Safety 3/Radio Dave
Well-known member
For what ever this is worth, changes to Sec Mita for 2015
December 18, 2014
Rule GCR 9.1.7.C.1.f.3, regarding cylinder heads, now reads: “The throat area of the port consists of the 90 degree angle at the very bottom of the cast steel valve seat as it transitions to the aluminum casting below. It is permitted to plunge cut the throats in order to correct for core shift that is commonly found in many cylinder heads. The cut must be cylindrical and concentric to the valve guide axial centerline, within a tolerance of .005”, for the entire length of the cut. The radius tangent to the cylindrical and bottom surfaces shall not exceed 0.375". This cut cannot extend further than the specified number below from the bottom of the ferrous valve seat. There can be no tooling or machine marks in the head below this point. The Intersection of the machined surface of the plunge cut to the port casting shall not be altered, except that the area under the short turn radius may be de-burred, with the de-burring not to exceed 1.5 mm in width. The 90 degree bend at the bottom of the valve seat and the aluminum directly below it will be measured with a gauge and must conform to the maximum diameters and depths listed below.”
Additionally, recommended changes to the front suspension were approved. Rule 9.1.7.C.3.p now reads “Inner bushing(s) on the front upper control arms may be replaced with offset bushings.”
“These technical rules came after a series of meetings involving experts from Mazda, NASA, and of course, the SCCA and our Club Racing Board, and we’ve come away from them moving truly in the same direction,” Lisa Noble, SCCA President/CEO, said. “Each meeting brought to light different facts, including the shortage of stock Miata heads now available, and all parties felt that this rule set is the best course of action moving forward.”
December 18, 2014
Rule GCR 9.1.7.C.1.f.3, regarding cylinder heads, now reads: “The throat area of the port consists of the 90 degree angle at the very bottom of the cast steel valve seat as it transitions to the aluminum casting below. It is permitted to plunge cut the throats in order to correct for core shift that is commonly found in many cylinder heads. The cut must be cylindrical and concentric to the valve guide axial centerline, within a tolerance of .005”, for the entire length of the cut. The radius tangent to the cylindrical and bottom surfaces shall not exceed 0.375". This cut cannot extend further than the specified number below from the bottom of the ferrous valve seat. There can be no tooling or machine marks in the head below this point. The Intersection of the machined surface of the plunge cut to the port casting shall not be altered, except that the area under the short turn radius may be de-burred, with the de-burring not to exceed 1.5 mm in width. The 90 degree bend at the bottom of the valve seat and the aluminum directly below it will be measured with a gauge and must conform to the maximum diameters and depths listed below.”
Additionally, recommended changes to the front suspension were approved. Rule 9.1.7.C.3.p now reads “Inner bushing(s) on the front upper control arms may be replaced with offset bushings.”
“These technical rules came after a series of meetings involving experts from Mazda, NASA, and of course, the SCCA and our Club Racing Board, and we’ve come away from them moving truly in the same direction,” Lisa Noble, SCCA President/CEO, said. “Each meeting brought to light different facts, including the shortage of stock Miata heads now available, and all parties felt that this rule set is the best course of action moving forward.”