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On 11 Jun 99, at 13:40, The Phantom Menace wrote: > Anyway, it has been found thˆTÐ port and polish of the heads, that > polishing the intake ports actually detracts from performance. The > reason is the emulsification and atomization of the fuel is better > achieved with a slightly rough surface. On the other hand, the exhaust > port needs to be 'baby butt' smooth, as that helps with the exhaust > scavenging that the system needs. Remember, on a high hp engine, most > run extractor exhaust and scavenging can be a problem. I believe it is well know that a certain amount of turbulence in the intake helps to mix the incoming mixture. And, yes, laminar flow on the way out maximizes exit flow. > I have seen hp results on a 2.0L engine that had a port, then a port and > polish on the same heads. The gain of 15 hp with the port and no polish > is nothing to be scoffed at, and the added benefit is it costs less to > port and not polish! 15 hp sounds like a lot. Did this job perhaps include higher lift on the valves to take advantage of the porting. I think there is a nice chart in the Bill Fisher book that shows how the value of porting is only really realized at higher lifts. Still, I port, per Bill Fisher with the later Gene Berg mods, and continue to use stock lift. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Too much? Digest! mailto:type3-d-request@vwtype3.org Subj=subscribe