IT Piston Rules - Overbore
- Thread starter Banzai240
- Start date
Andy Bettencourt
Super Moderator
For the record, I do not think Greg would build an illegal motor, nor do I even know if he has .040 slugs - or if Nissan offered 40's for his car. IMHO, he and I have been debating the letter / intent / application of this rule without a dirct link to his car, or anyones car - except the occasional reference to mine as an example.
In addition, I also believe he would spend the EXTRA money to be legal if he had too.
AB
Andy Bettencourt
Super Moderator
Originally posted by ddewhurst@Dec 13 2005, 06:31 PM
***Maybe the real answer is that I am f-ing crazy. Crap.***
Andy, you'll get back to normal after the ITAC term is over.
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Bildon
New member
hmmmmm so I wonder what was lightened on the other end to keep the whole thing in balance, critical at 6000 RPM. Big ends of the rods or crank throws? So after the heavier pistons were put back in
then you also replaced the crank and/or rods that you have lighted by 25g each as they were now TOO light to be "only enough to balance" legal ????? 
sorry to dissapoint you, Bill, and sad you implied I was cheating.
Inline pistons (and boxers) have no need to be have a weight adjustment to any other parts except the other pistons. Only V type engines require complex balancing. Please don't impune my integrity.
ps: the motor wasn't even balanced. I've never balanced any of my IT motors, or ground the cranks-and in my Volvo motors, even replaced an old oilpump.
I've been doing this since 1968 and have built a few motors; I know what's important and what's not. (factory VW/Volvo stuff is very well balanced from the factory) Rings that seal are important. Legally removing 100 grams (nearly 4 oz) of weight from pistons is a signifigant improvement in acceleration and would be dumb not to do. I think some people thought that if some bozzo arrived at the track towing a camper with a 4 door Volvo and won, then he must be cheating. I don't think a lot of peple realized the thought and preparation I brought to the table. I didn't get bore concentricty good enough til my 3rd iteration honing plate!
Phil
Inline pistons (and boxers) have no need to be have a weight adjustment to any other parts except the other pistons. Only V type engines require complex balancing. Please don't impune my integrity.
ps: the motor wasn't even balanced. I've never balanced any of my IT motors, or ground the cranks-and in my Volvo motors, even replaced an old oilpump.
I've been doing this since 1968 and have built a few motors; I know what's important and what's not. (factory VW/Volvo stuff is very well balanced from the factory) Rings that seal are important. Legally removing 100 grams (nearly 4 oz) of weight from pistons is a signifigant improvement in acceleration and would be dumb not to do. I think some people thought that if some bozzo arrived at the track towing a camper with a 4 door Volvo and won, then he must be cheating. I don't think a lot of peple realized the thought and preparation I brought to the table. I didn't get bore concentricty good enough til my 3rd iteration honing plate!
Phil
Joe Harlan
New member
Phil, You would be welcome in the shop also. My made a comment that looked like you were calling the ITAC bones heads....Had you been saying i was a bone head I wouldn't have even concerned myself...Now to the subject in bold there is nothing contrieved in the reading of the rule, It is there in plain ink. You by your own admission say you were wrong once. No chance you could see where you could be wrong today? The interesting part would be to know how many cars this really effects. DOes the volvo not have .040 pistons in the FSM?
Bildon
New member
>> sorry to dissapoint you, Bill, and sad you implied I was cheating.
Aww come on! I wasn't implying intentional cheating. I just though you caught yourself in a conundrum, since I never assumed that anyone who would have lighter forged pistons made would also ignore balancing the engine. But I stand corrected! 
>> I've never balanced any of my IT motors
Give it a whirl. Your 2nd and 3rd order vibrations will hate you for it.
Aww come on!
I wasn't implying intentional cheating. I just though you caught yourself in a conundrum, since I never assumed that anyone who would have lighter forged pistons made would also ignore balancing the engine. But I stand corrected! >> I've never balanced any of my IT motors
Give it a whirl. Your 2nd and 3rd order vibrations will hate you for it.
Okay - mental experiment. If the rule had said this since its inception...
Engines may be bored to a maximum of .040 inch over standard bore size. Cast or forged equivalent pistons shall provide the same dome/dish/valve relief configuration, ring thickness and spacing, pin height relationship, weight, and compression ratio as factory replacement oversize pistons. Piston rings are unrestricted.
...would there be an issue?
K
Engines may be bored to a maximum of .040 inch over standard bore size. Cast or forged equivalent pistons shall provide the same dome/dish/valve relief configuration, ring thickness and spacing, pin height relationship, weight, and compression ratio as factory replacement oversize pistons. Piston rings are unrestricted.
...would there be an issue?
K
Bill Miller
New member
Looks good Kirk, the only thing I would add would be the following:
In the event that factory oversize pistons are not available, no replacement piston shall weigh less than a factory standard bore piston. In addition, any replacement piston shall provide the same dome/dish/valve relief configuration, ring thickness and spacing, pin height relationship, weight, and compression ratio as factory standard bore pistons.
I know that a 040 over piston will weigh more than a standard bore piston, but is it really going to be that significant an amount? Also, this is only allowed in the case where no factory oversized pistons are available.
In the event that factory oversize pistons are not available, no replacement piston shall weigh less than a factory standard bore piston. In addition, any replacement piston shall provide the same dome/dish/valve relief configuration, ring thickness and spacing, pin height relationship, weight, and compression ratio as factory standard bore pistons.
I know that a 040 over piston will weigh more than a standard bore piston, but is it really going to be that significant an amount? Also, this is only allowed in the case where no factory oversized pistons are available.
Joe-I wasn't wrong at all to have light pistons made-they were legal for a year.
And the club wansn't wrong or boneheaded to clean up the wording of the rule and eliminate the loophole.
I think it would be wrong and boneheaded to create a ruling that would make a lot of well intentioned and reasonable people illegal and cause them a lot of uneeded expense.
I don't know if the 140 workshop manual lists any oversizes-I sold it with the car 10 years ago when I got paralyzed.
The Bently A2 manual only lists .25 and ,50 pistons.
1.0 pistons are readily available from oe manufacturers (Kolbenschmidt. et al) and were recently advertised by Bildon. They are identical to originals in every way except diameter and weight (ie: a couple grams heavy). Would all you cheater
VW guys please raise your hands? OK then-now go throw away your engine and do over. Forget about tires-do something you really needed to do.
And the club wansn't wrong or boneheaded to clean up the wording of the rule and eliminate the loophole.
I think it would be wrong and boneheaded to create a ruling that would make a lot of well intentioned and reasonable people illegal and cause them a lot of uneeded expense.
I don't know if the 140 workshop manual lists any oversizes-I sold it with the car 10 years ago when I got paralyzed.
The Bently A2 manual only lists .25 and ,50 pistons.
1.0 pistons are readily available from oe manufacturers (Kolbenschmidt. et al) and were recently advertised by Bildon. They are identical to originals in every way except diameter and weight (ie: a couple grams heavy). Would all you cheater
VW guys please raise your hands? OK then-now go throw away your engine and do over. Forget about tires-do something you really needed to do.
Andy Bettencourt
Super Moderator
Is it possible for a forged piston to weigh the same as a cast unit if all the other specs are equal? Are they not inherently lighter by design?
Joe Harlan
New member
Phil, I guess this is the only place we aren't going to agree. If the reading of the rule is that an FSM optioned piston size is the limit then it makes no difference to me that people had good intentions. Good intentions don't make you legal and shouldn't be considered and wouldn't be considered in a protest. If you gonna have rules then they have to be followed. You won't see me get all wacked about a washer bottle but internal engine parts make a difference.
Bill Miller
New member
Phil,
The SCCA has made rule changes that have cost people a lot of money before. The ones that jump immediately to mind were the RR 3x adjustable shocks and engine coatings. At least w/ the shocks, you had a chance of getting some of your money back when you sold them. Don't think there was much of a market, outside of racing, for coated engine blocks. And maybe you'd like to speak w/ Derek Ketchie about a recent example.
I really hate it when people trot out the "don't change the rule, it will cost people money" excuse. It's got to be one of the root causes of rules creep.
The SCCA has made rule changes that have cost people a lot of money before. The ones that jump immediately to mind were the RR 3x adjustable shocks and engine coatings. At least w/ the shocks, you had a chance of getting some of your money back when you sold them. Don't think there was much of a market, outside of racing, for coated engine blocks. And maybe you'd like to speak w/ Derek Ketchie about a recent example.
I really hate it when people trot out the "don't change the rule, it will cost people money" excuse. It's got to be one of the root causes of rules creep.
Andy-my super-light pistons were 25g light because they had tapered pins and a lot less material in them. They fully met the rule for legality in 1987.
I expect identical forgings to weigh almost exactly the same as cast. As the name implies, cast pistons are cast and forged pistons are struck with a die, kinda like minting coins. You can always detemine a piston NOT to be a forging if there is any overhanging material in the underside that was not created by machining it, ie: in the pin boss area between the pin and the crown (impossible to create with a die). Now I'm wondering if there are any identical forgings. Whatever-the real advantage of forged in a full-blown race engine is that they are much stronger than cast. There is no need for them in the lightly stressed apps of a mildly modded, relatively low compression IT motor. Why did I use them? Because the only way to get to my (legal then!) endpoint was to have them custom made from Chevy forged blanks. A lightened flywheel would have been more effective and much cheaper but not legal.
Phil
ps Joe-my point about the reading of the rule: It's pretty clear to me that the rule can be reasonably read 2 ways. And that given the genesis of the rule, old timers have always been steered to the "40 all" interpretation, And given that taking the opposite view would be uneccesarily burdensome to many honest hard working members, then why not compromise? What I think would be best would be to outlaw ANY oversized piston. Really. It would be so much cheaper. It would be so much simpler. No honing plates needed! A Golf engine, you could build in the car (rings, rods, mains). At 81mm bore, every +.020=1.25% addtl displacement, so +020 yields 1.5hp, +040: 3 hp. (ITB Golf: 100hp at the wheels) So we're arguing about 1.25% increase. Honestly, do you really belive this is significant? Its less than the kind of error you see in serial pulls on a good engine dyno (maybe you even said this earlier, someone did). I'd trade inlet air temp 10F lower for 40 over any day of the week and so would you!
I expect identical forgings to weigh almost exactly the same as cast. As the name implies, cast pistons are cast and forged pistons are struck with a die, kinda like minting coins. You can always detemine a piston NOT to be a forging if there is any overhanging material in the underside that was not created by machining it, ie: in the pin boss area between the pin and the crown (impossible to create with a die). Now I'm wondering if there are any identical forgings. Whatever-the real advantage of forged in a full-blown race engine is that they are much stronger than cast. There is no need for them in the lightly stressed apps of a mildly modded, relatively low compression IT motor. Why did I use them? Because the only way to get to my (legal then!) endpoint was to have them custom made from Chevy forged blanks. A lightened flywheel would have been more effective and much cheaper but not legal.
Phil
ps Joe-my point about the reading of the rule: It's pretty clear to me that the rule can be reasonably read 2 ways. And that given the genesis of the rule, old timers have always been steered to the "40 all" interpretation, And given that taking the opposite view would be uneccesarily burdensome to many honest hard working members, then why not compromise? What I think would be best would be to outlaw ANY oversized piston. Really. It would be so much cheaper. It would be so much simpler. No honing plates needed! A Golf engine, you could build in the car (rings, rods, mains). At 81mm bore, every +.020=1.25% addtl displacement, so +020 yields 1.5hp, +040: 3 hp. (ITB Golf: 100hp at the wheels) So we're arguing about 1.25% increase. Honestly, do you really belive this is significant? Its less than the kind of error you see in serial pulls on a good engine dyno (maybe you even said this earlier, someone did). I'd trade inlet air temp 10F lower for 40 over any day of the week and so would you!
Bildon
New member
Andy. Yes, they're going to be lighter. Unless you spend a rediculous amount of money designing a set that are heavier than needed.
Phil !!!!
You just let the cat out of the bag. :119:
>> The Bently A2 manual only lists .25 and ,50 pistons.
The ETKA also shows only .25 nad .50 oversized as factory numbers for all Golf / Jetta engines, Golf 2, Golf 3 and 4 !
That pretty much makes most VWs in the country that are fully built illegal by some recent interpretations here.
So this illustrates my earlier point. Please just write the rule so that anyone can put .040 pistons in their car and be done with it!
:angry: <cynical rant follows> Or keep nit picking, keep pigeon holeing, keep arguing, and most importantly KEEP making the rules more and more exclusive so that IT becomes more of a pain to enter into!
Edit: After reading Phil's quote above that slipped in as I was typing...
>> What I think would be best would be to outlaw ANY oversized piston.
Yup, I would agree. Except that you'd have a lot of people pissed off now. Perhaps make that an '08 rule ?
Phil !!!!
You just let the cat out of the bag. :119:
>> The Bently A2 manual only lists .25 and ,50 pistons.
The ETKA also shows only .25 nad .50 oversized as factory numbers for all Golf / Jetta engines, Golf 2, Golf 3 and 4 !
That pretty much makes most VWs in the country that are fully built illegal by some recent interpretations here.
So this illustrates my earlier point. Please just write the rule so that anyone can put .040 pistons in their car and be done with it!
:angry: <cynical rant follows> Or keep nit picking, keep pigeon holeing, keep arguing, and most importantly KEEP making the rules more and more exclusive so that IT becomes more of a pain to enter into!
Edit: After reading Phil's quote above that slipped in as I was typing...
>> What I think would be best would be to outlaw ANY oversized piston.
Yup, I would agree. Except that you'd have a lot of people pissed off now. Perhaps make that an '08 rule ?
Bill Miller-yes! the club sure has made rules changes that pissed people off. They've also been trying to be user friendly. My stand is that given that it's been generally accepted that +040 was the standard for all for 20yrs (until this string, I never heard this new interpretation or imagined it), that they would be disinclined to "clarify" the rule in a way that would really hurt a lot of consumers while "fixing" something thats not broke.
RIGHT ON BILL S!!
and yeah-I have EKTA also; I just didn't want to be TOO honest. But you know something? I'd bet that somewhere in the world, VW factory rebuilt engines are available with those very same 040 pistons. In the aircooled days, factory rebuilt engines had all kinds of factory oversize/undersize VW OE parts that were unavailable in the parts dept/non in parts catalog. (like +030" 1700 Bus pistons)
RIGHT ON BILL S!!
and yeah-I have EKTA also; I just didn't want to be TOO honest. But you know something? I'd bet that somewhere in the world, VW factory rebuilt engines are available with those very same 040 pistons. In the aircooled days, factory rebuilt engines had all kinds of factory oversize/undersize VW OE parts that were unavailable in the parts dept/non in parts catalog. (like +030" 1700 Bus pistons)
Joe Harlan
New member
Phil, I agree we are not talking alot of HP, But 3HP in spec Miata would likely be the difference between 1 st and 5th. The was a time in ITS that we would kill for 3 HP in a Z motor.....Please don't lump all old timers in the.040 crowd. Stuff happens all the time in racing that is wrong. I find a lot of time it is monkey see monkey do. That's were we get good people caught in a rules issue. The problem with just saying "well so many have all ready done it" is this. once it's accepted you can't put the genie back. I don't believe based on "intent" bleh that the original writers of the ITCS ever thought you would have to stuff a Motec in a ECU to be competitive. Said ECU costs as much as a decent ITC car. Now once 4 or 5 people bought them the will to put them back was not there. So again if the rule is mis-read by me then you'all are OK and shame on me for leaving 3 HP on the table. But i the rule is mis-read by the old guard then shame them for leading us all down this path.
Joe Harlan
New member
Originally posted by Bildon@Dec 14 2005, 09:32 AM
>> once it's accepted you can't put the genie back.
hmm, I thought it has been accepted for many many years.
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And I thought you had to provide proof of the legality of a part....
