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Original Message
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| RE: Headers V's Cast Iron Exhaust manifolds |
| By Ted Young - 10/07/2000 10:08:22 PM; IP 152.163.207.63 |
Ian,
From what I've read, headers offer better exhaust scavenging than cast iron manifolds. With cast iron manifolds, in which the passage ways merge before the collector, the manifold is almost always filled beyond its capacity. Exhaust gasses from one cylinder will build up in the exhaust port of other cylinders as a result. So when a cylinder tries to push out its exhaust gasses when its exhaust port is already filled, and the exhaust manifold is already filled beyond its capacity on top of that, it makes it hard for an engine to get rid of exhaust. With headers, the tubes do not merge before they meet the collector so exhaust charges from one cylinder dont get built up in the exhaust tubes and ports of another. Plus, headers have larger diameter tubes than exhaust manifolds so they can support greter quantities of exhaust. There are some iron exhaust manifolds that have tubes that do not meet before the collector and they flow pretty well, but tube headers will flow more air. I hope all of this helps. I had to read about it a couple of times before I really understood it well. Good luck. I dont know what type of exhaust manifolds you are taliking about, but I know the ones off of my 390 2v in my Galaxie had to be the worst desighn ever.
Ted |
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