The other negative feature of the side-valve engine design is that the air/fuel mixture has to reverse flow direction for the intake and exhaust strokes.
#STEVE MEADE DESIGNS DISTRIBUTOR BOX FULL#
The basic engine design did not allow the side-valve engine to take full advantage of the newer fuel. This reduced height between two flat surfaces further impedes air flow. In order to increase the compression ratio, the distance between the top of the engine block and the roof of the cylinder head is reduced. To use this fuel efficiently, it is necessary to increase the compression ratio. This is a problem in a side-valve engine design.Īnother problem with the side-valve engine design was that after World War II, the available fuel had a higher octane rating. This inefficiency of air flow is not a huge problem at low engine revolutions, but if the engine designer wants a higher revving engine, then one of things that has to happen is to get the air flow mixture into the engine as fast as possible and get the spent air/fuel out as quickly as possible. Any spent air that remains in the cylinder during the next compression stroke takes up space in the cylinder that should be occupied by the air/fuel mixture. The same thing happens during the exhaust stroke as the spent air is not efficiently removed from the cylinder head. There are too many obstructions that cause turbulence and air flow eddies that impede efficient air movement. The flat surfaces and internal corners are not conducive to good air flow. The intake air/fuel mixture flow path is not smooth. On the intake stroke, the intake valve will open and the suction caused by the downward movement of the piston will draw the air/fuel mixture into the cylinder and cylinder head. The disadvantage of the side-valve engine is that the air flow characteristics of the design are far from optimal. So, in general, the more volume of fuel that you can burn and the faster that you can burn it, then the more power that the engine will produce. The purpose of automotive engine design is to convert the energy in the fuel into energy that can be used to move the car forward. By compressing the intake mixture in the location of the spark plug, the burning of the fuel mixture is enhanced. With the cylinder head design as I have shown it in the sketch, during the compression stroke the intake mixture is forced into the cylinder head volume above the intake and exhaust valves and directly in the spark plug area. Many side-valve engines do not have this clearance reduction and the roof of the cylinder head is at a common distance all across the cylinder head which reduces the compression of the air/fuel mixture compared to what I have shown. For my sketch, I have shown a reduced clearance between the roof of the cylinder head and the top of the block in the area of the piston. Typically the top dead center of the piston travel in these engines is right at the top of the engine block. The cylinder head that I have shown in the above sketch is typical of a slightly high compression side-valve design.
As a result, there is very little in the cylinder heads other than the spark plugs. In order to try to explain this engine design, I have prepared the following sketch of a side-valve engine design.Īs can be seen from the above sketch, in a side-valve engine design the intake and exhaust valves are located in the engine block – not in the cylinder head. In North America, the most common, or at least the most famous, side-valve engine was the Ford side-valve V8 or “Flathead” V8 that was in their North American cars from 1932 to 1953.Īs can be seen from the above image the name “Flathead” came from the rather flat exterior surface of the cylinder heads.
As a result, I thought that I would try to further explain some of the technical aspects of automobile design and performance. My day job is as a consulting engineer (although not in the automotive industry) so I have an engineering interest in the technical aspects of automotive design.
It seems that I often refer to the superiority of the overhead valve engine design as compared to the side-valve or “flathead” engine design.
0 kommentar(er)
