Properly Planning A Turbocharged LS Valvetrain

Project Swedish Meatball’s boosted LS engine uses an array of off-the-shelf parts, including the entire valvetrain. You don’t need custom parts to build a rock-solid valvetrain, you just need a little bit of knowledge to select the right parts. Nick Evdos, Lead Engien And Induction Tech Support Specialist from Brian Tooley Racing (BTR) spec’d our engine’s valvetrain. He sat down with us to share his knowledge on how to build a turbocharged LS valvetrain, and provided some bonus knowledge on intake selection.

There’s plenty of information on the internet about selecting parts for a boosted application’s valvetrain, but not all of it is correct. One of the key points that Evdos wants to get across is that when you’re working with a company to select parts, you need to be very realistic about your goals, and let them know what parts you’re working with. Things like what cylinder heads you’re using, the max RPM level you’re shooting for, the horsepower goal, and much more is needed to select the right valvetrain parts.

Bigger isn’t always better when it comes to cams for a turbo application…

Camshaft Selection

The main component people think of when you mention an engine’s valvetrain is the camshaft. Out of all the valvetrain parts, the cam dictates how the engine will perform based on your application. RPM, boost level, and how the vehicle will be driven all play into the cam selection.

“The key to getting the right turbo cam is you need to be realistic and truthful about how you’re going to use the engine. If you go too big or small, the cam is just not going to work with the engine. I always tell customers that if it’s a true driver and just something you are looking to have occasional fun with at the track it’s better to err on the small side for the cam. It will run better off-boost You’ll have better torque when it’s not in boost, the engine can build boost easier, and you can run a tighter converter so you don’t put a lot of heat in the transmission,” Evdos says.

You need to select a camshaft that fits your horsepower goals. The cam also needs to complement the other parts of your turbo build.

Evdos and the team at BTR have spent a lot of time behind the controls of a Spintron machine looking at how a cam impacts an engine’s ability to make horsepower. What they have learned is that aggressive isn’t always better for a cam, especially for power-adder applications like turbochargers. It’s all about striking a balance based on the engine, and keeping all the valvetrain parts happy.

“We’ve learned that even if there’s a small power gain in being more aggressive with a cam profile it might not be worth it. You don’t want to sacrifice reliability and valvetrain stability in the name of an aggressive cam. It might be better to keep the cam profile reasonable, and be able to turn the boost up to gain more power. So, it doesn’t make sense stressing the valvetrain out searching for small power gains with the cam in a boosted application,” Evdos explains.

Camshaft selection doesn’t have to be hard, you just need to have a good idea of what your engine build goals are. As Evdos pointed out, the biggest cam isn’t always going to be the best cam for any given application. The more information you have ready, the easier it will be for a cam company to assist you with picking the best camshaft for your specific application.

OEM LS rocker arms are actually really strong and work well in high-performance applications.

Rocking Out With Rocker Arms

LS engines were blessed with a fairly robust rocker arm design from the factory. What that means is the majority of engines that are built for street/strip you don’t need an exotic aftermarket rocker arm. There are a few basic fixes you can make to an OEM rocker, or you can go with an OEM-style rocker that’s had some revisions made to it and still be able to make plenty of horsepower.

“There’s no reason to go to an aftermarket rocker with a hydraulic setup unless you’re breaking rocker arms. The amount of people I have seen run into that issue is minimal, and there’s usually a reason for it other than the rocker arm itself. For the majority of builds, we suggest you use an OEM rocker with an upgraded trunnion kit,” Evdos says.

So, let’s dig a little bit deeper, why don’t you need an aftermarket rocker arm for most turbo LS builds? It all comes down to the enemy of any valvetrain, weight. When you start adding weight to the rocker arm, you have to start adding weight to other parts of the valvetrain, and that can create problems for your standard street/strip application.

Aftermarket rocker arms can actually be a problem for many street/strip turbo LS builds.

“What happens is when you put an aftermarket rocker arm on you’ll want to run a heavier rate valve spring, and that leads to pushrod deflection. Well, then people will move to a bigger pushrod, but now the lifters have to deal with the extra weight and inertia so they’re not happy” Evdos says.

Adding weight to the valvetrain is never a good thing. As you start applying band-aids on top of band-aids, you only compound the issues by adding more weight to the valvetrain.

What Evdos recommends is using an OEM-style rocker arm that has been refined by a company like BTR.

“Our rocker arms address the few issues there are with the factory units. These rocker arms have improved bearing areas and oil channels to make them pretty much bulletproof. All of these changes were made based on what we saw when testing products on the Spintron.”

Just like with camshafts, bigger isn’t always better when it comes to rocker arms. Aftermarket rocker arms can be overkill and might even be more of a problem rather than a solution.

You don’t need fancy lifters for every turbo LS engine build.

Lifter Love

Hydraulic lifters have come a long way. There are hydraulic roller camshaft LS engines running deep into the four-second zone, and Kenny Dangler has run a 3.97 with a hydraulic roller engine. Granted, Dangler’s setup uses a Johnson .903-inch bodied hydraulic link-bar lifter, but that doesn’t mean you can’t get big performance out of an OEM-style lifter. In fact, OEM lifters are perfectly fine for sub-7,200-rpm boosted engines.

You’d be surprised to learn for your average street/strip turbo LS engine it’s not the lifter that makes the difference, it’s actually the lifter tray that’s what will help prevent lifter issues.

“You really need to use a factory GM lifter tray on a standard street/strip LS engine. If it’s not from GM you’re going to have problems. The tolerances are off with those other trays and the lifters move around. As the lifters rock back and forth, the edge of the wheel scrapes across the cam lobe. When that starts to happen, you’re going to experience valvetrain failure at some point,” Evdos says.

The lifter trays are actually the most important part of lifter selection for a turbo LS engine.

The OEM lifters are going to work great for an engine that doesn’t see more than 7,200 rpm when boost is added. You can increase longevity and performance by setting your preload correctly.

“You want to make sure the preload is correct for the OEM lifters. We recommend setting it to .090-inch and that will get most applications in the ballpark where they need to be. Now, if you’re running an aggressive cam or heavy valvetrain parts, the preload will need to be adjusted based on your specific application,”  Evdos explains.

The right valve springs will help your turbo LS engine live a lot longer.

Valve Springs That Spring Into Action

The OEM valve springs on LS cylinder heads aren’t designed for lots of boost or RPM. Valve springs aren’t something you want to try and save money on; you need to get the right springs for your application. A valve spring failure can lead to a broken engine and a very expensive repair bill.

There are all kinds of different valve spring configurations out there, but Evdos recommends you avoid single-spring valve springs for turbo applications. One of the reasons for this is the single springs don’t provide enough valve control. A bigger reason is that if the spring breaks it can’t hold the valve up. This is why Evdos recommends using dual springs, because if there’s a failure it will only be one of the springs. That means there’s another spring keeping the valve from stealing a kiss from the piston and doing some serious damage.

Double springs are the way to go.

Selecting the right valve springs is fairly simple these days because of the cam packages that have been created by cam manufacturers. These packages match components up to ensure the springs can handle the cam you’ve selected. This helps to reduce valvetrain failures and improves performance.

“Most of these turbo LS engines you see on the street don’t need exotic springs. The cam packages that are out there really have got the springs figured out for these applications. It saves people from buying springs that are overkill, or aren’t strong enough for the valvetrain package. ” Evdos says.

If you want to optimize the performance of your boosted LS engine it’s important to use the right valvetrain parts. The parts you select need to not only work together, they need to match your horsepower goals. You can learn more about building a boosted LS engine with RPM Engine and Machine right here. You can also see what Big 3 Racing and Summit Racing Equipment filled our engine with right here.


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About the author

Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. Brian enjoys anything loud, fast, and fun.
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