches. When it comes to LS3 PTV clearance, it is far better to err on the side of caution rather than risk having valves smashed.

For LS3 piston-to-valve clearance issues, there are a couple of solutions. The most common solution is to fly cut your LS3 pistons. Fly cutting involves replacing the LS3 valves with a notching tool. The head is then reinstalled with the tool in place. Electric drills can be used to spin the cutting tool, which creates a cut in the piston head. The steps above are obviously a simplified version of what it takes to properly fly cut an LS3 piston.

There are relatively few steps involved in fly cutting. To determine how much material needs to be removed from the piston head, you must consider your cam lobe and valvetrain geometry. The milled heads and gaskets you choose to run also contribute significantly to fly cut depth. Don’t forget to take them into account.

LS3 Pistons with Reliefs

LS3 pistons can be purchased with reliefs already cut into them if you’re not interested in doing the DIY work. There is no shortage of LS3 pistons with intake and exhaust valve reliefs, as there is with most LS3 engine components. An LS3 piston set with JE pistons is one of the most popular options for high-horsepower applications. As well as having massive valve reliefs, they are also forged, which means they will fit almost any cam.

Tuning LS3 Upgraded Cam

LS3 camshafts must be tuned together with the PCM after installation. You must make sure that your LS3 PCM recognizes the changes in cam timing. A modified LS3 cam adjusts valve lift and duration, so the onboard computer needs to adjust for the increased airflow. You’ll run into fueling issues without a tune. Additionally, you’ll need to adjust your 6.2L V8’s idle as well. As a result, the engine will surge and idle out due to the altered cam timing.

Untuned PCMs do not know that your new cam’s overlap period is allowing some idle airflow (and fuel) to escape. LS3 cam upgrades require a tune for all of those reasons.

Choosing the Right LS3 Camshaft

There are many camshaft options available for the LS3, making it difficult to choose. In addition to these considerations, you should also start thinking about how you want your 6.2L LS3 to behave. Engine performance can be dramatically improved by swapping LS3 cams. The cost of high power figures is usually the loss of daily drivability. More aggressively tuned LS3 cams will make your car less streetable.

The most important thing to consider before choosing a cam is what you plan on putting the engine through. Over-camming an LS3 is the worst thing you can do if you aren’t building a track car. When choosing a cam, it’s easy to be convinced that max power is best, but that’s not always the case.

LS3 204/211 .551/.525 117 camshafts clearly find a middle ground between performance and streetability. In addition to providing a smooth idle, the stock cam also provides a high level of fuel economy. Those are also two sacrifices that come with an aggressive cam.

In general, the wilder the cam profile, the less performance you’ll get at low speeds. A direct tradeoff is made between low-end performance and high-end power. In spite of this, there is a solid middle ground that can improve performance throughout the entire rev range.

For the purposes of this guide, we’ll focus primarily on cams for naturally aspirated LS3 engines. As a result, cams designed for LS3s running forced induction have different characteristics from those designed for N/A engines.

Common LS3 Cam Profiles

Let’s briefly discuss what the numbers associated with camshaft specifications mean before diving into some of the most common LS camshaft profiles. There will be a complete cam card breakdown in the near future, which will provide even more detailed information about cam specifications. As a starting point, let’s cover the basics.

Airflow can be increased in three ways with upgraded LS camshafts. In addition to valve lift and valve duration, valve event timing is also considered. There is a consistent format for listing cam specifications across all manufacturers.

A factory LS3 camshaft, for example, has 204/211 .551/.525 117 specifications. For the intake and exhaust valves, the first designation (204/211) represents valve lift. An intake valve’s lift is how far it opens, as well as an exhaust valve’s lift. In general, the longer the valve is opened, the more power is produced. You put more strain on the LS valvetrain as the lift increases.

In the second group of figures (0.551/0.525), the valve duration is represented. During the valve duration, the valve is open for a specific amount of time. By increasing the duration of a cam lobe, you give cylinders more time to fill with fuel and air. As a result, the valvetrain wears out more quickly, resulting in more power.

Figure 117 represents the lobe separation angle, which is directly correlated with valve event timing. A motor’s intake/exhaust valve opening and closing points have a significant impact on total airflow of a cam profile, as well as the RPM range at which a motor is most efficient. Profiles with LSA characteristics that emphasize high-RPM airflow will sacrifice low-RPM performance. Inversely, this is also true.

Let’s discuss some of the most common LS3 cams now that we’ve covered some of the basics.

LS3 Camshaft Upgrade Summary

There are many benefits to upgrading your LS camshaft. The stock cam in the LS3 is really the limiting factor due to its highly optimized factory heads and intake. Due to the fact that LS camshafts are such an effective modification, there are a lot of them available. Before upgrading an LS camshaft, there are a few key considerations to take into account.

The installation of an extremely aggressive LS3 camshaft has a few limitations. Firstly, the factory valve springs aren’t designed to handle the forces produced by an upgraded LS camshaft. The second problem is piston to valve clearance, which can be solved with fly-cut pistons or valve reliefs.

After considering these factors, you’ll need to determine which LS camshaft is right for you. The bigger the better doesn’t always mean the better. A LS-powered car should not be driven on a daily basis, especially if you plan to drive it every day. LS cams with high-RPM performance often sacrifice low-RPM performance, which decreases drivability. It is highly specialized to each individual setup of your engine since an upgraded LS camshaft works in conjunction with various engine components. It is also necessary to reflect that in your respective LS cam tune. GM performance shops are a great resource if you’re having trouble picking the right cam for your LS3 project. Don’t waste your time and money on a cam that may not suit your needs. Make sure you consult a professional to guarantee your satisfaction.

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