So........

The valve springs I just picked out are made of steel and have the same exact dimensions as the OEM springs. They happen to have twice the seat pressure. Legal? I think not.

While the manufactured part may not have a physical aspect that is as easy to measure as spring pressure, if it doesn't have all the same characteristics then it is illegal.

If the stock uprights are cast pieces then it is illegal to replace them with parts machined from billet (a solid block of material). If the stockers are steel, then it is illegal to replace them with aluminum, or, a higher grade steel.

My money is on the stockers not being billet pieces. And, if they aren't then replacing them with billet pieces is going to have someone writing some paper up over your car.

But, these are just my opinions and I'm sure other opinions will vary.
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Ron,

Your brighter than the seat pressure arguement because the pressure (rate) would be a considered fact and would be illegal because no legal part (aftermarket) shall perform an illegal function. Cast forged or billet are all processes. Processes have be proven to not be a dimension considered in this arguement (pistons) I would even go as far as to say that by opening up that rule you have also allowed alternate cranks meeting all the correct deminsions. (good intentions you know) Kinda like the old ECU rule and how it got away. I would venture to say that the parts on the S2000 are machined from forged steel parts and there for machining from a billet piece of the same grade of steel would be completely legal as hardness would not be considered in the protest. If hardness becomes an issue then I will venture to say there are a bunch of brake rotors and pistons that all the sudden become illegal parts. I hope Greg AMy chimes in on this one to show me how far off the mark I am...

Ya,all have a couple on me....