Pushrods are thin metal rods inside an engine that transfer motion from the camshaft, located deep in the engine block, up to the rocker arms and valves at the top of the cylinder head. They’re the messenger in a relay system: the camshaft spins, pushes a lifter upward, the lifter pushes the pushrod, and the pushrod tips a rocker arm that opens a valve to let air and fuel in or exhaust out. This design is called an overhead valve (OHV) engine, and it’s been a staple of American engine building since Chevrolet introduced its small-block V8 in 1955.
How the Valvetrain Works
The process starts at the camshaft, a rotating shaft with egg-shaped lobes machined along its length. As the camshaft spins, each lobe pushes against a small cylindrical component called a lifter (or tappet). The lifter rides on top of the lobe, and when the lobe’s high point comes around, it forces the lifter upward. The pushrod sits on top of the lifter and moves upward with it.
At the top end, the pushrod presses against the underside of a rocker arm. The rocker arm works like a seesaw: when the pushrod pushes one side up, the other side pivots downward and compresses a valve spring, opening the valve. When the camshaft lobe rotates past its high point, the spring pushes everything back into place and the valve closes. This cycle happens thousands of times per minute at highway speeds.
Pushrod Engines vs. Overhead Cam Engines
The main alternative to a pushrod engine is an overhead cam (OHC) design, where the camshaft sits directly above the valves in the cylinder head. This eliminates the need for pushrods entirely. The camshaft lobes press on the valves more directly, reducing the number of moving parts between the cam and the valve.
That difference in layout creates real tradeoffs:
- Size and weight: Pushrod engines are more compact because the camshaft is tucked inside the block rather than mounted in the head. This makes them easier to fit into tight engine bays, which is one reason they’ve remained popular in American trucks and sports cars.
- Low-end torque vs. high-RPM power: Pushrod engines typically produce strong torque at lower RPMs, making them well suited for towing and acceleration from a stop. OHC engines can rev higher, often past 7,000 RPM compared to the pushrod ceiling of roughly 6,500 RPM, which lets them produce more peak horsepower.
- Maintenance cost: Pushrod engines are mechanically simpler, which generally means cheaper repairs. Many OHC engines use timing belts that need periodic replacement, while pushrod engines typically use timing chains or gear drives that last longer.
- Technology: OHC designs more easily integrate modern features like variable valve timing, which improves both fuel economy and emissions. Pushrod engines have more limited options on that front.
Why Pushrod Engines Have an RPM Ceiling
The pushrod, lifter, and rocker arm all have to change direction rapidly as the engine spins faster. That’s a lot of mass accelerating and decelerating thousands of times per minute. As RPMs climb, the springs controlling this system struggle to keep every component in contact with the next. Engineer Jason Fenske, known for his technical breakdowns of engine design, explains that the reciprocating mass can “outrun the spring,” causing parts to briefly lose contact. At that point, valve movement no longer tracks the camshaft accurately. This is called valve float, and it’s the practical limit on how fast a pushrod engine can spin.
Overhead cam engines sidestep this problem by eliminating the pushrod from the equation. Many also use four smaller valves per cylinder instead of two larger ones, with lighter springs for each. Less mass moving back and forth means more precise valve control at high RPMs.
What Pushrods Are Made Of
Three materials dominate pushrod construction. Standard steel pushrods come in most factory engines. They’re cheap and adequate for stock power levels, but they’re relatively heavy and not especially strong under high loads. Chromoly steel (a chromium-molybdenum alloy) is the go-to upgrade for performance engines. Chromoly pushrods are lighter and stronger than plain steel, which reduces valvetrain mass and improves durability when engines are making more power than stock. Aluminum pushrods are the lightest option and show up primarily in racing, where shaving every possible gram of reciprocating weight matters. The tradeoff is reduced long-term durability, which is acceptable when engines are rebuilt between races but impractical for daily driving.
Why Pushrod Length Matters
Getting pushrod length right is one of the more critical measurements in building or rebuilding an OHV engine. If a pushrod is too short, the rocker arm can’t open the valve fully, and you end up with sloppy clearances that hurt performance and create noise. If it’s too long, the valve spring can bind at full compression, which leads to rapid and expensive valvetrain damage. A pushrod that’s too long can also prevent the valve from closing completely, which causes compression loss and potential engine damage.
In a stock engine with factory parts, pushrod length is predetermined and rarely a concern. But any time you change components like the camshaft, cylinder heads, or rocker arms, every pushrod location needs to be measured individually. The goal is a length that provides zero clearance (called zero lash) between the lifter, pushrod, and rocker arm when the valve is fully closed.
Hydraulic Lifters and Valve Adjustment
Most modern pushrod engines use hydraulic lifters, which automatically compensate for small changes in clearance as the engine heats up and parts expand. These lifters use oil pressure to maintain the right amount of contact between the pushrod and rocker arm, so manual valve adjustments are rarely needed during normal ownership. Engines with solid (non-hydraulic) lifters, common in older cars and some racing applications, require periodic manual adjustment to maintain proper clearance.
When hydraulic lifters are installed or replaced, the pushrod is typically set to zero lash and then extended slightly to preload the lifter. The lifter then needs time to “bleed down,” meaning the internal hydraulic piston settles into its operating position. This process takes 20 to 30 minutes per lifter and is one of the more time-consuming parts of a valvetrain assembly.
Where Pushrod Engines Are Still Used
Despite being an older design concept, pushrod engines remain widespread in 2025, particularly in full-size trucks and performance cars. The Chevrolet Silverado and GMC Sierra use 5.3-liter and 6.2-liter pushrod V8s. Ford’s Super Duty trucks offer 6.8-liter and 7.3-liter pushrod V8s. Ram’s heavy-duty trucks use a 6.4-liter pushrod Hemi V8, and the 2026 Ram 1500 brings the Hemi back as well. Ram also pairs with Cummins for a 6.7-liter pushrod inline-six diesel.
On the performance side, the 2026 Chevrolet Corvette still comes standard with a 495-horsepower pushrod V8. The combination of compact dimensions, strong low-end torque, proven reliability, and relatively simple maintenance keeps the pushrod architecture relevant for applications where peak RPM matters less than the broad, usable power band these engines deliver.