How Many Camshafts Does an Inline DOHC Engine Have?

Two. In an inline engine with a double overhead camshaft (DOHC) layout, there is a single cylinder head and DOHC places two camshafts in that head—typically one dedicated to the intake valves and one to the exhaust—so the total is two camshafts. By comparison, DOHC V or flat/boxer engines have two camshafts per cylinder head, usually totaling four.

What “DOHC” Means

DOHC stands for double overhead camshaft. It describes an overhead-cam valvetrain that uses two separate camshafts mounted above the cylinders: one to actuate intake valves and another for exhaust valves. This separation improves breathing, enables multivalve designs (commonly four valves per cylinder), and facilitates independent variable valve timing on intake and exhaust cams for better power, efficiency, and emissions control.

Inline vs. V/Flat Engines: Camshaft Counts by Layout

Engine architecture determines how many camshafts a DOHC design requires overall, because camshafts are installed per cylinder head. The following outlines common layouts and their typical camshaft counts.

• Inline DOHC (e.g., inline-4, inline-6): 2 camshafts total (one intake, one exhaust in the single head)
• V6/V8 DOHC: 4 camshafts total (two per head across two heads)
• Flat/boxer DOHC (e.g., some Subaru and Porsche engines): 4 camshafts total (two per head across two heads)
• Inline SOHC: 1 camshaft total (single overhead cam operating both intake and exhaust via rockers or followers)
• OHV/pushrod (cam-in-block): 1 camshaft in the block operating all valves via lifters, pushrods, and rockers

Because inline engines have just one cylinder head, the DOHC format results in two camshafts overall, while multi-bank engines effectively double that count.

Why Inline DOHC Engines Use Two Camshafts

Beyond simply meeting the definition, using two camshafts in an inline DOHC engine offers tangible performance and efficiency advantages.

• Independent control of intake and exhaust timing enables flexible variable valve timing and broader powerbands.
• Improved airflow from optimized valve events and angles supports higher specific output and better high-rpm breathing.
• Multivalve compatibility (often four valves per cylinder) enhances combustion efficiency and emissions performance.
• Reduced valvetrain inertia and direct actuation (vs. pushrods) support higher engine speeds with durability.

Together, these factors explain why DOHC inline engines are prevalent in modern performance and efficiency-focused designs.

Exceptions and Notes

Branding like “Twin Cam” generally corresponds to DOHC in inline engines, but always verify the specific engine. Some systems use advanced cam phasers or “cam-in-cam” mechanisms for finer control, yet the engine still physically has two camshafts in an inline DOHC layout. Balance shafts, often present in inline engines to reduce vibration, are separate components and not camshafts.

Summary

An inline DOHC engine has two camshafts total—one for intake and one for exhaust—because it has a single cylinder head. Multi-bank DOHC engines, such as V or flat configurations, typically have four camshafts, with two per head.

How many camshafts does a DOHC inline 4 cylinder have?

two camshafts
Dual overhead camshaft – DOHC engines use two camshafts on top of the engine’s cylinder head. Each one controls a different set of valves. DOHC engines typically have four or five valves per cylinder and are commonly found in larger, high-performance engines.

How many camshafts does a SOHC V 8 engine have?

A SOHC (Single Overhead Cam) V8 engine has two camshafts, with one camshaft operating all the valves for both cylinder banks. Because a V8 engine has two banks of cylinders, each bank gets one camshaft, totaling two camshafts.
 
Here’s a breakdown:

• SOHC: Stands for Single Overhead Camshaft. 
• V8: Means the engine has eight cylinders arranged in a V-shape, creating two banks of four cylinders. 
• One camshaft per bank: In a SOHC configuration, there is a single camshaft located in the cylinder head to operate both the intake and exhaust valves for that entire bank of cylinders. 
• Total: Since there are two banks of cylinders, a SOHC V8 engine uses two separate camshafts, one for each bank. 

Which is faster DOHC or SOHC?

A DOHC (Dual Overhead Cam) engine is generally faster and offers higher performance than a SOHC (Single Overhead Cam) engine due to independent control of intake and exhaust valves, leading to better airflow, higher horsepower, and increased RPM capability. However, SOHC engines are simpler, lighter, and less expensive to manufacture and maintain, making them a suitable choice for applications where peak performance isn’t the main priority. 
This video provides a visual comparison of SOHC and DOHC engines: 59sFTS-SimulationYouTube · May 29, 2024
DOHC (Dual Overhead Cam)

• How it works: Two camshafts operate the valves in the engine head, with one dedicated to intake valves and the other to exhaust valves. 
• Advantages:
  • Higher Power Output: Independent control allows for more precise valve timing, better airflow at high speeds, and greater potential for horsepower and torque at higher RPMs. 
  • Higher RPM Capability: The simpler valve train (lacking rocker arms) and optimized airflow contribute to the engine’s ability to reach higher revs. 
  • Better Airflow: More valves per cylinder (often four) and the ability to optimize valve size improve the engine’s breathing. 
• Disadvantages:
  • Complexity and Cost: Requires more components, making it heavier, more complex, and more expensive to manufacture and maintain. 

SOHC (Single Overhead Cam) 

• How it works: A single camshaft in the cylinder head operates both the intake and exhaust valves. 
• Advantages:
  • Simplicity and Cost: Has fewer parts, resulting in a simpler, lighter, and more affordable design. 
  • Lower Maintenance: Its simpler configuration makes it easier and less expensive to work on. 
• Disadvantages:
  • Lower Performance Potential: One camshaft controlling both sets of valves limits precise timing and can restrict airflow and power at higher engine speeds. 
  • Less Efficient at High RPMs: The design is less optimized for high-RPM performance compared to a DOHC engine. 

This video explains the pros and cons of SOHC engines: 50sLive And Lets Ride PHYouTube · Nov 26, 2020
In summary, if you prioritize speed and high-end performance, a DOHC engine is generally the faster choice. If efficiency, cost, and simplicity are more important, an SOHC engine is a practical alternative.

How many camshafts are in a DOHC?

A DOHC engine has two camshafts per bank of cylinders in the cylinder head. The term “DOHC” stands for “Dual Overhead Cam,” meaning there are two camshafts, one for the intake valves and one for the exhaust valves. For example, a DOHC inline engine would have two camshafts in total, while a DOHC V-engine with two banks of cylinders (like a V6 or V8) would have four camshafts, with two on each head.
 
How DOHC works:

• Dual Cams: Each cylinder head has two camshafts. 
• Separate Functions: One camshaft is dedicated to operating the intake valves, and the other is for the exhaust valves. 
• Improved Performance: This setup allows for more efficient timing, better airflow, higher engine speeds (RPMs), and increased horsepower compared to single overhead cam (SOHC) engines.