From outdoor sports fields to our backyards, lawnmowers have kept the grass low and our properties pretty. There are just so many variations of them in regards to shapes and sizes. Now, if you ever paid attention to the engine of a lawnmower, you may have noticed the initials “OHV” on it. What does this mean exactly?
OHV stands for “Over Head Valve.” An OHV engine is a type of engine on which the valves are located above the combustion or ignition chamber. Lawnmowers that utilize this type of engine are designated as “OHV lawnmowers.”
Now, let’s take a deeper dive into the world of lawnmower engines and learn how they function and what are their benefits and drawbacks. We will also go over some other engine options to see which one suits you best.
What Is an OHV Engine Lawn Mower?
First, let’s better understand what an internal combustion engine is. Of course, there are numerous variations in designs and concepts, but the main components in a typical IC engine are more or less the same. These include:
- Crankshaft – Converts reciprocal motion (rhythmic up-down or forward-backward motion) into a rotational motion.
- Camshaft – Does the exact opposite of the crankshaft. Its purpose is to open and close the valve to control the air that goes in and out of the engine.
- Piston – This is the cylinder-shaped structure that you see continuously moving up and down in an engine. It transfers the energy of the combustion to the crankshaft.
- Valves – The valves are the parts that regulate the flow of air and fluid into the combustion chamber.
- Cylinder/Engine Block – This is the main body of the engine. It houses all the separate parts and gives it a sturdy platform.
- Connecting Rod – This part connects the crankshaft to the cylindric pistons.
- Spark Plug – Its name gives away Its purpose. It is a small device inside the chamber that supplies electric current or a “spark.” This, in turn, causes the mixture of fuel and air to ignite.
Most standard OHV engines feature these parts in some form or another. But, the main differences lie within the valves and the camshaft.
This engine’s name derives from the placement of its valves. The valves are “overhead,” meaning they are placed on top of the main combustion chamber. In other words, they are located in the cylinder head, which is the top portion of the cylinder/engine block. On traditional “flathead” engines, you will see the valves in the middle of the block.
The other part of the equation is the camshaft. In an OHV engine, the camshaft is fixed invariably in the cylinder, next to the pistons. So, the valves are at the top while the camshaft is at the bottom.
Are OHV Engines Good?
Back in the days, manufacturers mainly utilized the side-valve or flathead design for lawnmowers. This was a simpler design that required less lubrication. It was not until the late 90s that the overhead engine started to gain popularity and being produced in mass.
The OHV variation offers a more compact size. Though the valves require more moving parts, the placement of these components makes for an efficient engine design. This means that you get more power for the same size displacement compared to other engines.
OHV engines are a popular choice thanks to their durability. For lawnmowers, it is a particularly beneficial trait to have. You will find that this engine will serve you for a long time. You will be a hard fit to find another engine that matches the mileage you will get out of this one.
What Are the Disadvantages of OHV Engines?
OVH engines have a limited RPM and lower engine speed because the components of the OHV engine have more inertia, making them harder to control at a higher speed.
Their other downside is maintenance. With a flathead engine, all the components are located in one case, close to each other. Thus, you can easily splash oil on all the parts without many intricacies.
However, this is not the case with an OHV engine as this design requires the use of an oil pump and oil filter. These are additional parts that you have to maintain for the engine to last longer.
OHV engines will typically cost you more than side-valves engines due to the additional components and more complicated structure. Therefore, the price of your lawnmower is also going to increase with an OHV engine.
Which Is Better: OHV or OHC Engine?
As previously mentioned, OHC stands for “Over Head Camshaft.” Here, both the camshaft and the valves are located above the body of the engine. But, there are some noticeable differences between the two types of engines.
OHV offers more power and a more compact design. It is also more durable than other standard types of engines. Besides, OHV engines are usually — although not always — cheaper than OHC engines.
On the other hand, OHC engines offer more compression as they have fewer parts for the valves. This brings about a couple of benefits. First, the OHC runs more efficiently and smoothly than the OVH. Second, it can also produce more RPM than a standard OVH and give you more control. You can have more precision at greater RPM.
The downside of the OHC is that it requires an additional timing chain or belt, which adds to the number of parts that require maintenance.
Ultimately, we find that the OVH offers better service over an extended period. However, you will not get ripped off by choosing an OHC. If you feel the added maintenance is not much of an issue, you can go with an OHC.
An OVH engine has been a staple of lawnmowers for quite some time, and it is easy to see why. With terrific power and endurance, this engine is a great choice for any mowing purposes.
