The internal combustion of the engine creates fire through the spark plugs.
This ignites the air-fuel mixture and moves the crankshaft. To maximize engine performance, car designers create a sequence that drives each cylinder. The ignition of each engine cylinder is unique on car models.
The sequence of ignition is critical for smooth engine operation. In a typical 4-cylinder engine, the preferred sequence is 1-3-4-2. Most modern cars use their electric control unit (ECU) to control the ignition sequence, while in old gasoline engines the distributor determines the location of the spark plugs.
Most engines turn clockwise. However, some engines may turn counterclockwise due to mechanical configurations.
Chevrolet 350 Small block Firing Order
If it is a factory-made camshaft, then expect an order of 1-8-4-3-6-5-7-2, but if you have a 4/7 swap camshaft, then expect an order of 1-8-7-3-6-5-4-2
If you have replaced the camshafts with a different ignition sequence, your ignition cables will also be modified.
How do you count the cylinder numbers cylinders?
The numbers start from the front and continue to the back. At the front of the engine, you see pulleys, the alternator, and the water pump. Some V-engines can be numbered in rows, so you have the first row from 1-2-3-4 and then the next row, from the front, from 5-6-7-8.
With others, you would number them like you would number an in-line four-cylinder engine, where you have 1-3-5-7 and 2-4-6-8. The numbering of the cylinders can be complicated by the fact that the manufacturers may use a different numbering for individual engines. It is advisable to look up the correct sequence in your manufacturer’s manual.
Different types of firing orders
The reason why manufacturers have a firing sequence is to reduce torsional vibrations while at the same time enabling the safe emission of exhaust gases. With a sequence, there is little interference between cylinders, which promotes manifold recovery. An arrangement is difficult with fewer cylinders.
It is important to separate the outflowing cylinders so that the back pressure does not promote the escape of exhaust gases.
The simplest engine is the single cylinder arrangement. With this arrangement, you will experience a power stroke every 720 degrees. The piston has a head and is connected to the crankshaft via a connecting rod. The rod rotates in an oscillating movement.
If you enlarge the cylinders to a two-stroke engine, you have power pulses of 720 degrees/2 or a crankshaft rotation of 360 degrees. In this scenario, where one piston is in the compression stroke and waiting for its working stroke, the other piston is in the exhaust stroke and about to enter an intake stroke.
With horizontally counter-rotating engines, power pulses occur with every 360 degree rotation of the crankshaft. This means that during the revolutions the crank throws are out of phase by 180 degrees. In horizontally opposed engines, the connecting rod and piston are opposite each other. This type of engine often occurs in small engines.
An engine with a different ignition sequence is the radial engine. In this case the firing order is centered on a circle. If you have 7 cylinders, you can find an ignition sequence of 1-3-5-7-2-4-6.
If the firing order is even, the angle between the individual firings is the same. If you have a four-stroke engine, you can obtain the ignition interval by dividing the number of cylinders by 720 degrees. With an odd firing order, not all angles are the same. You can have one with a 90-degree angle, while another has an ignition interval of 150 degrees.
Depending on the design of the crankshaft, you will find that the cars with even firing order will sound smooth, while the cars with uneven firing order will sound throaty.
Problems with the ignition system will cause the vehicle to misfire. A misfire happens either in the intake or exhaust valves, not in the combustion chamber. Unburned fuel is the main cause of misfiring, and a loud noise can be heard or flames can be seen outside the exhaust. On cars with shortened exhaust pipes the flames are visible.
The reasons for backfiring vary and include a disproportionate amount of air entering the combustion system along with insufficient fuel. The result is that the mixture does not ignite and misfire occurs. This unburnt mixture passes through the exhaust system where it re-ignites due to the hot components. If you also have an abundant air-fuel ratio, you will also misfire.
The spark plugs ignite the air-fuel mixture via a timing system.
If this is too early, the mixture enters the intake valves before ignition. This leads to an ignition which travels through the carburetor and can cause severe fires.
Incorrect timing of the ignition process leads to misfiring. Since there is an anti-lag, you will experience loud explosions. If the wiring is not done correctly, you will have problems with the ignition timing. It is a good idea to check the fuel pump and air filters for clogging. A defective catalytic converter can cause misfiring.
Inside the internal combustion engine there are spark plugs in each cylinder. This creates a spark that ignites the air-fuel mixture, allowing the crankshaft to move. To increase the efficiency of the engine and reduce vibrations, car engine manufacturers have an ignition sequence for the spark. In modern engines the ignition sequence is controlled by the ECU. The firing order starts with the first cylinder at the front end of the car. This is the cylinder with the number 1.
In most four-cylinder engines, the numbering is 1-3-4-2, while in the Chevy 350 small block engine the firing order is 1-8-4-3-6-5-7-2. If the timing of the ignition is incorrect, misfiring will occur. In this case more air than fuel may enter the combustion chamber. This leads to unburned fuel which finds its way to the exhaust manifold where it ignites and causes a loud bang or fire.
Hi, I’m Magnus, the owner and the writer of Mechanic Base. I have been working with cars for 10 years, specialized in diagnostics and troubleshooting. I created this blog because I was tired of finding false information on the web while looking for repair information. I hope you enjoy my content!