Prep Differences Between SM and ITx

[Greg Amy]

This is totally legal for ITS.

...as long as they don't have any SM-compliant mods that are non-compliant to the ITCS (see above head work, rack and pinion, etc).

- GA

[ShelbyRacer]

I, too, was going to mention the head work. From my understanding, the gains certainly are a performance advantage. From working at a machine shop, I have a pretty liberal interpretation of "balance and blueprint", but that work ain't B&B.

I also was told, however, that the lack of factory specification made enforcement "unreasonably difficult", and that this allowance was specifically implemented to standardize things for purposes of simpler enforcement and equalization. Granted, that doesn't mean jack for IT compliance.

[ner88]

So, IT allows port matching and SM does not or headers for that matter.
Is the allowable head modifications a greater advantage for SM or are the IT allowances greater?
Just askin???

[Chip42]

So, IT allows port matching and SM does not or headers for that matter.
Is the allowable head modifications a greater advantage for SM or are the IT allowances greater?
Just askin???

how about "different"

It's no secret that guys are getting 125+ whp from 1.6L SMs - all that development has benefits. plug a whistler up and you get 4 cylinders with the same #, made possible by the head work. those are the ones with the head work figured out by the likes of Race Engineering/Ti/East Street/etc... IT mods "should" add up to similar gains. combine the allowances and I bet 35% over stock is realistic.

[Dano77]

how about "different".

The question isnt which makes more power, it whats different between the 2 classes. My belief was that STx would allow compliant IT cars to compete at IT weight. SM cars and IT cars have different compiance issues and weights. They arent the same.

I have no dog in either fight but its a good discussion so far.

Dan
77 IT7

[ner88]

how about "different"

It's no secret that guys are getting 125+ whp from 1.6L SMs - all that development has benefits. plug a whistler up and you get 4 cylinders with the same #, made possible by the head work. those are the ones with the head work figured out by the likes of Race Engineering/Ti/East Street/etc... IT mods "should" add up to similar gains. combine the allowances and I bet 35% over stock is realistic.

But if you combine the two the motor is not legal for either class.

My thinking is more in line with policing the class. You can't assume every SM car has the motor built to SM specs, if it is how much will it effect performance?

[mossaidis]

Still though...

- Having clarity in the differences is important.
- Having clarity on where rules are not being met is important. That is, anyone should be able to walk up to a SMx competitor and based on SM class, year and other class they are dual driving in and ask the driver which items may be "irregluar" for that class, i.e. ITx, STx, etc. from a known list. That would be nice, right?
- I would leave it to each competitor to decide if said irregularities are enough to file a protest or... simply ask the offending party to remove themselves from points or... not care.

Seems fair.

[gran racing]

I get where you're going with this Jerry and agree we don't want to turn away entries. At the same time, how a person gets to said HP does matter at least to the current GCR. Otherwise build a car much less expensively to achieve X HP than doing a full-on motor and other development work.

This is interesting and would love to see the document once done.

[Andy Bettencourt]

So, IT allows port matching and SM does not or headers for that matter.
Is the allowable head modifications a greater advantage for SM or are the IT allowances greater?
Just askin???

Much greater for IT IMHO. Remember, you can shave the head in IT to get an extra .5 point of compression. While the valve allowances in SM may be very specific, in IT it's much more grey. B&B liberties, and general engine re-freshening can include even the most basic valve job.

[Greg Amy]

Here's the very basic beginnings of a matrix, without prettiness. I'd appreciate feedback to add categories and details.

https://dl.dropboxusercontent.com/u/...STL-SM-IT.xlsx

Note this is not intended to be an all-encompassing document; it's an "at a glance" outline for competitors and scrutineers.

- GA

[Andy Bettencourt]

The question isnt which makes more power, it whats different between the 2 classes. My belief was that STx would allow compliant IT cars to compete at IT weight. SM cars and IT cars have different compiance issues and weights. They arent the same.

I have no dog in either fight but its a good discussion so far.

Dan
77 IT7

100% true...and this is why it was the right decision years ago to NOT allow SM cars, in SM prep to be automatically legal for their respective IT class. Why? The ITAC has no control over the SMAC and what future allowances they will implement in the name of parity or whatever.

At the end of the day, a full-tilt-boogie 1.6 SM will have 5-10 things done to it that are not legal for IT...but at the current time, those things do not eclipse the IT performance envelope. I would think that this would hit the ITAC's desk well before it was a bother to the STAC.

[Andy Bettencourt]

Here's the very basic beginnings of a matrix, without prettiness. I'd appreciate feedback to add categories and details.

https://dl.dropboxusercontent.com/u/...STL-SM-IT.xlsx

Note this is not intended to be an all-encompassing document; it's an "at a glance" outline for competitors and scrutineers.

- GA

I would add the .5 point of compression bump to head-work, no weight limit to wheels in IT, and maybe more clarity on the air-dam height...is the spec 3"? I thought it was bottom of the wheel so allowable height would vary depending on tire aspect ratio and size.

[Greg Amy]

I would add the .5 point of compression bump to head-work.

Doesn't that have to be within service limits?

- GA

Edit: nope, just re-read the reg: head can be 25-thou under service limit, but "under no circumstances" can be more than 1/2 point compression. Funny that we've twisted "you can shave your head but don't increase the compression more than 1/2 point!" to mean "you can increase your CR by 1/2 point but don't go any thinner than 25-thou!"

[Andy Bettencourt]

Doesn't that have to be within service limits?

- GA

Edit: nope, just re-read the reg: head can be 25-thou under service limit, but "under no circumstances" can be more than 1/2 point compression. Funny that we've twisted "you can shave your head but don't increase the compression more than 1/2 point!" to mean "you can increase your CR by 1/2 point but don't go any thinner than 25-thou!"

Correct. Still listed under the cylinder head section.

[Chip42]

The question isnt which makes more power, it whats different between the 2 classes. My belief was that STx would allow compliant IT cars to compete at IT weight. SM cars and IT cars have different compiance issues and weights. They arent the same.

I have no dog in either fight but its a good discussion so far.

the question I was answering was which set of rules makes more power..

but you are correct, they aren't the same. there ARE cars that are compliant to both SM and IT (maybe with a RP in or out) but a more full-on built to either rule set makes the car illegal for the other. determining which way a car is built and using that info to establish what weight is allowed for ST, rather than allowing an "IT like" SM to run at IT weight w/o RP is, I think, what tGA is trying to prevent.

the weights aren't hugely different though, at most ~100#s, so I worry more about an SM rules head on an IT rules short block in an IT car with IT bolt-ons making more power still and running at a weight not representative of the car (SM or IT)

[ner88]

I get where you're going with this Jerry and agree we don't want to turn away entries. At the same time, how a person gets to said HP does matter at least to the current GCR. Otherwise build a car much less expensively to achieve X HP than doing a full-on motor and other development work.

This is interesting and would love to see the document once done.

That wasn't the direction I was going...
My concern is "how do we keep it simple for tech"
Because its a SM running in IT one can't assume the head was done to SM specs, in stock form it meets all the rules...

I would also suggest it costs more to build a front running SM motor (with less HP)than an IT motor.

[gran racing]

Alright, my bad.

[Andy Bettencourt]

I would also suggest it costs more to build a front running SM motor (with less HP)than an IT motor.

No way. Balancing, blueprinting, overbore, port matching, intake and exhaust design and testing, crank scraper, oil pan baffling...

Remember, lots of the little things SM's do to maximize factory specs can also be done in IT.

[mrjones2]

Ride height - sm runs below 5"

dr / passenger vent windows?

[ShelbyRacer]

No way. Balancing, blueprinting, overbore, port matching, intake and exhaust design and testing, crank scraper, oil pan baffling...

Remember, lots of the little things SM's do to maximize factory specs can also be done in IT.

Except that all that work allows you to recon things that aren't perfect. The SM ruleset has allowances for similar levels of precision, but the process by which you get there is completely different. I consider SM to be a LOT like Showroom Stock was when there were factory teams involved. Sure, you can't "modify" the factory parts (though standard recon is allowed within limits), so you go looking for the most perfect factory parts you can find. That said, I'm making some assumptions, and I'd think that Andy would probably know the exact cost of either build better than me...

Still, that valve pocket machining allowance is a sticking point for me. I realize that one of the reasons it was done was to "allow for core shift" so that you can build a "spec" motor wiithout having to go through 50 or 500 castings looking for the best one. However, having done significant amounts of headwork in my time, that allowance, even with the "sharp edge must remain" and the "no aluminum in the bowl area or the ports may be..." clauses, there's still quite a bit of allowance beyond IT. There's certainly enough difference to make a big dent in the difference between a "stock" motor and an IT build.

Also, Andy, the way I read the SM rules, there is more than ample allowance for rudimentary balancing and blueprinting. While it may not offer all the latitude of the IT ruleset for that, I can see how it can be done to a degree that would allow for the performance that's been reported so far from SM motors on the dyno, if not even a few hp beyond that.

Oh, and I believe the 100 lb. weight difference on the 94-97 1.8L to be very significant, though I would hope that at least that would be picked up on in impound.