You’ve seen “DOHC” on an engine spec sheet or heard it mentioned at a parts counter—but if you’ve never really looked into how engines are built, it probably sounds like alphabet soup. Spoiler: it’s actually pretty straightforward, and once you get it, you’ll start to see why so many modern engines rely on this setup.
DOHC stands for Dual Overhead Camshaft (though some people might call it a “double overhead camshaft”). And yes, that’s a mouthful. But all it means is that the engine has two camshafts sitting on top of the cylinder head—one that opens the intake valves, and another that works the exhaust valves. That direct control over the intake and exhaust valves gives the engine more precise breathing, which translates to cleaner combustion and more usable power.
This isn’t a brand-new concept. Overhead camshaft engines have been around since the early 1900s, but they didn’t really go mainstream until the 1960s. Why then? Because automakers needed more from less—engines that could meet rising efficiency demands, run cleaner, and still hold their own on the highway. Jalopnik breaks it down well.
What Makes DOHC Different?
Here’s where we zoom out. In older pushrod engines, the camshaft is buried in the cylinder block, pushing rods and rockers to open the valves. It’s simple and rugged—but not exactly known for surgical precision.
With dual overhead cams (sometimes called double overhead cams), you skip all that extra hardware. The cams are right above the valves. Fewer moving parts in the valvetrain, tighter control, and way better timing.
Also, DOHC engines typically run four valves per cylinder—two for intake, two for exhaust. That lets more air and fuel mixture in and more burned gas out. More airflow = more power. You’re getting more out of the same engine displacement, which is a win.
What’s the Real Advantage?
One word: flexibility. Most DOHC engines include variable valve timing, meaning the ECU can tweak exactly when the exhaust valve opens or when the intake closes—depending on RPM, load, or even ambient temperature. That gives you strong torque at low RPM, better fuel efficiency at cruise, and solid top-end power when you really lean on it.
And if you’re tuning or building? A DOHC setup gives you more wiggle room. You can adjust valve lift, get aggressive with your camshaft profiles, or chase emissions targets without giving up drivability.
What About the Downsides?
Sure—nothing’s perfect. DOHC layouts are more complex than a single overhead camshaft setup. There are more parts, more precision machining, and they tend to take up more space. That’s not ideal in a tight engine bay, or if you’re on a budget.
But for modern engines, especially turbo diesels or anything that sees hard use, the performance and durability benefits far outweigh the added complexity. Once you’ve seen the difference in how they breathe, it’s hard to go back.
DOHC vs. SOHC: Which One Wins?
It’s not really a “better or worse” situation—it’s about matching the tool to the job. A SOHC (Single Overhead Camshaft) engine is easier to service, has fewer parts, and can work great in commuter cars or light-duty rigs.
But if you’re building for torque, tuning for high RPM, or just want something that can handle more aggressive timing without flinching? Dual camshafts are going to give you more options.
Why Behind The 8 Is Your Go-To for DOHC Engine Parts
At Behind The 8, we don’t just talk about this stuff—we live it. Whether it’s DOHC camshafts, high-quality cylinder heads, or the bits and pieces that hold them together, we only stock what we’d use in our own builds.
Not sure what you need? Get a quote. We’ll help you sort out the right parts for your engine, no fluff, no guesswork—just real advice from people who get it.
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