STL cylinder head porting

[Chip42]

I think tGA nailed the intent in that the SM debacle has shed light on the tech shed grey area of allowed bluepringting vs. porting. I believe the thought is that blueprinting should allow correction of lesser STOCK head castings to be as or nearly as good as the best STOCK head castings of the same part. SM allowed and specified the dimensions for this work which makes it scrutineerable. The fact that there was full on blending and porting being done and not caught for so long is another issue and has been beaten to death, but in short we need a culture change if we want our rules to be enforced. Non-spec classes have too much variety to make plunge cuts reasonably scrutineerable, and thats AFTER everyone agrees to the allowances under blueprinting in the first place, which they do not. In SM there is a huge data set from which to cull the known maximum dimensions of factory work. I doubt there's many other engines, if any, even popular ones in SCCA, where that can be said. A single example from the OEM parts counter cannot be considered as an exemplar as it will only show another sample within the supposed maximum stock dimensions, and that's assuming you can get a NIB head casting inthe first place. Don't even try to protest someone against a used part, see runoffs 2013 STU turbo miata protest.

I think the fact is that, dispite what any philosophy statement allows, the club leadership is going to spare themselves the embarassment of the 2014 SM runoffs and be far more lenient in the declared allowances for head work. BUT - they are going about it all wrong with this proposal. Step one should adding language to the blueprinting rules of the GCR Technical Glossary regarding "plunge cuts" and other casting-matching practices as "normal range" is usually not "defined by the manufacturer" in any form the club or its membership has access to. Alternatively, consider the creation of a universal allowance based on things we DO specify, CAN observe and measure objectively, or that can be determined in another defensible manner. As Len Hoffman (performance head specialist) has pointed out, it's not hard to police if you use some numbers based on valve sizes rather than allowing "blueprinting" to indeterminant stock dimensions. He's one of those expert types we would do well to consider the input of.

The problem of weight vs. expected gains isn't a problem. Due to the improvement in design, knowledge, CFD, and casting techniques over the years, more modern heads are likely to see less benefit than older ones. older ones are likely to have a greater distribution of benefit accross the sample set of castings, which isn't a big deal as those unmodified castings will have a simillar distribution under current rules. Why set a single weight penalty for the whole of the field under such a system? How do you reconcile the performance variation of differently designed heads, if we try to at all? Currently it's not considered in STL and only marginally so in IT. LP Prod has some sort of methodology to determine weights on cars but I have no idea what it is nor how well it really works. I don't see this allowance upsetting the apple cart, and in all cases except STL, it would be fixable if it were to.

In short - I'm not against the proposal's intent as I see (imagine?) it, but I'm firmly against the single class implimentation. as worded it is myopic, poorly thought through, and implies a lack of understanding of the breadth of the subject. If this is allowed, it should be allowed in a single, universally defined set of rules for all "stock" and limitted prep heads. To do otherwise will create multiple different versions of the same intended allowance, or worse, set up additional opportunities for confusion, embarrassment, etc...