Piston Rule

[PSherm]

Section 9.1.3.D.1.j states "Factory replacement ppistons or their equivalent with the exception of diameter shall be used. Cast or forged equivalent pistons shall provide blah, blah, blah..."

If the factory piston in my car are cast, does that mean my replacement "equivalent" pistons shall be cast or does that mean my replacement "equivalent" pistons may be cast or forged?

Every time I read my GCR, I swear it was written by politicians...

[Andy Bettencourt]

A forged piston may be used provided it is exactly the same 'dimensionally' as a stock piston. So to use my car as an example:

I have Mazda OEM factory replacement .020 over pistons. They are cast. If I wanted to go forged, they would have to be the exact same to be legal. Forging is just the method of manufacture. They need to meet all specs - ESPECIALLY WEIGHT - as stated in the rules.

Mazda doesn't make a .040 over piston. So if I was to go .040, I would have to source the stuff with all the right specs - and be no lighter than the factory standard bore piston per the rules.

Bottom line, the pistons need to provide all the same dimensions (except the increase in size obviously) as the stockers - and nothing can be lighter than the standard bore/factory OEM units or the factory overbore units.

[johnny yanez]

hmmmm but, if i use .040 over piston and since mazda does not have them, how can i get the duplicate weight>>?? since i would think they would be heavier. bigger piston and all,,,,,, ??? or can i get make them as light as the standard OEM piston that i took out of the car ??

[Greg Amy]

Here we go again...


(I STRONGLY suggest using the search function. Reason is, this was a SERIOUSLY contentious debate on this very forum not more than 6-8 months ago...I don't think any of us really want to go through this again...)

[Andy Bettencourt]

hmmmm but, if i use .040 over piston and since mazda does not have them, how can i get the duplicate weight>>?? since i would think they would be heavier. bigger piston and all,,,,,, ??? or can i get make them as light as the standard OEM piston that i took out of the car ??

[/b]

That answer is specifically called out in the 2007 rule.

[planet6racing]

Here we go again...
(I STRONGLY suggest using the search function. Reason is, this was a SERIOUSLY contentious debate on this very forum not more than 6-8 months ago...I don't think any of us really want to go through this again...)
[/b]

I couldn't agree more...

[GKR_17]

Bottom line, the pistons need to provide all the same dimensions (except the increase in size obviously) as the stockers - and nothing can be lighter than the standard bore/factory OEM units <strike>or the factory overbore units.</strike>
[/b]

[Greg Amy]

This argument last year was extremely ugly, resulted in a rule change.
I&#39;ll leave you with a link to that prior topic:

http://itforum.improvedtouring.com/forums/...?showtopic=6652

...and a verbatim quote from the new 2007 GCR (ITCS 9.1.3.j):

"Engines may be bored to a maximum of .040 inch over standard bore size. Factory replacement pistons or their equivalent with the exception of diameter shall be used. Cast or forged equivalent pistons shall provide the same dome/dish/valve relief configuration, ring groove width and spacing, pin height relationship, weigh no less than the factory standard bore pistons. Piston rings are unrestricted."

[Andy Bettencourt]

OK, since there IS new wording in the GCR, I wanted to see if it&#39;s actually effective. A question from the last thread got some panties in a wad because the debate last year reallt did define for a lot of us how people torthure the rules to suit themselves.

Engines may be bored to a maximum of .040 inch over standard bore size. Factory replacement pistons or their equivalent with the exception of diameter shall be used. Cast or forged equivalent pistons shall provide the same dome/dish/valve relief configuration, ring groove width and spacing, pin height relationship, weigh no less than the factory standard bore pistons. Piston rings are unrestricted.

Here is how the new rule should apply:

- Up to a .040 overbore is allowed
- If overbore pistons are used, they shall be factory replacements or their exact equivalent, including weight
- Those exact equivalents can be of cast manufacture or forged manufacture
- If you overbore to a spec where there is no factory overbore piston, then your piston specs must be the same as stock, with the obvious exception of diameter
- Factory replacement pistons must weigh what they weigh
- Equivalent pistons must weigh NO LESS than the OEM standard bore pistons

It&#39;s all in the rule. Is this how people read it or have I looked at it one too many times to have a clear view of what it actually says?

[JoshS]

It&#39;s all in the rule. Is this how people read it or have I looked at it one too many times to have a clear view of what it actually says?
[/b]

Well, I&#39;m new to the rule, but that&#39;s what I think it says.

[johnny yanez]

THANKS ANDY AND AMY for your time and patience , im sure it clarified alot of questions, and as you said its in the rule book, just have read it a bit closer and slowly, thanks again