That brings us to the firing order. Now all things being equal, the most efficient firing order is that of F1 cars more or less – which is 1-5-3-7-4-8-2-6, with some slight variations on that.  The important thing is that no two adjacent cylinders fire sequentially; i.e. no, 1-2. 7-8. 6-7. or so forth as with most major automakers. (Note: all firing order references are to one bank numbered 1-4 and the other 5-8.)  Now, the theory behind this is that when one cylinder fires, it will heat up the cylinder wall, and expand the cylinder; albeit a minuscule amount, but it expands nonetheless.  This produces a problem in reference to the cylinder next to it when it fires.  First is the fact that now it has to squeeze through a smaller bore due to the expansion caused by the other cylinder.  Secondly, it will be dealing with a heated charge of air due to the rise in overall temperature due to the common wall/combustion chamber areas.  Thirdly there is the matter of undue stress on the cylinder wall as it is rapidly forced one way and then must change direction to push 180 degrees opposite.   This is why the firing order of an engine is important in the makings of a race motor, and some things that were taken into consideration by the high rpm crowd of F1 guys.  It is also something that is of interest when trying to understand just what a motor does.  There is also a lot of involvement with intake runners and fuel charges when dealing with firing orders, though a lot of that is only a carburetor discussion; mass quantities of it can be ommitted for the Sequential Port Fuel Injection crowd.

This is why in some performance operations people opt for a cam that “swaps” a couple of cylinders on the firing order, such as a 4-7 swap on some Chevy’s.  It has to do with the increase in power garnered from the correct usage of the available fuel charge and the increased efficiency of the engine overall.