Needle Bearings Versus Trunnion Bushings with the Chevy LS

Bronze and beautiful: Steve Morris Engines’ trunnion bushing kit.

Despite Chevrolet’s LS line of aluminum V8s being robust, capable, and generally well-designed motors, they’re not without the odd mechanical gremlin. In the case of the LS, the factory needle bearings are a failure-prone component. Though the factory rocker arms are light and have a low moment of inertia, their needle bearing rollers are known to fall into the engine, even under normal operation. In recent years, some aftermarket manufacturers have devised caged needle bearings to try and retain the rollers in the event of them falling out, collecting in the oil pan, and often damaging the engine.

Some others, like Steve Morris Engines, have moved in a slightly different direction. Using a solid bronze bushing with machined oil channels at the eleven and one o’clock positions of the trunnion’s pivot, they’ve devised a way to ensure reliability in high-performance applications. We’ve been fortunate enough to ask Alex Esnaola, Business Manager at Steve Morris Engines, why these bushings are the definite step forward for an enthusiast with greater reliability in mind.

Are there any advantages trunnion bushings hold in the reliability department?

Alex Esnaola: Yes, from the standpoint that the load is better distributed across a broader piece of metal. The trunnion bushings will carry three-hundred times more load thanks to much more contact area than with the standard needle bearings.

We see plenty of people trying to get away with stiffer springs or more aggressive cams used in conjunction with the factory rocker arms, which simply aren’t up to the task when revving very high. In our opinion, the factory rocker arm is good up to 7,500 rpm, but even there you’re flirting with danger. While our trunnion bushings won’t allow for higher revs, they’re a precautionary upgrade – they improve reliability at the upper end of the stock rev range. For endurance racing, this is a must.

It should be said that even under normal operations, factory needle rollers can fall out. It’s freaky seeing metal fragments in the oil during an oil change, especially since it happens so often.

With both the trunnion bushings and the needle bearings, what happens in the event of a failure?

Esnaola: All that really happens with a trunnion bushing wearing out is that the rocker loses lash and gets loud. For one to actually fail, you would have to snap a trunnion or burn through a bushing – and I haven’t seen either of those happen yet.

There is also a side benefit that there is no chance of any loose needle bearings destroying the engine when using much more aggressive camshaft profiles and severe duty valve springs if a factory rocker bearing fails.

With machined oil channels at the eleven and one o’clock positions of the trunnion’s pivot, these bushings provide better lubrication despite having greater rolling resistance.

How do the two differ in terms of lubrication issues?

Esnaola: Well, needle bearings have less rolling resistance. However, at the revs our bushings are typically subjected to, there’s no major frictional disadvantage. In fact, the machined channels constantly feed oil to the bushing surface and trunnion, ensuring proper lubrication, which is unlike needle bearing trunnions that have to rely on oil searching its way into the needles.

Some people talk about oil coking around needle bearings or bushings, but in reality, the engine has to be beaten like it owes you money to see this. If that coking is happening, it’s a symptom of an unhealthy motor, and there are bigger problems afoot.

With our bushing kit, converting from needle bearings to trunnion bushings requires no change in oil – it’s an incredibly simple conversion process.

On that note, if someone wants to move from needle bearings to trunnion bushings, what does the conversion process entail? Do you offer different packages for the those who are a little less comfortable with wrenching?

Esnaola: We offer two options. If you prefer to do it yourself, we offer a DIY kit with detailed instructions, and it doesn’t require tons of mechanical expertise. We can also take your rocker arms and upgrade them ourselves. We’ll run them through an ultrasonic tank to clean them, refresh them if necessary, and press in the trunnion bushings. 

Adding the trunnion bushings can be done either with a DIY kit, or by having Steve Morris Engines clean, refresh, and retrofit your factory rocker arm.

Finally, who is best benefited by using your bushing kit?

Esnaola: We’ve designed this kit primarily to ensure peace of mind. While it won’t allow for a gain in revs, it offers a more reliable platform to build upon. Whether you’re going for a bone-stock rebuild, adding a more aggressive cam, or chucking on some severe duty valve springs, this kit will ensure more mileage out of your motor.

The kit includes the modified trunnion, bronze bushings, and C-Clips, and can be used with the stock or ARP rocker arm bolts. As these trunnion bushings fit all OEM LS cast rockers, including those found in the LS1, LS2, LS3, LS6, and LS7, they suit just about any application in modern, performance-oriented Chevrolets, and ensure the reliability needed in a motor that gets pushed regularly. 

Again, the trunnion bushing does not allow for a raise in the rev limit, but offers the promise of a stronger platform when modifying. Whether you’re just looking to refresh your stock LS, make minor tweaks to the head, or completely overhaul your engine motor in the future, this is one modification that directly addresses one of the few flaws in Chevrolet’s original design. For absolute serenity when hustling your Camaro, GTO, or Corvette on the drag strip or through the road course, there are few upgrades more suited to the task.

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About the author

Tommy Parry

Tommy Parry has been racing and writing about racing cars for the past seven years. As an automotive enthusiast from a young age, he worked jobs revolving around cars throughout high school, and tried his hand on the race track on his 20th birthday. After winning his first outdoor kart race, Tommy began working as an apprentice mechanic to amateur racers in the Bay Area to sharpen his mechanical understanding. He has worked as a track day instructor and automotive writer since 2012, and continues to race karts, formula cars, sedans, and rally cars in the San Francisco region.
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