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On 11 Jun 99, at 17:39, Dave Hall wrote: > I'm not polishing the bus heads now it's all together and running very > smoothly (don't you hate saying that too loudly?!), Jim, but would the > roughness help reduce the chance of cracking, and if it passed heat through > the head, would that mean a cooler-running exhaust valve? I don't know if > this is the thinking behind the finish, or just saving costs. I doubt if the roughness would help cracking, although shot peening will. The roughness is just there because that's the as-cast finish. Since the head cools the valve via the seat and guides, a cooler head will lead to a cooler valve. Thus this is one more reason to polish the heads. For the record, I have never bothered doing this either, but the semi-hemi flycut leaves a pretty nice finish. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Too much? Digest! mailto:type3-d-request@vwtype3.org Subj=subscribe