If you want to take your diesel engine to the next level, there are plenty of options out there. Massive compound turbos, 250% over injectors, and dual CP3 kits can be found under the hood of race trucks across the country.

Those parts are the basic ingredients that will give your engine the fuel and airflow to create massive horsepower. But just as important as the big air and fuel delivery upgrades, are a lot of small parts that go inside your engine that should be upgraded along the way to help support the horsepower your bullet is capable of making.

All modern diesel engines are four strokes, which requires valves to operate properly. They allow air needed for combustion into the engine, and spent exhaust gasses out. Inside the block, there is a camshaft which controls when the valves open, how far they open, and how long they stay open. And if the valves don’t open or close when they are supposed to, your engine can drop power, and in a worst-case scenario, cause severe mechanical damage from parts touching when they shouldn’t. A valve spring’s job is to close the valve, and to do so, needs to have enough force to overcome the pressure in the intake or exhaust manifold pushing against the valve. But the spring also has to move several other parts along the way. 

There is a tremendous amount of mass (in engine terms) in a diesel’s valvetrain. Each pair of springs in a 4-valve diesel is responsible to move a rocker bridge, rocker arm, pushrod, and lifter back down onto the cams base circle, and this all has to occur thousands of times per minute. The factory designed the stock spring to operate at a certain RPM range and boost pressure, which is very easy to exceed. There are two ways you can run into trouble. One is spinning the engine too fast: When the RPM increases beyond the factory threshold, the stock valvesprings can’t close the valve and push the mass of the entire valvetrain back down onto the closing cam lobe quick enough. This is known as valve float. The second way is from pressure: higher boost or exhaust drive pressure is working against the valvespring; pushing against the backside of the valve, trying to force it open.

Upgrading the valvetrain isn’t for the faint of heart. The job is easiest on the Cummins engines, as there is the least amount of stuff you need to remove in order to gain access, but it is still a job the average shade tree mechanic might not want to tackle. Once the valve cover, wiring harness, and injectors are out of the way, the rocker arms and valve bridges must come off. Then, a specialized tool is required to compress the springs and allow the keepers to be removed, and the engine has to be rotated to top dead center on each cylinder to ensure the valves don’t drop into the combustion chamber. Finally, once the new springs are installed with the tool, the tiny keepers have to carefully be installed without dropping them into the engine, and valve lash has to be precisely set.

And the camshaft? Well, that’s a deep dive into the center of the block, requiring many hours of labor. They say nothing in life worth having comes easy, and a high-performance diesel is no different. If the intake, programmer, and exhaust on your truck just aren’t cutting it anymore, crack open the engine, sprinkle in a few parts, and get ready to pump out some power. Just don’t forget to support the valvetrain along the way.