IT Piston Rules - Overbore
- Thread starter Banzai240
- Start date
The crux of the matter - seven pages later - still appears to be our interpretation of the original intent of the rulemakers. Chances are there's no longer any meeting minutes to see what "they" intended, so we're all trying to infer that from the written rule. The general consensus (although I disagree) is that the original intent was to use OEM pistons or their exact equivalent; if they didn't exist then you weren't allowed that overbore.
Well, let's toss another wrench in these gears.
The ITCS requires competitors to prepare their cars to manufacturer-approved procedures; to that end we're required to have copies of the service manuals, which lists all manufacturer-supported repairs, such as engine repair specs. Folks who support the above position state that we can only do what the shop manual says.
Well, if this is true - that we can only prepare to the service manual specifications - and the service manuals specify the allowable overbore sizes that the manufacturer supports, then why do you think the original ITCS rulesmakers felt compelled to reiterate that one particular shop manual specification - and simultaneously feel compelled to offer competitors other-than-OEM parts sources, something that until 2006 was never done on any other part - other than to make that .040" overbore allowance available to all vehicles, not just those with that offer 40-thou overbore from the manufacturer...? - GA
Well, let's toss another wrench in these gears.
The ITCS requires competitors to prepare their cars to manufacturer-approved procedures; to that end we're required to have copies of the service manuals, which lists all manufacturer-supported repairs, such as engine repair specs. Folks who support the above position state that we can only do what the shop manual says.
Well, if this is true - that we can only prepare to the service manual specifications - and the service manuals specify the allowable overbore sizes that the manufacturer supports, then why do you think the original ITCS rulesmakers felt compelled to reiterate that one particular shop manual specification - and simultaneously feel compelled to offer competitors other-than-OEM parts sources, something that until 2006 was never done on any other part - other than to make that .040" overbore allowance available to all vehicles, not just those with that offer 40-thou overbore from the manufacturer...? - GA
Andy Bettencourt
Super Moderator
Because the "up to .040" is that max allowed FRP that can be used. Someone like Dodge would write an addendum to thier FSM for .080 or something crazy for their IT support program. The max has been established and the individual parameters are defined car-by-car.
The forged issue again, is one that has to do with the method of manufacture of the FRP - not an allowance to go to the max where a FRP doesn't exist.
AB
So that's Kirk, Greg, and Rick who are willing to admit that their LONG-held understanding of that rule goes counter to the literal re-reading. I think there are a lot more out there. Full credit to Darin for unearthing this issue but man, what a stinker this one is...
K
EDIT - It's fun how people who truly believe that the original intent of Our Forefathers did not include having +.040 pistons whizzed out of forged blanks where no OE parts were available, are putting so much stock in the apparent precision of wording in this particular rule. Since NONE of us were actually in that meeting, we are all forced to make inferences - assuming that the original intent matters. I think it does but I have less faith in the specific words of the old testament (the c.1985 ITCS) than I do in the prevailing spirit behind them. I WAS there for that.
Anyone else wonder how the US Supreme Court deals with this kind of stuff all day long? :119:
Nah, I don't buy it, Andy. If that were true, then why not list a whole lotta other FSM specs that the manufacturer could "cheat up" to give their cars a performance boost? Why just the bore size? Besides, 40-thou overbore has pretty much been the auto industry standard for max service limits for, oh, 'bout a hundred years or so; you'd be hard-pressed to find any FSM that lists anything bigger (ain't sayin' it doesn't exist, but I don't think so...hell, prove me wrong.)
Plus, if we take your position, it still does not explain why all the details on pistons were listed. If you're correct, and the rule was simply "...maximum of .040 inch over standard bore size" then that's that; there would be nothing to allow anything but factory oversize pistons (i.e., no provisions for aftermarket pistons).
So, riddle me that Batman: if you're correct, that this was written as an upper limit only, then why go into all the details of the pistons and offer the use of aftermarket parts where it never was before? The explanation for that is simple: to offer that .040" overbore to all competititors, even if the factory did not. There is no other logical explanation.
"Forged pistons" are a recent development in IT and a red herring to the topic at hand. The overbore pistons rule has been there from the very beginning in 1984, and it's only now, 21+ years later, that this historical "revision" (reversion?) of the rules has come about.
Kirk's right, this one's a stinker, and I think y'all "literal" boys are the ones way out there reading the scoreboard from underneath... - GA
Andy Bettencourt
Super Moderator
Maybe the GCR has 'evolved' to it's current wording? Can someone produce a GCR from previous years that shows something different? If not, I don't see how the intent that you guys (who I believe are trustworthy) remember to be so, could have been lost in translation.
I, too, find it amusing that people argue the literal side of the rules (and ignore the obvious intent) to gain advantages but in this case the word is thrown out because someone remembers the original intent as something different.
I have no issue changing the wording per Rick's post. The big thing right now on my mind is that there are builders building cars with .040 lightweight, forged pistons. Thier stance? No FRP exists to reference a 'exacting' spec, so they are using it as 'open' season. (These are guys who I believe, believe in their stance and would not knowingly cheat, even though I don't think it's legal) The hole in the rule now if you want it your way, is that you must state that the minimum weight of any non-factory replacement piston must be no lighter than a stock unit.
Greg, you have done some time on some protest committees...you see any way someone wins if I protest a .040 motor when no FRP exist? I don't. We either need to agree or we need to clarifiy the rule...right?
AB
I used to have an '84 ITCS (the category spec books used to all come separate from the GCR and you had to buy each one that you wanted). Unfortunately, it appears I lost those in a move some time ago. The oldest I have on hand is 1995; in that book ITCS 17.1.4.D.1.j is exactly the same as in the 2005 GCR, except the words "Cast or forged..." have been added in front of "...equivalent pistons shall provide the same dome...". Further, there are no "revision bars" in the margins, so the rule has been there since at least 1994.
From experience I can tell you I am extremely confident the rule has been the same for the 10 years prior to that.
Andy, if someone protested you for having 40-thou overbore pistons in your Miata where the factory never offered them, and those pistons were exact equivalents of a factory standard piston in every way described in ITCS 17.1.4.D.1.j except for bore, and that bore size was within +.040" of a factory maximum standard bore size, in my opinion you would pass as legal. Would the protester win on appeal using the literal interpretation of the rule? I'd suggest that's highly unlikely.
However, if you tried to pass off the "no FRP exists to reference a 'exacting' spec, so it's 'open' season" I'd bust you as being contrary to the regulations. And that's just common sense. Could you win on appeal? I guess that depends on the sense of humor of the appeals board, but I suggest not. - GA
From experience I can tell you I am extremely confident the rule has been the same for the 10 years prior to that.
Andy, if someone protested you for having 40-thou overbore pistons in your Miata where the factory never offered them, and those pistons were exact equivalents of a factory standard piston in every way described in ITCS 17.1.4.D.1.j except for bore, and that bore size was within +.040" of a factory maximum standard bore size, in my opinion you would pass as legal. Would the protester win on appeal using the literal interpretation of the rule? I'd suggest that's highly unlikely.
However, if you tried to pass off the "no FRP exists to reference a 'exacting' spec, so it's 'open' season" I'd bust you as being contrary to the regulations. And that's just common sense. Could you win on appeal? I guess that depends on the sense of humor of the appeals board, but I suggest not. - GA
Are you sure Joe? No responsiblity whatsoever even though they are currently leading the charge to update and realign IT into the future. It is work that needs to be done for sure but wouldn't they want to go by the maximum potential that a vehicle can produce? I suspect that they have been operating to a max .040 over engine when working through the list of cars and somehow during all this Darin stumbled over the rule and here we are.
The K series engine is still quite new. I haven't researched this but there might not yet be a FRP available to the public. .020 = 2Hp, .040 = 4Hp. It is not a lot but would cetainly make a difference.
Rick
If by "lightweight," you mean "lighter than the original, stock diameter" then please don't include me in that list.
I have always presumed that the specification of dimensions - including weight - meant that aftermarket pistons, including oversize replacements, whether cast or forged could be no lighter than the stock parts.
Lumping those of us who believed THIS in good faith with those of the "open season" ilk isn't fair.
K
Joe Harlan
New member
. I think the last part wins both protests
Joe Harlan
New member
completely different argument. Again you scew the argument. The issue was the difference between 020 and .040.... So if your getting a car that has not oversized listed in the FSM I wouldn't build it.
As far as the stumbling across the rule it is a proper reading of the rule and because some people got caught with it does not make the reading wrong. I have been through 8 factory manuals tonite and all of them list up to a .040....Anyone ever consider maybe there is a reason that some manufactures don't offer a .040 piston? Maybe it was felt their cylinder liners couldn't handle it. I know on the early Datsun stuff they recommended sonic testing when going to .040 on some stuff.
I'll bet that the FRP pistons or the specs of the same are not available for half of those manuals you thumbed through.
So, you are saying that the only cars that should be built are the ones that have the .040 over FRP available because all the ones that don't offer it have been overrated when classified.
Are you being genuine in this debate?
Rick
Joe Harlan
New member
Rick, I am abosolutely being genuine. I have the books on the shelf. Now as a guy that is intent on building legal engines the answer is this. For every type of engine I build for IT mostly Nissan I have a parts shelf with a factory .040 or .020 piston on the shelf as a sample for what ever after market pistons we may use. When the engine goes to the balance shop the stock OE piston goes as the minimum weight sample to balance to. So yes I am that anal about reading the rules. In a protest you better have a way to prove your case or somebody will prove it for you. That is why I charge money to build them cause they are fast and legal. I amsure I am not the only one that goes that far. PS I also have a stock rod for every motor I have in service also. A factory service manual should list every overbore size the factory lists pistons for includeing clearances. Sorry you got dinged in the readin of the rules but that doesn't make the rule wrong.
I am being genuine in saying that if an over bore piston is not listed for a motor I wouldn't build it without clarification. And the following is what I was directly refering to.
What are you saying here. If they show a piston and don't sell it?
Joe, that's your interpretation of the rule; we all read it the same way.
Please don't hold yourself out as "The One Who Knows", because if taken in context of the history of this category, a history that many of us have been a part of since its inception, you'd be wrong. We were there when the category was first introduced, and we - better than you - understand the historical context of these rules. If, by some chance, you were there in 1984 and had the same position you do now, you were being looked at quizzically.
If you continue to hold this position, Joe, I invite you to answer the questions I posted above; those have yet to be satisafactorily addressed (although I admire Andy's thought process).
That's pretty arrogant, don't you think? Surely you're not claiming to be the only one building legal engines? Or, are you claiming that unless someone keeps a piston on the shelf for comparison - a part that, by the way, would be inadmissable in a protest situation - that someone cannot build legal engines?
Bully for you, man, good job. You get the IT Rules Nerd Medal of "Special" Notation.
- GA
You forgot me Kirk.
I believe there conflict within the rule as written. To my knowledge it's impossible to use forged pistons and comply with the rule requiring the piston to be of stock dimensions since forged pistons require greater clearance. They cannot be the same diameter as a stock piston. So, as long as we are accepting deviations, I'm more than willing to accept the deviation of allowing 0.040" overbore for all. If we didn't accept forged pistons I might fall in the literalist category.
I suppose one could argue that you build the forged piston to stock dimension and bore to proper clearance (thus effectively disallowing any forged 0.040" pistons), but I think that is far too great a stretch.
Bill Miller
New member
Add me to that list.
Andy Bettencourt
Super Moderator
Kirk,
I am not sure how you inferred that I lumped you in with the group I singled out. I didn't mean to if that is the way it came off in text. I actually thought I did the opposite. WHat I should have said was a 'group of pro engine builders'
AB
Andy Bettencourt
Super Moderator
I am taking this on for clarification. If I have to pony up the money, I will.
Even if I read the rule like the 'fab-five', I would still go with my FRP at .020. Mazdacomp sells them for $40 each...and the custom .040 would be big $. I have a lot better things to spend that $600 on than 2 hp and no option to rebuild.
AB
Even if I read the rule like the 'fab-five', I would still go with my FRP at .020. Mazdacomp sells them for $40 each...and the custom .040 would be big $. I have a lot better things to spend that $600 on than 2 hp and no option to rebuild.
AB