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On 4 Mar 98 at 19:06, Big Al wrote: > "...a rough intake manifold promotes turbulence which > >is a good thing. " > > I'm not so sure about this. If this is so then why do racers want the > intakes, valves, and even the interior throats of carbs polished??? The fact that someone wants something doesn't mean that there's an advantage to it. Consider the fact that airplane designers have been trying to design airfoil surfaces with just the right degree of roughness for years because it actually reduces drag. The problem is that it causes problems in bad weather with icing. > Air volume at a higher rate! Just because something is obvious doesn't mean that it is true. Actually, I'm not sure of this either, I don't own a flow bench and have no experience with one, but I got this information from someone who owns and uses one. His feel for these things is usually good. I don't recall if Gene Berg had any comments on this. He's usually done his homework, too. > Rough pipes decrease the flow velocity of the air which makes the engine > starve for fuel mixture right? I can see the "rough causes mixture" in > theory, but if this is so, wouldn't VW have added a texture to the pipe? > > And for polishing the exhaust manifold... Where? Do you mean the interior > of the heater boxes? I am unclear as to the location you mean. This comment was general. In our VWs I agree that there is no need for any polishing in the heater boxes because the pipe ID is already smooth, but there is some advantage to smoothing the interior of the exhaust ports in the heads. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA *******************************