I dont ever hear of alot of peeps running these...like the 290's....and 063's. My compression is way low....have always wondered what taking away 18 cc's out of the combustion chamber...would do for me. Am I an idiot to think these heads may be an improvement over the alum. brodix bb2+ heads I have now. My 557 is only 8.4 to 1.....was orig. assembled for some boost.(cept the cam grind...knew I couldnt do it all at once). Right now I pull my AA cut to 4900-5kish would like to see 5k plus. More than anything...was curious why these are never used. I hear how the closed chamber ford heads can support a higher compression ratio/more ping resistant than an open chamber chev head.