A crankshaft is a vital component of your vehicle’s engine. A V8 engine often has one crankshaft, although some engines have more than one. In the V8 engine world, there are only two major types of significant crankshaft designs: flat and cross.
Here is everything you need to know.
What is a V8 Crankshaft?
Crankshafts are not new technologies – they have been in existence for more than one hundred years. They have had a wide application, including water mills, sawmills, and boat paddling.
A crankshaft is a shaft that is located at the bottom end of your vehicle’s motor and is driven by a crank mechanism that consists of several cranks and crankpins. The engine’s connecting rods are attached here.
A crankshaft is mechanical, and its role is to bring about either a reciprocating motion or a rotational motion, depending on the type of engine.
Where your car has a reciprocating engine, the work of the crankshaft is to convert the reciprocating motion of the car’s piston into a rotational motion and vice versa when the vehicle has a reciprocating compressor.
The crankshaft is usually attached to a flywheel whose purpose is to minimize the pulsating effect of the four-stroke or two-stroke cycle.
Likewise, the crankshaft might have a torsional damper at the other end whose work minimizes the thrust effect of torsional vibrations caused along the crankshaft’s length.
What Does a Crankshaft Do In a V8?
A crankshaft causes your V8 to move by converting the piston’s reciprocating motion into a rotary motion. Here is an illustration of how a four-stroke engine’s crankshaft works:
Step 1: When the engine piston makes a downward stroke, its motion is transferred to the crankshaft through the connecting rods.
Step 2: the crankshaft then converts the linear motion produced by the piston into a rotational motion, which it then transfers to the camshaft.
Step 3: upon the camshaft receiving the rotational motion, it causes the inlet valve to open. This allows into the combustion chamber a mixture of air and fuel.
Step 4: the piston then makes an upward stroke and compresses the mixture of air and fuel, causing the camshaft to close the inlet and exhaust valves. The first complete revolution of the crankshaft ends when the compression ends. The finalization of the compression process brings about ignition, and the compressed mixture releases heat.
Step 5: the heat causes the piston to make a power stroke – it forces the piston to make another downward move. Again, the piston’s reciprocating motion is sent to the crankshaft, which transfers it to the flywheel.
Step 6: the flywheel stores the received motion then drives your vehicle’s wheels.
Step 7: the piston moves further down (makes an exhaust stroke), and that motion is received by the camshaft, which opens the exhaust valve and closes the inlet valve, and exhaust gases are pushed out of the combustion chamber by the piston. The second revolution is completed at this point, meaning a power cycle of the 4-stroke engine also completes.
Step 8: it goes back to step 1, and the entire process repeats itself.
Types of Crankshafts in V8 Engines
As already noted, you are likely to find one of the two types of crankshafts in your V8 – there’s the flat-plane crank and the cross-plane crank.
Flat plane cranks are mostly used to design hypercars and supercars. They are designed with a spaced four-cylinder cranking or single crankpins and always work by alternating from bank to bank. This attribute helps in the reduction of header complexes.
This type of crankshaft usually reps quickly as they do not rely on heavy counterweights. The downside of this is that the crankshafts experience secondary vibrations.
- Since they are lightweight, they produce a great balance
- They are easy to tune for maximum performance
This type of crankshaft is most common in hot rod engines. In most cases, it is found in American muscle cars such as Coyote and Hemi. The crankshafts got their name from the arrangement of their crankpins – it has 4 crankpins that are arranged in two ninety-degree levels.
The arrangement makes a plus (+) shape when you look at it from the end of the four points, hence the name ‘cross-plane.’
The cranks produce the standard muscle vehicle noise – a rumbling sound that does not produce vibrations like flat-plane cranks. However, its ability to scavenge exhaust fumes is inferior to that of a flat-plane crank.
- Cross-plane crankshafts are smooth
- There is no vibration in their performance
- The cranks have more torque
- They are not lightweight
- They need a big crankcase
Frequently Asked Questions (FAQs)
Does V8 have two crankshafts?
The answer is yes and no, depending on the individual V8 car in consideration. However, very few have two crankshafts. More than 99% of V8s will usually have ONE crankshaft.
V8 with Bentley engines (W12 engines) have a high likelihood of having 2 crankshafts, unlike their counterparts with an 8 cylinder V engine.
Likewise, a car can contain either one or two camshafts per head. V8 cars have two heads, including those using an 8 cylinder V engine.
On How Many Crankshafts Are in a V8
Crankshafts are important components of your V8 car’s engine. They are responsible for your car’s movement since they convert the engine piston’s motion into a rotational motion which is then sent into the camshaft.
V8 engines may have only two types of crankshafts: the flat-plane crankshaft and the cross-plane crankshafts. Flat-plane shafts are primarily used in sports cars and high-end exotic cars.
They alternate from bank to bank, are lightweight, and have secondary vibrations. Cross-plane crankshafts are mostly used in American makes, have a rumbling sound and vibrations-free performance.
Overall, a huge percentage of V8 cars have a single crankshaft. Only those with Bentley engines are likely to have two crankshafts.
Hi I’m Marshall based in 1478 Doctors Drive Santa Monica, CA. I’m your DIY Car Repairman with more than 5 years experience in automobile repair, a skill I learned from my old man.
I started this blog to share my experience on both simple and technical aspects of your car.