Yeah that makes sense. If you had head chamber volume of 10 cc (random numbers) and stroked down to pull in 90 more that's 100 total for a cr of 10 to 1 whereas if you only pulled in 70 that's 80 total making a 8 to 1. shaving the head would lower the head chamber volume. shaving down the HCV to 8 cc for example would make a cr of 12.5-1 and 10-1, respectively. Thanks for helping me grasp that. Did you see the lightbulb go on?
So you're telling me that if I worked the math right all I'd have to do is shave the head down and/or a thinner headgasket to open the gx to 10-1? Sounds too good to be true... wouldn't there be interference issues? especially if you run a cam with higher lifts. nothin higher than a 270 of course.
I was about to add that it seems there would be a trade off for cylinder fill cuz of less displacement but after thinkin about it it seems that any volume above the piston at TDC would actually hinder the pulling force of the intake stroke.
I'm gettin' excited. This make me wanna run out, grab a GTI 8v head, shave it, port an polish it and throw it back on with a copper gasket and some ARP bolts.