Cylinder Head Choice
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| − | The runners are the ports in the heads, one intake and one exhaust port for each cylinder. The intake runner connects the intake manifold to the intake valve and the exhaust runner connects the exhaust valve to the header or exhaust manifold. | + | The runners are the ports in the heads, one intake and one exhaust port for each cylinder on conventional two-valve heads. The intake runner connects the intake manifold to the intake valve and the exhaust runner connects the exhaust valve to the header or exhaust manifold. |
There are many ways to compare cylinder heads when doing an engine build, but the two main ones are runner volume and CFM of air flow through the runner at a certain valve lift. This is done on a flow bench where air is pulled through the runners at a 28" depression of water. In other words, more and more vacuum is applied to the runner until there is enough vacuum to pull a 28" high column of water up into a tube (manometer). The volume of air that is passing through the runner is then measured and recorded. You would start with the valve off its seat at 0.100", then test again with the valve off its seat at 0.200" and so forth through the range of valve lift that you're testing. | There are many ways to compare cylinder heads when doing an engine build, but the two main ones are runner volume and CFM of air flow through the runner at a certain valve lift. This is done on a flow bench where air is pulled through the runners at a 28" depression of water. In other words, more and more vacuum is applied to the runner until there is enough vacuum to pull a 28" high column of water up into a tube (manometer). The volume of air that is passing through the runner is then measured and recorded. You would start with the valve off its seat at 0.100", then test again with the valve off its seat at 0.200" and so forth through the range of valve lift that you're testing. | ||
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