ITA Motor Rules

[obxr]

Hi - I recently purchased an ITA Miata. Lower end was old and I spun a bearing and need to build a new one. Just to verify my understanding of ITA rules:

I can go up to .040 over on the bore and remain in ITA.

I can't use pistons that change the CR.

I can't use aftermarket rods.

I can't use an aftermarket crank, change the stroke, etc.

The CR can only be raised a total of .5 - by any means.

Cams and valve timing must be stock.

Correct?

[mossaidis]

The CR can only be raised a total of .5 - by any means.

The only legit way to increase static CR is by overbore, usually .1 increase for every .020 overbore, and head shave.

[timo944]

The only legit way to increase static CR is by overbore, usually .1 increase for every .020 overbore, and head shave.

What about shaving the head???

[Chip42]

shaving the head within OEM allowances (as specified in the service manual for your year/make/model) is OK. head gasket must be stock compressed thickness, and CR can only go up 0.5 total as you already noted.

welcome to IT!

[Greg Amy]

Properly designed - and IT-compliant - overbore pistons will accommodate compression ratio changes via piston pin relocation. In other words, there is no allowance in the IT regs to install pistons that increase compression ratio.

The only way to increase compression and remain compliant to the IT regs is via head and block shaving, both within the factory service limits.

What most fail to understand is that the 1/2-point compression ratio increase allowance is not a performance improvement allowance, such as adding springs and shocks is. Instead, it's a recognition that when an engine is serviced within factory limits of servicing a warped head or block that there will be a resultant compression ratio change.

The fact that we racers take advantage of that service allowance to increase performance is of no concern to the letter and intent of the regs.

- Greg

[mossaidis]

The only legit way to increase static CR is by overbore, usually .1 increase for every .020 overbore, and head shave.

What about shaving the head???

see my bold words above. head shave, shaving the head... same thing.

[obxr]

I think I got it. Thanks for the replies!

[obxr]

I'm still not completely clear on connecting rods. If they are the same weight, and pivot center length, but made of better material and shaped differently - are the legal? So I'm talking about something like eagle or manley - that weighs as much as a stock rod and same length - but stronger.

[Greg Amy]

I'm still not completely clear on connecting rods. If they are the same weight, and pivot center length, but made of better material and shaped differently - are the legal? So I'm talking about something like eagle or manley - that weighs as much as a stock rod and same length - but stronger.

Nope, not allowed in Improved Touring. Stock rods only and/or exact equivalents (assuming they exist).

- GA

[quadzjr]

The only way to increase compression and remain compliant to the IT regs is via head and block shaving, both within the factory service limits.

I did not know block was allowed.. I asked about that a while ago.. and was told no.

[Greg Amy]

I did not know block was allowed.. I asked about that a while ago.. and was told no.

All parts can be serviced/repaired to factory service manual (FSM) specs. If the FSM has a service tolerance for the block, you can take advantage of that (as long as you do not exceed +0.5 CR increase.)

In fact, you can take advantage of and and all FSM specs, as long as it does not do something that is otherwise prohibited.

- GA

[Greg Amy]

This is interesting...I just pulled out the GCR and read the ITCS again...and I cannot find the verbiage allowing servicing to FSM specs. I know it was in there many moons ago - possibly a decade or more? - but now I don't see it.

Am I missing it, or did we intentionally change a basic tenet of Improved Touring?

- GA

Edit: Went back to 2004, first PDF I have, and it's not in there...

[mossaidis]

...might be considered part of "balancing and blueprinting". Some mechanics will agree doing so is part of working within FSM.

[obxr]

I would agree that block decking should be covered by "blueprinting" and servicing. As long as it meets factory specs, it would be allowed. You shouldn't have to throw a block away just because its scratched or scored and needs surfacing.

[obxr]

My new question is where exactly do you find the factory specs and/or the club established acceptable dimensions for rods? Particularly, are there any factory specs for Miata rods? I would think the following excerpts would be applicable to rods since I find no specific mention of them elsewhere:


Stock replacement parts may be obtained from sources other than the
manufacturer provided they are the exact equivalent of the original parts.
The intent of this rule is to allow the competitor to obtain replacement parts from standard industry outlets, e.g., auto-parts distributors, rather
than from the manufacturer. It is not intended to allow parts that do not
meet all dimensional and material specifications of new parts from the
manufacturer.

All engine components not otherwise listed in these rules shall
meet factory specifications for stock parts. Where factory
specifications are absent or unclear, e.g., cylinder head thick -
ness and/or combustion chamber depth, etc., the Club may
establish an acceptable dimension and/or allowable tolerance
from stock.

So where do I find the factory stock specs for rods and/or the club established acceptable dimensions and/or allowable tolerances?

If there are no specs for rods, then I would think you could use aftermarket rods - provided they are the same length and don't provide any mechanical or performance advantage - only a reliability advantage.

[Greg Amy]

My new question is where exactly do you find the factory specs and/or the club established acceptable dimensions for rods?

Factory Service Manual. That's what Tech will use to verify compliance. If it's not specified in the FSM, then the Club may choose to accept a known factory part for direct comparison.

I would think the following excerpts would be applicable to rods since I find no specific mention of them elsewhere:

Within Improved Touring, this is your overall guiding principle:

GCR 9.1.3.D: "Modifications shall not be made unless authorized herein."

You'll read folks on this board abbreviating it as IIDSYCTYC: "If It Doesn't Say You Can, Then You Can't". That means all parts must be completely stock, as delivered from the manufacturer, unless subsequent regs allow you to change it.

Said differently, the regs do not have to detail what you cannot do; IIDSYCTYC does that, IIDSYCTYC says you can't do it. From there you can read the regs to see what you CAN do.

So, bottom line, all parts must be stock parts unless otherwise allowed. It is your responsibility as the competitor to prove your parts comply with factory specs if challenged.

If there are no specs for rods, then I would think you could use aftermarket rods...

The factory provides specs for rods; it's your responsibility to discover and comply with them. And, given the over-arching IIDSYCTYC, you cannot change rods from factory specs, given there's nothing in the ITCS that allows it.

And many a person has tried the "but it's only for reliability/safety/the children" defense, and have been bounced from competition.

Remember: IIDSYCTYC.

- GA

[obxr]

Out of curiosity I read the SM rules. They do specifically allow block surfacing. Maybe that's where you read the block surfacing rule.

Looking for a copy of the FSM now

[Greg Amy]

Could be. But SM comes from a different perspective; the original SM was based on Showroom Stock rules, where you could not do ANYTHING to the engines, including balancing and blueprinting. Since then the SM regs have been bastardized to codify a lot of the cheats the engine builders were doing because where were no specs in the FSM to cover it...that's what we here call "Tech Shed Legal"...tread carefully...

[Chip42]

and just for the sake of saying it, if you ARE planning on making hidden parts illegal, know that you couldn't pick a worse platform than the miata to do so with. the car is so well known by so many that you'll be found out if cheating. it also means the speed secrets are largely already known - so follow the step by step and have a fast, legal IT car.

and you don't need to do it anyway. the oft-bandied about 125whp from a 1.6L SM motor tells me there's plenty of engineering safety factor in the bottom end of a miata to accomodate IT or SM builds.

[ShelbyRacer]

So where do I find the factory stock specs for rods and/or the club established acceptable dimensions and/or allowable tolerances?

If there are no specs for rods, then I would think you could use aftermarket rods - provided they are the same length and don't provide any mechanical or performance advantage - only a reliability advantage.

2 things-

As mentioned, you can find the factory specs for rods in a factory manual. The allowance for "aftermarket" parts was to allow a completely-equivilent-to-stock replacement, not an aftermarket "upgrade".

More importantly, you'll probably hear it said here over and over: A reliability advantage IS a performance advantage. If fact, you'll hear it so much that you'll adopt it as well, and start quoting it to others...