Doug Kott wrote:
Steve, for the rest of us who don't know the internal squabbles of the class, what is the issue with the engine blocks?? You talk in general terms about "the issue" but don't explain it.
I know... Hard details don't seem to have emerged so, I'm a little hesitant to be the one who publicly lays it all out.
Unless this get resolved, everybody in the class is going to be claiming to have a "service block", with basically a screw you, prove it otherwise.
There are hand-stamped digits on a small section of cylinder block deck surface that is not covered by the head. These stamps "marry" the engine to the car at the final assembly factory. Service blocks (or blocks bought new from Honda parts) may not have these stamps unless it was a warranty replacement at the dealer and they happened to transfer the marks at the dealership. These marks are 10-15
TEN-thousandths of an inch deep on average and inconsistent in their depth and appearance. I saw one pair of marks on an unrebuilt factory engine, and at first we thought it was an "11". More cleaning and better light and we realized it was a "4". Then studying it further with a brighter light we saw a hint of a "6".
I heard people claim that the area in question has to be "cast". That is incorrect. The surface is a block deck. It is a machined surface from the factory. The real issue is the hand-stamped digits. Obviously a block that has been decked (the surface cut) will not have factory stamps. The lack of stamps creates a "suspicion". It is not proof in itself. If a block has been decked for a performance reason, there is an embossed square visible on the back of the block in the same general area that will be cut into. So, visually, we can easily identify a blatantly illegal decked block.
The hand-stamps were only present on five engines on the ST grid. Obviously, same issue in STL, STX, STXL, STS, and STSL.
The most likely reason for the stamps missing is that an engine has been professionally rebuilt. During that process a block deck will be cleaned with an "air pass". That is very different than "decking the block" for performance. A one thousandths pass may or may not take out the stamps. A two thousandths or three thousandths pass or, of course, multiple passes will remove the marks.
The block height on a Honda d16a6 is 212mm. That's 8.3465 or so inches. I hate metric to imperial conversions when we are talking about 5 ten-thousandths of an inch making a difference. The factory service manual does not give a service limit for decking or cleaning the block deck surface. There has been found a blueprint spec that gives a plus or minus two thousands of an inch on block height. I believe this to be the manufacturing tolerance, but its unclear at this time. It is not published as of yet, but Honda may give it to the SCCA in the future.
So, let's say a block is found. Its straight, cleans up at the correct first overbore (75.25mm) and you measure the block height on a surface plate to the ten thousandths. If it measures within two thousandths of the spec block height, its a legal block in my mind. There is no way to prove the history of the stamps. The surface is a machined surface from the factory so that isn't a give away. There were many service blocks and new blocks in existence without the stamps. There may have been factory-installed blocks that missed getting the hand-stamps. Prove to me that a mistake was NEVER made.
The ONLY thing that we can dead sure rely on now, in a protest situation, is to measure the block height since we have a spec for that. The missing numbers raise suspicion, but aren't proof. And what's worse... The existence of numbers really means nothing. Now that that item is being looked for, placing counterfeit numbers on the block could not be easier. There is nothing unique about the number stamp and it is hand-placed and hand-struck.
Now we are stuck trying to decide if motors are legal or illegal based on that 2 thousandths tolerance on the blueprint. Understand some things.... The thermal expansion of aluminum is approximately 13 microinchs per inch-degreeF. That is to say the 8.3465" tall cylinder block will expand in that plane by .0001085045 inch for each degree Fahrenheit increase in temperature (engineering types please correct me if I'm wrong--The change was far more than I was expecting). So, every ten degreesF will change your measurement by a thousandth. But obviously, reliably measuring to a thousandths on say, a valve stem, is much easier than an 8 inch tall block deck.
What about performance? What effect does a one thousandths reduction in block height have on compression ratio? For every thousandths of an inch of block height reduction, you get an increase of .018 of a compression point. We are arguing over a measurement of a thousandths of an inch across an 8.3465" height when it would take 30 thousandths decking in that particular engine to reach more than a half point increase in compression ratio. We have buried ourselves deep within the noise.
It was disturbing to hear so many people go, oh yeah, that has to be illegal... Only to find their own blocks failed the new standard. And then we find that the vast majority failed not only across this field but at the same rate at national events across the country in 2010. Like I said, its not a Jeff problem, its a class problem (or multi-class problem).
So, my official position is EVERY D16A6 engine block in the ST heirarchy is a service block that will measure atleast 211.95mm in block height unless they have the stamps in which case I suspect them of cheating .
But we know it's the RIGHT MAN 
