For what it is worth, here is my opinion. The cut and paste shown in red is from post #1 of this thread. My words are in blue
Current: 5. Unshrouding of valves is explicitly limited as follows: Seems plain and simple so far
there must be a sharp edge where the valve relief cut meets the chamber.So where the additional machining meets with the un machined surface, there must be a sharp edge. Pretty simple for me to understand, so far.
That edge must be present and unmodified. Still makes sense even if a little redundant and refers to the edge between the modified and un-modified areas of the head.
This area is not to be blended by hand, machined, or chemically processed to create a smooth transition. Again appears redundant, but still is refering to the edge between the modified and un-modified areas of the head.
The maximum dimensions are listed below, measuring guide centerline to chamber edge: Not the greatest wording, but it refers to the "flag tools" for measuring excessively large cuts
New: 5. Unshrouding of valves is explicitly limited as follows:Same as the current rule, no issue
The wall of allowed relief cut must be a single cut parallel and concentric with the valve guide for the full depth of the cut.This just adds some technical wording that keeps engine builders from angle cutting the valve reliefs. This was the original intent of the rule when it was written by the SMAc years ago
The cut must be cylindrical Round makes sense
with no taper. Here is the first issue, more on this later
The bottom of the cut must form a 90º angle With what? I am sure the rule writers mean with the "wall" of the cut. That wording needs a little cleanup. But we know what they mean.
with an allowance for a bevel or curve whose length is not to exceed .040". This is the point of contention and could also be feferred to as a taper. Some engine builders have been using a square cut tool that leaves a sharp internal corner. Others have used a tool with a rounded (insert your favorite term here;blended, radiused, etc.) tool that in theroy gives better airflow. Thus more horsepower. My interpritation of the current rule does not say if the "beveled" or "Sharp" tool is the compliant design. The current rule only addresses the edge between the modified and un-modified portions of the head. It is this intersection that is the bone of contention that is being addressed.
There must be a sharp, non-modified and non de-burred edge where the valve relief cut first meets the chamber. No part of this cut is to be blended by hand, machined, or chemically processed to create a smooth transition. Says the same as the current wording, just uses more words.
The maximum dimensions are listed below, measuring guide center line to chamber edge:Same as current wording.
So what we have is a bunch of new words that provide more detail as to what the original intent of the rule was. I don't think anyone should disagree with that.
The issue is the blending/champhering/radiusing/whatever of the intersection of the wall and the bottom of the cut. My opinion is that a radiused cut would be totally legal under the current rule. just as removing less material than that allowed would also be legal. That intersection is not specified in the current rules and any type of cut that meets the remaining rules would be legal.
My research has shown that many engine builders have used a radius of varying sizes, while others have used a sharp/square edge cut.
My opinion is that neither should be made illegal. If your engine builder feels their way is the best, let them do it that way. But let the engine builder decide for themselves. My wording would be to allow any radius as long as the wall and bottom of the cut are at a 90* angle. Thus the current tool and procedure still works. Clean up the wording and adding more detail is good. But let the engine builder do what we are all paying him for.
My biggest concern is how this was handled. It may have been done as per SCCA procedures, but definately not handled well for public opinion. This should have been part of the head gate rule clarification. But if not it should have been part of the report from the "Super Committee" on Spec Miata. It should never have become public at this point. There are too many open wounds from last years problems. We had a few weekends without drama. Now we have this. No matter if this was a personal vendetta or just a simple request for clarification, it was handled very wrong.
Honda, Toyota and the boat manufacturers had better start building their inventory, as we are trying very hard to ruin this great class.
Dave Wheeler
Advanced Autosports, the nations most complete Spec Miata shop
Author, Spec Miata Constructors Guide, version 1 and 2.0
Building Championship winning cars since 1995
4 time Central Division Spec Miata Champion car builder 2012-2013-2014-2017
Back to Back June Sprints Spec Miata 1-2 finishes 2016 and 2017
5 time June Sprints winner in Mazda's
6 Time Northern Conference Champion Car Builder
2014 SCCA Majors National point Champion car builder
2014 SCCA Runoffs winner, T4 (Bender)
2014 Central Division Champion, ITS (Wheeler)
2013 Thunderhill 25 hour winning crew chief
2007 June Sprints winner, (GT1, Mohrhauser)
Over 200 race wins and counting.
www.advanced-autosports.com
dave@advanced-autosports.com
608-313-1230