So Dave,

How would a competitor know in advance if they meet the compression spec? I have no idea of my compression ratio. From reading on the web, it seems that's a complicated subject, the usual advice is "to ask your engine builder" since it involves complex calculations measured when your engine is apart. Since I'm my own engine (re)builder, I asked myself and didn't get a satisfactory answer. I don't think he really knows.

Since I'm not smart enough to do anything sneaky, use stock parts and publish my builds on the net, I imagine I'm legal, but how do I really know? I would really hate to spend lots of money for a race weekend, have a PCA scruit stick a tube into my motor, declare it 10.95 and DQ me and send me home. I couldn't really put up a defense as it's all black magic to me and I imagine to a lot of other racers too.

I'm as confused as Chris, I have to say, but since I've never opened my engine I'm figuring I'm ok. I can't even read this stuff, it's so far beyond me. Not to discount the importance of it, establishing parity has always been an issue, especially in SuperCup. So, I applaud your efforts, but hey; I'm just a driver.

With a head installed on the car they take the measurement from the top of the boss on the front of head to the engine block. If you look at the factory manual there is specifications for min measurements of the boss itself. PCA has done the calculations for this and is in the rule book under sp1. When they do there measurements they use the min spec from the factory shop manual that is very liberal. However if you have an 88 engine you can not cut the head at all (except for truing). And as for "truing the head" you would not take off enough to be out of any spec for several times.
For example to get more compression you would cut of 1.4 mm to true the head you would be cutting off 5 thousands at most.

Don't kill me as I am just quoting the rules that we are trying to change. But as far as sp2 rule's go if you have any piston higher compression than stock you are illegal. All parts from the air filter to the exhaust manifold has to be "factory"

I thought they do it through the spark plug hole?
I told you I'm clueless...

I'm with Frank. I thought what PCA was talking about was using the "Whistler" which as I understand it, operates by screwing into the spark plug hole and running air past it causing a tone (the whistle), and the pitch can then determine the volume of the cylinder, and then with some other engineering magic, come up with a compression number.

So I guess the questions I have are, what method will PCA use to check/calculate the compression of the cars at the track, and how can I as a driver be sure I'm in compliance before a race event?

I'm with Cris and the good Dr as well. Would be nice to know how to verify compliance to avoid being DQ'd.

This could get complicated. And while reading, understand we are trying to establish some limits and means to limit power a car is producing. Up to this point we have used a dyno. Dynos have not be available or affordable. So what do we do as an alternative. Nothing full proof, but we do what we can do utilizing PCA techs.

We started out with set minimum limits on milling the head and the thickness of the gasket with the idea of setting limits for CRs, along with factory spec pistons. That in conjunction with using a device to measure CRs. The device would identify motors over the limit which would then be used to do further inspections for stroke, piston examining with borscope, and measuring the head. This types of limits aare set and to be used in SP1.

However, one of the difficulties in measuring a head and the gasket is one needs to know which of the four factory 944 pistons in use, as the measurement of CR will vary which in turn can change the allowed measurment of the head in producing a legal CR. This complication has led to us just going back to using a device to measure CR.

How will a driver know the exact CR their car is producing in advance of a race? Not sure other than finding a device, such as a Whistler, to take a measurement. If you are using legal pistons, legal stroke, have not milled the block, and are not using a head gasket thinner than stock,and have not milled the head beyond just truing, you will be fine. If you have done any or all of the above, you get into no man's land and you may be at risk.

Without the regular use of a dyno, we needed to come up with some type of limits to attempt to keep a level or at least defined field of play when it comes to power output.

It will be interesting to see what they come up with for checking "CR". Be it the whistler or a compression test. What's a bigger shame is that they have to do this at all. I will be at Sebring doing track support for my customers and will watch PCA very close when sp2 cars get pulled in for tech.

Just to be clear, I'm definitely ok with using an alternative to verify power compliance. My concerns are like I said, verifying my compliance (which based on what you said above, I should be good and I know my dyno numbers are good) and also how this will be done at the track. Just hoping that it's done in a manner that is relatively quick and painless so we are not in the impound area for hours on end. Post-race tech with a big field, a la Watkins Glen last year, takes forever.