How It Works: T&D Machine Products Internally Oiled Rocker Arms

Valvetrain parts in any engine need to be properly lubricated. This is especially true in a high-performance application to prevent catastrophic failure. T&D Machine Products uses a unique system to keep its rocker arms lubricated and oil flowing to critical valvetrain parts. In this article, we’re going to take a look at T&D’s internal oiling system for rocker arms and how it works.

Valvetrain Lubrication Explained

Oil’s journey to the valvetrain typically begins at the bottom of the engine, in the oil pan. From there, the oil is picked up and pumped through the engine, where it makes stops at the main and cam bearings. Oil is moved through the block’s oil galleries to the lifters, where it’s then pushed through the center of the hollow pushrods toward the top of the engine (unless it’s a Mopar that oils through the shafts). The oil from the pushrod is sent to the cup at the tail of the rocker arm to lubricate that touchpoint where the rocker arm and pushrod meet.

In most applications, when the oil reaches that cup, that’s where the pressure system ends for the oil. Each rocker arm and valve tip have to rely on oil spray that’s contained inside the valve covers or rocker boxes for lubrication. The hydraulic wedge of oil that fills the space between each surface of the valvetrain parts is generated from this spray, as the oil is moved around under the valve covers.

Rocker arms are a critical part of the combustion process. They make sure gases are entering and exiting the cylinder when an engine is running.

There are custom applications that have been designed for engines that modify how the top of the valvetrain is lubricated. Most engines aren’t going to use these systems due to the cost, or the fact they won’t work with the engine’s architecture. That’s why it becomes so important to make sure you’re using high-quality oil and the right parts to keep the top of your valvetrain adequately lubricated.

Phil Elliott from T&D adds his thoughts on why proper lubrication is so important.

“Adequate lubrication is key to longevity in high-stress areas of internal combustion engines, such as parts that rotate or rock. These include the crankshaft, connecting rods, camshaft, and rocker arms. Without what is called the hydraulic wedge, extreme friction causes things to come to a screeching and literal halt.”

T&D’s Internal Oiling Rocker Arms

Rocker arms are subjected to extreme forces as they open and close the valves during the combustion process. Those forces put a lot of pressure on the moving parts of the rocker arm like the trunnion and roller tip. There needs to be plenty of oil supplied to these areas to prevent damage. T&D’s internal oiling system for rocker arms allows oil that’s constantly pressurized to be fed to the trunnion bearings and rocker arm tips.

The rocker arm oiling puzzle was something that required creative thought and design — T&D looked at how a rocker arm could be modified to be the vessel for the oil, and created its internal oiling system.

T&D's adjuster is the backbone of the internally-oiled rocker arm. The two small orifices in each adjuster are what feeds the rocker arm its oil.

“Unlike a standard pushrod cup, a T&D adjuster has a precision 0.060-inch hole machined into its center. This meets another 0.060-inch hole drilled perpendicular to the main hole. On the outside of each adjuster, among the threads, is a machined channel that retains a ring of oil,” Elliott explains.

The adjuster plays an important role in how the internal oiling rocker arms work. If the adjuster is set up or down from the correct position, it won’t allow oil to flow through the rocker body as intended. – Phil Elliott, T&D Performance Products

Elliott goes into further detail about the rocker arm’s internal oiling system.

“It was determined that precision-drilled holes needed to go through the rocker body itself. The holes in the adjuster meet up with those in the rocker body. The proper placement of those orifices is why adjuster placement and lash settings with T&D rockers are so critical. Too high or too low in the rocker will effectively stop the flow. They must line up properly to prevent the oil flow from being cut off. The oil flows through the hollow pushrod, right through the adjuster, to be sent through the channels in each rocker to lubricate the trunnion bearing and the roller tip.”

This diagram shows how the oil travels through the rocker arm.

The T&D rocker arms use the engine’s oil pressure to assist with the self-lubrication process. High-performance engines are going to see elevated oil pressure levels. According to Sheldon Miller from T&D, the internal oil system for its rocker arms are more than capable of dealing with the oil pressure.

“In the vast majority of race engines, the builders will restrict oil to the top end. Way back in the day that was okay. But now, with increased loads, we like seeing as much oil to the top end as possible. We don’t like seeing restrictors having anything less than a .090-inch orifice so that adequate oil can be supplied. There are some forms of racing that will literally fill the valve cover with oil and use a dry sump pump to pull the oil out of the valve cover area. Those guys found the advantages of oil supply to the rockers and springs life.”

The internally oiled rocker arms that T&D produces aren’t made with any crazy space-age techniques — they are made in a way that they retain as much stiffness as possible so they can deal with the aggressive camshaft designs that are used in high-performance engines. The level of stiffness that T&D incorporates into its rocker arms doesn’t impact their geometry — this means the rocker arms will perform at a high level, while still taking advantage of the oiling system.

Proper lubrication is what allows a rocker arm to do its job even under the most extreme conditions.

If you’re going to build an engine that will be pushed hard, the right valvetrain parts are an important part of the engine package. Rocker arms that are internally oiled will provide you with several advantages that will improve the engine’s performance and longevity.

“We feel that having pressurized engine oil supplied to the bearing is an advantage for longevity. It’s rare to see bearing issues with our product because we have actual engine oil pressure at the bearing. If we do have a customer that has an issue, after chatting with them, it typically comes down to either the quantity or quality of oil supplied to the rocker that is the issue. Once the rocker gets enough oil, and the quality of the oil is good, the issues go away,” Miller says.

T&D Machine Products has found a way to extend the life and performance of its rocker arms thanks to an internal oiling system. These rocker arms are designed to reduce the stress and wear that rocker arms are exposed to in a high-performance engine.

Article Sources

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. When Brian is not writing, you can find him at the track as a crew chief, doing freelance photography, or beating on his nitrous-fed 2000 Trans Am.
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