IT Piston Rules - Overbore

[Andy Bettencourt]

Originally posted by Bildon@Dec 11 2005, 09:17 PM
>> Engines may be bored to a maximum of .040 inch over

Or do you mean to say: Engines may use .040" oversized pistons?
See my Forged comment above.

>> If a .040 factory replacement piston is not offered for your car (like mine), it is not legal to have one of that size in your car.

Since we're allowing other cars to make a piston that never existed (Forged +.040) don't you think this is unfair to the guys who happen to drive a certain model that doesn't have a cast .040" overbore factory replacement?

I think we make rules too difficult at times. Can't we simplify this? All engines can go +1mm in piston diameter.

[snapback]67911[/snapback]

I am not sure what you are getting in the first comment.

We are allowing exact replica's of FPR's manufactured by a different process...nothing more, nothing less. Do I wish I thought it was legal to do a .040 set-up on my car - yup...but you can't make life equal across the board. EFI mods to cars in a class where carbed cars run? Overbores allowed in a class with rotories and no equivilant displacement increase? The list could go on and on.

We could simplify it but prepare for CREEP. See the other thread. We would be allowing additional modifications because it was EASY - and it will cost more. WHY?

AB

[Geo]

Originally posted by Bill Miller@Dec 11 2005, 04:27 PM
Careful George, If you want to restrict the group that is allowed to comment on 'original intent' to those people that wrote the rules, you've made a pretty small list, and you've closed out some of your colleagues.

[snapback]67887[/snapback]

I quite agree Bill. The only people who know the original intent are those who wrote the rule in the first place. The rest of us are speculating which is why reasonable people may disagree.

That said, it doesn't mean I'm taking sides on the rule. I'm personally on the fence.

[Geo]

Originally posted by Bildon@Dec 11 2005, 07:26 PM
Soooo just to play highjacker for fun....
Why doesnt' the rule say that you can only bore .040" over?

Afterall if I want to choose between a +.040" cast piston and a +.040" forged piston and the forged piston expands 10x more than a similar cast piston, don't I now need a .045" overbore engine?

[snapback]67900[/snapback]

Because the rule specifically states you may bore a maximum of 0.040" over. If it said you may use a piston 0.040" instead you might be right, but the bore is the specific limitation.

[Joe Harlan]

Originally posted by Geo@Dec 12 2005, 05:11 AM
Because the rule specifically states you may bore a maximum of 0.040" over. If it said you may use a piston 0.040" instead you might be right, but the bore is the specific limitation.

[snapback]67937[/snapback]

The limit must be the bore not the piston.. The bore is .040 over the maximum factory clearance. If you state .040 piston then you allow for what ever clearance people want to use. If you use a piston rule you would need to specify .040 Max at any point on the piston. This whole deal is goofy ever car has it's limits and if piston size is it for one model over another then that's the way it is. Sounds like this will be sorted at one of the early races by a checkbook to get an answer.

[Bill Miller]

Originally posted by Bildon@Dec 11 2005, 10:26 PM
Soooo just to play highjacker for fun....
Why doesnt' the rule say that you can only bore .040" over?

Afterall if I want to choose between a +.040" cast piston and a +.040" forged piston and the forged piston expands 10x more than a similar cast piston, don't I now need a .045" overbore engine?

[snapback]67900[/snapback]

I wonder if this is where the 0.0472" overbore allowance on Prod cars came from???

[Joe Harlan]

Originally posted by Bill Miller@Dec 12 2005, 09:23 AM
I wonder if this is where the 0.0472" overbore allowance on Prod cars came from???

[snapback]67978[/snapback]

Yep.....And then you start builing pistons for .0036 clearance now subtract that number from .0472 doesn't lok like much but it is. Figure out the displacement difference on you bore stroke on a VW motor with a .003 diference in bore. doesn't look like much but if your competitor has that much more displacment with all else being equal?

I just did a study on the GM 6.0 liter specs that were misprinted for T2 . It turned out by the specs that the caddys would end up with 16cc's more than the correct numbers...That again does not look like much.

[Turfer]

Originally posted by Geo@Dec 11 2005, 03:18 PM
Rick, it's not my intention to be rude, but were you part of the team that wrote the original rule? If not, how can you determine what the original intent was?

Again, this is NOT ment to be rude, but reasonable people can disagree what the original intent was because it is not stated.

[snapback]67884[/snapback]

You are right George. I don't know the original intent. No offense taken.

My honest opinion is that the original intent was to allow only factory replacement pistons offerings but then along came the allowance to order pistons to suit the need for those who wanted to max out the bore. At this point I believe the "prevailing interpretation" was to allow for all cars to go to the max .040 over bore.

Originally posted by Andy Bettencourt+Dec 11 2005, 06:45 PM-->

To me...if the wording by Rick below is approved by the CRB, it is a classic case of rules creep. CLASSIC. Having said that, I like the wording and will rely on input FROM the CRB on their thoughts before I vote.

Currently I concur with the way Darin spelled this out. If a .040 factory replacement piston is not offered for your car (like mine), it is not legal to have one of that size in your car.

AB

[snapback]67902[/snapback]

[/b]

I don't think what I propose is rules creep as much as it is clarifying. As far as rules creep that occured with the forged pistons.


<!--QuoteBegin-Andy Bettencourt@Dec 11 2005, 06:45 PM
Currently I concur with the way Darin spelled this out. If a .040 factory replacement piston is not offered for your car (like mine), it is not legal to have one of that size in your car.

AB

[snapback]67902[/snapback]

I agree with this statement. But I&#39;ll bet that there are lot of .040 over motors out there raced by people who thought they were abiding by the rule. I am for one. Luckily, I have an .020 over lump that I can freshen up next season if this wording is not revised. That may not be true for a signifcant amount of the grid.


Rick

[Andy Bettencourt]

Originally posted by Turfer@Dec 12 2005, 11:08 AM
You are right George. I don&#39;t know the original intent. No offense taken.

My honest opinion is that the original intent was to allow only factory replacement pistons offerings but then along came the allowance to order pistons to suit the need for those who wanted to max out the bore. At this point I believe the "prevailing interpretation" was to allow for all cars to go to the max .040 over bore.
I don&#39;t think what I propose is rules creep as much as it is clarifying. As far as rules creep that occured with the forged pistons.
I agree with this statement. But I&#39;ll bet that there are lot of .040 over motors out there raced by people who thought they were abiding by the rule. I am for one. Luckily, I have an .020 over lump that I can freshen up next season if this wording is not revised. That may not be true for a signifcant amount of the grid.
Rick

[snapback]67988[/snapback]

I disagree Rick. If you are &#39;clarifiying&#39; the rule (by increasing the allowance) just because people are doing it - that is creep to me. The Forged issue isn&#39;t creep IMHO but if the rules are followed, it just allows an alternate source with no performance gain.

And Rick, the rules have been the same for a while now...why would you build a .040 unit if you read the rules like we do - you must have changed your interpretation based on this thread...and that is fine too.

AB

[RSTPerformance]

Sounds like this will be sorted at one of the early races by a checkbook to get an answer.

Instead of continuing to argue (maturley I must add, as I am impressed that this has been a resonable discussion of interpretations) and instead of wasting drivers time at the first race along with the SOM&#39;s time, the Mechanics time, and everyone elses involved why don&#39;t we all pitch in 10 bucks and get at 13.9 after January 1st? We will then have a nice clarificaion good for the year!!! After that year hopefully SCCA will put something into the GCR to better clarify the rule.

I know for one that if I am on the SOM and get a protest reguarding this issue and it is clear that the protest is for clarification purposes only I will be some peo&#39;d SOM A protest is NOT the correct way to get a rule clarification. A protest IS for protesting someone that you feel has clearly broken the rules. It is far more time consuming and expensive for all parties involved, and the only way to get any sort of clarification would be through an appeal to the COA. Lets just send it off in advance and get the clarification without wasting anyones time and money.

I am in for $10 and my brother will also (If he wont give it up I will for him).

Raymond "$20 raised so far" Blethen

[Geo]

Originally posted by Joe Harlan@Dec 12 2005, 08:05 AM
The limit must be the bore not the piston.. The bore is .040 over the maximum factory clearance. If you state .040 piston then you allow for what ever clearance people want to use. If you use a piston rule you would need to specify .040 Max at any point on the piston. This whole deal is goofy ever car has it&#39;s limits and if piston size is it for one model over another then that&#39;s the way it is. Sounds like this will be sorted at one of the early races by a checkbook to get an answer.

[snapback]67965[/snapback]

Don&#39;t be too shocked Joe, but I think we are in total agreement here. The FSM specifies the largest bore for stock size. You are allowed that plus 0.040" for your bore. Use any piston diameter you like (as long as it&#39;s within the factory overbore piston spec of course).

[Joe Harlan]

Originally posted by Geo@Dec 12 2005, 02:16 PM
Don&#39;t be too shocked Joe, but I think we are in total agreement here. The FSM specifies the largest bore for stock size. You are allowed that plus 0.040" for your bore. Use any piston diameter you like (as long as it&#39;s within the factory overbore piston spec of course).

[snapback]68023[/snapback]

haha Geo, I am not shocked, Even a blind dog can catch a squirl if the squirl jumps in his mouth..... This issue really came along when the crb decided the reading of forged was OK. If you were to open up the rule to be prod and allow .047 pistons then I am gonna make pistons that will fit that bore and file rings. I throw blocks out when they worn out, Blocks like brake rotors are wear items and when they are done they are done.

[Geo]

OK, to stir the pot a bit.....

If we accept that forged pistons are OK (by decree), then this is in conflict with the rest of the piston rule regarding all other dimensions being the same as stock, at least as I understand it anyway. I don&#39;t think anyone is running forged pistons with a stock piston clearance are they?

As a result of this thought, I&#39;m more inclined to accept that the intent was to allow 0.040" overbore for all piston engine cars. Why? Because aftermarket forged pistons cannot comply with the rule as written and we already know that forged pistons have been blessed. Therefore my conclusion is that the rule as currently written is what was intended, and I&#39;d further believe that it would not be interpreted as literally as stated (just IMHO, don&#39;t build a 0.040" over and blame me if you get tossed).

[Knestis]

Originally posted by Andy Bettencourt@Dec 12 2005, 12:28 PM
... The Forged issue isn&#39;t creep IMHO but if the rules are followed, it just allows an alternate source with no performance gain. ...

The forged piston issue is EXACTLY like this one - I think.

It&#39;s my recollection that people started getting forged pistons made (perhaps when 40-over units weren&#39;t available??) before the rule change specifically allowing them was passed, and after some squawking about interpretations that "manufacturing process" wasn&#39;t a dimension controlled by the rule.

And if there&#39;s no performance advantage to be had, how come forged pistons are almost universally thought to be an improvement over cast slugs?

K

[Andy Bettencourt]

Originally posted by Knestis@Dec 12 2005, 03:41 PM


And if there&#39;s no performance advantage to be had, how come forged pistons are almost universally thought to be an improvement over cast slugs?

K

[snapback]68028[/snapback]

For the same reason forged wheels are better than cast...they are stronger and lighter. But if you make them the smae weight, they are just stronger...no?

AB

[Joe Harlan]

Originally posted by Knestis@Dec 12 2005, 02:41 PM
The forged piston issue is EXACTLY like this one - I think.



And if there&#39;s no performance advantage to be had, how come forged pistons are almost universally thought to be an improvement over cast slugs?

K

[snapback]68028[/snapback]

Hahaha......At twice the price it makes you wonder? Back to what I said before. race cars are not an investment and should not be treated as one. They are an open hole to throw money at. The next time you see somebody say..."well we changed cause everybody was already invested in it" Feel free to stick you finger right in their eye...Total BS next will be the need for .0472 over bore cause forged wears bores out quicker blah blah.

[Turfer]

Originally posted by Andy Bettencourt@Dec 12 2005, 09:28 AM
And Rick, the rules have been the same for a while now...why would you build a .040 unit if you read the rules like we do - you must have changed your interpretation based on this thread...and that is fine too.

AB

[snapback]67994[/snapback]

Your right. This thread did open my eyes to seeing the wording that is clearly there. We interpreted the rules assuming that we could go .040 over and use forged pistons. If we need to go back to the .020 over lump then so be it but I know I am not alone in this boat.

Just wondering. When the ITAC works through the different makes and models, have they been checking to see what each manufacure has on offer in the oversize piston department?

Should each car get reviewed everytime a Mfg produces the next oversize?

Rick

[Joe Harlan]

Originally posted by Turfer@Dec 12 2005, 03:48 PM
Your right. This thread did open my eyes to seeing the wording that is clearly there. We interpreted the rules assuming that we could go .040 over and use forged pistons. If we need to go back to the .020 over lump then so be it but I know I am not alone in this boat.

Just wondering. When the ITAC works through the different makes and models, have they been checking to see what each manufacure has on offer in the oversize piston department?

Should each car get reviewed everytime a Mfg produces the next oversize?

Rick

[snapback]68036[/snapback]

Basicly, I don&#39;t think the ITAC has any duty to investigate factory availabilty or options. This is one of those places that the FSM is the rule and it is not over ridden by any other rule. I think that those that can only get certain undersizes should request an option on their own spec line but I would hope even these are turned down based on a the poor precedence it would set. Complete bummer Rick but it does give you a good enduro option.

[Matt Rowe]

Originally posted by Joe Harlan@Dec 12 2005, 06:58 PM
Basicly, I don&#39;t think the ITAC has any duty to investigate factory availabilty or options.

[snapback]68037[/snapback]

I would think that the ITAC would have to know what pistons sizes were available for a given motor and factor that into the "formula" when classifying a new car. They are already estimating power gains due to IT prep and maximum legal overbore would be a factor in that so I would say the ITAC would be required to research that in order to be thorough. IF that is the way the rule is being interpreted.

Of course that level of detail is getting to be ridiculous but if the extra amount wasn&#39;t an advantage why are we arguing about this in the first place?

[Joe Harlan]

Originally posted by Matt Rowe@Dec 12 2005, 05:39 PM
I would think that the ITAC would have to know what pistons sizes were available for a given motor and factor that into the "formula" when classifying a new car. They are already estimating power gains due to IT prep and maximum legal overbore would be a factor in that so I would say the ITAC would be required to research that in order to be thorough. IF that is the way the rule is being interpreted.

Of course that level of detail is getting to be ridiculous but if the extra amount wasn&#39;t an advantage why are we arguing about this in the first place?

[snapback]68042[/snapback]

No I think you mis-understand my position. I don&#39;t believe the ITAC has any responsibilty to chase down extra sopecs or new updates to the car. I think the competitior asking for the classification better provide this kind of info when filling out the VTS sheet if they have concerns.

Matt also if you take a KA24 at a stock 89mm bore and go .020 over you get.
2415cc as opposed to a .040 coming out at 2442cc diplacement. is 27cc important? I don&#39;t know you could edge your lawn with it...(aka weedwacker)..

Broken down it&#39;s like 2 hp...In my case a one less jelly doughnut a day...

[Matt Rowe]

Joe, Okay I get what you&#39;re saying, and yes submitting that info with the VTS sheets would require the competitor do the leg work. As long as the person asking for the classification does their homework and the "formula" takes into account the maximum piston size than everything should be equal.

I&#39;d have to say 2 hp sounds about right and the average racer isn&#39;t going to notice the change. But if it&#39;s not important why are we debating it?