Re: Spec Miata / Heads
Posted: Thu Oct 23, 2014 10:26 am
My understanding is that the top 6 'on track' finishers were called to impound for all races - so that if any of the 3 podium finishers were penalized there would be backups to take their place. In the case of the SM race, tech had decided to check several specific things on the top 6 in impound, but this list did not include removing valves from heads to check the protested plunge cut issue. I believe this first impound inspection was completed on Friday after the race, and all top 6 finishers passed. Tech then inspected the 9 protested cars, which took up a lot of Saturday. 8 of the 9 were found to violate the rule specified in the protest, and the 9th head was found to violate a of different rule section (relief cut near a one valve). An appeal was quickly turned in, and it took until late Sunday before the appeal was denied and all 9 protested cars were penalized.
FYI, here's a comment from SM'er Steve Scheifler who seems to have some detailed knowledge this issue, along with a link to photo's that illustrate the specific area in question (not of the penalized heads):
"As others have suggested, the degree of "blending" of the plunge cut edges in the protested heads varied from arguably nothing with no tool marks but "suspiciously smooth", to clearly visible tool marks and significant removed metal. The fact that some were so obvious only increased the scrutiny on the rest. And that's where there is still some debate. At least one machinist is adamant that even if it weren't routine to knock sharp edges off after cutting, the edge left from one cut to the next varies greatly depending on the shape of the casting at each port, the cutter, and just tolerances in the process. So a uniform sharp edge may not exist to begin with, and even routine cleaning can dull one. It is his contention that if his head failed then many heads would fail the "sharp edge feel test" even though they had not been intentionally altered and had no sign of tool marks. I have no evidence one way or the other but I think it needs to be investigated before rules are changed."
http://mazdaracers.com/topic/4783-writi ... 3-4/page-2
Dick
FYI, here's a comment from SM'er Steve Scheifler who seems to have some detailed knowledge this issue, along with a link to photo's that illustrate the specific area in question (not of the penalized heads):
"As others have suggested, the degree of "blending" of the plunge cut edges in the protested heads varied from arguably nothing with no tool marks but "suspiciously smooth", to clearly visible tool marks and significant removed metal. The fact that some were so obvious only increased the scrutiny on the rest. And that's where there is still some debate. At least one machinist is adamant that even if it weren't routine to knock sharp edges off after cutting, the edge left from one cut to the next varies greatly depending on the shape of the casting at each port, the cutter, and just tolerances in the process. So a uniform sharp edge may not exist to begin with, and even routine cleaning can dull one. It is his contention that if his head failed then many heads would fail the "sharp edge feel test" even though they had not been intentionally altered and had no sign of tool marks. I have no evidence one way or the other but I think it needs to be investigated before rules are changed."
http://mazdaracers.com/topic/4783-writi ... 3-4/page-2
Dick