Cord V-8 discussion

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04 Dec 2003 15:57 #1079 by leslie9958
leslie9958 replied the topic: The 180-degree manifold.
Jim O'Brian quote:

Could someone please explain an 180 degree intake manifold. I don't understand what the 180-degree refers to regarding an intake manifold.

When Levavasseur produced/invented the first V-8 in about 1902 it had a 180-degree Flat crankshaft identical to a four-cylinder engine but this produces a Secondary Horizontal Shake of a rather large magnitude. This is why Cadillac developed the 90-degree crankshaft that you see so much today.

A regular ?Log? manifold does not fire as a dual four cylinder it fires from one chamber. This is what the 180-degree manifold gets rid of. That is there are small overlapping pulses in the manifold but some very smooth transferring of suction from one cylinder to the other in line of the firing. Using a 720-degree plot/chart of all the cylinders in their order of fire best shows this. One must first remember that a camshaft lobe does not actually open the valves only for 180 degrees but more like 220 degrees. This overlapping of the valves produces a lot of unwanted interference in the manifold unless it is restricted by the use of a manifold that prevents this from occurring. I may sometime in the future have Josh post a diagram of this to show the opening of the exhaust and the intake valve if someone can provide me with the opening and closing of the intake and the exhaust timing. 4 x 220 degrees =880 degrees obviously more than 720 degrees of a complete cylinder cycle in a four-cycle engine. Some overlap is not very bad but if you are talking about 8 cylinders the overlapping is something like four cylinders interfering with each other instead of assisting one another in the intake cycle. This also has a lot to do with sonic effects between the cylinders altho this primarily is between the exhaust and that cylinders intake, but at this point I don?t believe that it is wise to get into.

What a 180-degrree manifold does basically is to divide the 8 cylinders into two four cylinders which fire at 180-degees apart. What Ford did was to make the manifold fire two cylinders on one side pair up with two cylinders on the other side of the block and make it fire as two four cylinder engines as far as the manifold is concerned. 720 degrees divided by 8 cylinders is 90 degrees firing spread for the eight cylinders. A four cylinder engine fires at 720 degrees divided by 4 cylinders is 180-degrees. The sketch I am preparing will explain this to a great degree, but only if you study it and think about it in some depth.
That is why I color-coded it for simplification. I will also try to send this to Josh in the next several days.

When Ford did this men at Cadillac were quite surprised at the simplicity of Fords development and according to Automobile Quarterly were in great admiration of the design. I can?t argue with that! See page # 239 left hand column. Third edition 1979. It was the third big development in the designing of the V-8 engine.

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