Which is the Best Engine Valvetrain Design? OHV, SOHC, DOHC or Flathead | Pros and Cons

the valve train is a mechanical system in an internal combustion engine that manages the opening and closing of the intake and exhaust valves its purpose is to regulate the timing of these valve operations to allow the intake of air fuel mixture into the combustion chamber and the expulsion of exhaust gases during the intake stroke the intake valves are responsible for controlling the flow of the air fuel mixture into the combustion chamber during the exhaust stroke the exhaust valves regulate the flow of spent exhaust gases out of the combustion chamber by coordinating the timing of valve openings and closings the valve train ensures efficient combustion and optimal engine performance the valve train is consists of various components that work together to control valve operation like camshaft valve valve spring lifters push rod rocker arm and timing mechanism let's take a look at these parts in details starting with camshaft the camshaft is a rotating shaft that contains specially shaped lobes or cams it is driven by the engine's crankshaft through a timing belt chain or sets of gears the lobes on the camshaft have profiles designed to open and close the valves with precise timing the camshaft rotates at half the speed of the crankshaft in a four-stroke engine one revolution for every two crankshaft revolutions valves are usually made of metal and serve as the openings for the intake and exhaust passages in the cylinder head when the camshaft lobes actuate the valves they open and close to allow the flow of gases in and out of the combustion chamber most modern engines use poppet valves sleeve valves slide valves and rotary valves have also been used at times poppet valves are typically opened by the camshaft lobe or rocker arm and closed by a valve spring valve springs are helical Springs positioned around the valve stems the valve springs ensure proper seating of the valves and prevent them from floating during High engine speeds lifters also known as tappets are components that transfer the motion from the camshaft lobes to the valves a lifter is a cylindrical component that rides on the camshaft to actuate the intake and exhaust valves push rods are long slender rods that transmit the upward movement of the lifters to the rocker arms they are typically used in overhead valve engines to transfer the motion from the lower camshaft position to the valves located in the cylinder head rocker arms are pivoting levers that transfer the motion from the push rods to the valves they convert the linear motion of the push rods into the required pivoting motion to open and close the valves the timing mechanism synchronizes the rotation of the camshaft with the rotation of the crankshaft to ensure precise valve timing this mechanism typically utilizes timing belts chains or gears to connect the camshaft and the crankshaft these components works together to ensure that the opening and closing of the valves occur at the correct moments in the engine's operation maintaining proper valve timing is essential for optimal engine performance and efficiency if the timing is off it can lead to decreased power poor fuel efficiency and potential engine damage therefore the timing mechanism plays a crucial role in the overall functioning of the engine the operation of the valve train is coordinated with the Piston movements within the engine cylinders to achieve the desired intake compression power and exhaust Strokes the camshaft profiles valve springs lifters push rods and rocker arms work in harmony to open and close the valves at the correct time allowing for efficient combustion and power generation types of valve train different engines May utilize variations in valve train designs such as overhead valve overhead camshaft or dual overhead camshaft configurations Advanced Technologies like variable valve timing and variable valve lift allow for even greater control over valve operation optimizing engine performance across various operating conditions an overhead valve engine also known as a push rod engine or an i-head engine is a type of internal combustion engine design commonly used in a wide range of vehicles this configuration allows for a more compact cylinder head design compared to engines with valves located directly in the head overhead valve engines offer several advantages the use of push rods and rocker arms allows for a more compact cylinder head design making the engine lighter and more compact overall overhead valve engines are generally less expensive to produce compared to overhead camshaft engines as they have a simpler valve train system overhead valve engines are known for their high torque output particularly at lower RPMs this makes them well suited for applications that require low end power such as Towing and off-roading however these engines have some limitations the push rod and rocker arm mechanism May limit the engine's maximum rpm capability the design of the valve train and overhead valve engines May limit the engine's breathing efficiency which can impact its overall performance this means that a small overhead valve engine will not be very efficient this design is more suitable for larger V6 and V8 engines you won't find this engine in a modern compact car Chrysler Hemi V8 gmlsav8 are examples of overhead valve engines an overhead camshaft engine is a type of internal combustion engine in which the camshaft responsible for operating the engine's valves that are positioned within the cylinder head above the combustion chamber in an overhead camshaft engine the camshaft is driven by the crankshaft through a timing belt timing chain or gears single overhead camshaft and dual overhead camshafts are variations of overhead camshaft engines they refer to the number of camshafts present in the engine design in single overhead camshaft engine there is one camshaft per Bank of cylinders this single camshaft is responsible for operating both the intake and exhaust valves in the engine therefore a straight engine has a total of one camshaft and V engine or flat engine has a total of two camshafts one for each cylinder Bank these are commonly found in a variety of vehicles and they are widely used in mainstream Automotive applications and can provide a good balance between performance efficiency and cost effectiveness it is simpler and lighter version of the more complex dual overhead cam setup the single overhead cam setup involves less moving Parts hence is easy to repair and it is less expensive to maintain and manufacture the benefit to the overhead cam setup is that it allows for more intake and exhaust valves meaning fuel air and exhaust can move more freely through the engine adding power more the power more is fuel consumption thus when talking in the terms of single overhead cam versus dual overhead cam fuel efficiency a single overhead cam is more fuel efficient in single overhead cam setup the camshaft is usually placed in the middle of the head which denies the spark plug in its ideal location this designs have less control over valve timing as compared to dual overhead cam it is simply a single camshaft regulating both the inlet and the outlet of gases thus this engine will gain heat faster than dual overhead cam in a dual overhead camshaft engine also referred to as twin cam engines there are two camshafts per Bank of cylinders one camshaft is dedicated to operating the intake valves while the other camshaft is responsible for the exhaust valves in a street engine there are two camshafts one for intake and one for exhaust valve in V engine or flat engine where the cylinders are arranged in a v-shape or horizontally opposed you would have four camshafts each cylinder bank would have two camshafts one for the intake valves and one for the exhaust valves advantages of Dual Overhead camshaft by having four valves in a cylinder instead of two a larger portion of the area can be used to let the air in and exhaust out the engine can make more power if more air enters the cylinder and it wastes less power if it is easier to pump the exhaust out of the cylinder at higher engine speeds the engine pumps a lot of air through the cylinders having four valves per cylinder allows the engine to pump enough air to run and make useful power at these higher speeds most dual overhead cam engines with two camshafts one per cylinder Bank are still capable of providing improved valve control higher RPM capabilities and enhanced performance compared to single overhead cam engines the Dual camshafts allow for more precise control over valve timing and lift contributing to better engine breathing and power output the first production car to feature a dual overhead camshaft engine was built in 1910 highlighting the early adoption of this configuration from the 1940s onward the use of these engines gradually increased leading to their widespread adoption and many automobiles by the early 2000s one of the earliest example was the 1906 Grand Prix winning Fiat s76 also known as the Beast of Turin this vehicle featured a massive 28.5 liter inline 4 Engine with dual overhead camshafts pujo's early double overhead camshaft engine proved quicker than anything else on the track armed with the new dual overhead technology it won the 1912 French Grand Prix in 1913 Peugeot used its dual cam engine to become the first foreign automaker ever to win the Indianapolis Grand Prix Flathead also known as a side valve engine or valve in block engine refers to a type of internal combustion engine design where the combustion chamber and valves are located within the engine block resulting in a relatively flat cylinder head the valves are positioned beside the piston in the cylinder rather than in the cylinder head Flathead engines were widely used in early Automotive applications especially in the early to mid 20th century however they have been largely replaced by overhead valve and overhead cam designs in modern vehicles due to the limitations it's worth noting that some enthusiasts still appreciate Flathead engines for their Simplicity vintage appeal and nostalgic charm additionally certain industries such as marine and small engine applications still utilize Flathead designs for their specific requirements Flathead engines were known for their Simplicity and low manufacturing cost however they did have certain limitations in terms of combustion efficiency and performance Flathead engines feature a valve gear system that includes a camshaft located low in the cylinder block this camshaft operates the poppet valves through tappets and short push rods the Flathead design eliminates the need for additional valve train components such as lengthy push rods rocker arms overhead valves or overhead camshafts in a typical Flathead engine the side valves are positioned adjacent to each other on one side of the cylinder however there are also Flathead engines that utilize the less common cross flow or t-head configuration in t head engine the exhaust gas is exit on the opposite side of the cylinder from the intake valve the combustion chamber in a side valve engine is located to the side of the Piston above the valves the position of the spark plug can vary being located either above the Piston or above the valves Flathead engines May utilize pop-up Pistons to increase the compression ratio and optimize the combustion chamber shape to prevent knocking one of the limitations of Flathead engines was the valve design the intake and exhaust valves were located in the engine block alongside the combustion chamber and they were positioned horizontally this design restricted the airflow into and out of the combustion chamber leading to less efficient combustion and reduced power output Additionally the Flathead design limited the compression ratios that could be achieved the flat shape of the combustion chamber and the position of the valves made it challenging to create a compact and efficient combustion chamber design as a result Flathead engines typically had lower compression ratios which affected their overall performance and efficiency despite these limitations Flathead engines were widely used during their time due to their Simplicity affordability and reliability however as automotive technology advanced other engine designs with improved airflow and higher compression ratios emerged eventually leading to the decline in the use of Flathead engines in modern vehicles Flathead engines were widely used in various automobiles including notable models such as the Ford Model T Ford Model A Ford flathead V8 engine and the Ford side valve engine Cadillac also produced V16 Flathead engines for their luxury cars during a specific period the Ford Model T which was introduced in 1908 utilized a four-cylinder Flathead engine it played a significant role in popularizing Flathead engines and making automobiles more accessible to the masses the Ford flathead V8 introduced in 1932 was a groundbreaking development it featured eight cylinders in AV configuration and became highly influential in the Hot Rod and Custom car scene however after World War II Flathead designs gradually gave way to overhead valve designs that offered advantages such as improved performance higher RPM capabilities and better breathing efficiency today while Flathead engines are no longer commonly used in mainstream automobiles they still hold historical and cultural significance restored Flathead engines can be found in vintage and classic car collections particularly in the realm of custom cars and Hot Rods where enthusiasts appreciate their iconic design and nostalgic appeal several notable motorcycle manufacturers such as Harley-Davidson employed Flathead V-Twin engines in their models in early 1900s these engines played a crucial role in establishing Harley-Davidson's reputation and contributed to the development of the American Motorcycle industry Indian another renowned American motorcycle manufacturer also utilized Flathead V-Twin engines in their motorcycles during the pre-war era these engines powered many Indian models and contributed to the company's success Triumph and BSA also featured Flathead engines in their early models the utilization of Flathead engines in early motorcycles contributed to the development of the motorcycle industry and played a significant role in the evolution of motorcycle technology these engines are still celebrated today for their historical significance and are often seen in vintage motorcycle Restorations and collections so that's it thanks for watching if you enjoyed this video share your thoughts in the comments below and don't forget to hit that like button be sure to check out my video on working a four-stroke and two-stroke engine by clicking here thank you [Music]

Channel: The Engineers Post

Views: 779,351

Keywords: ohv, sohc, dohc, valvetrain, overhead valve mechanism, overhead camshaft engine, overhead camshaft vs pushrod, overhead camshaft mechanism, single overhead camshaft engine, dual overhead camshaft

Id: lNnwn8OlPHM

Length: 16min 30sec (990 seconds)

Published: Sat Jul 01 2023