Ford Y-block cylinder head flow testing has been done by John Mummert ( & possibly by others?) on O.E. & the new aluminum heads, and been published. But have any ever been tested for "swirl or tumble"? I was reading an extensive article on cylinder head theory & mods in PHR from 2006. To keep it short, it seems that a lot of ideas used in cylinder head design & mods years ago, have proven to be ineffective or in some cases detrimental. According to the article, an indication that the porting may not be as effective as thought, was when the phrase, "the ports have been opened up" is used. Apparently this is usually a "no no!" Maintaining or improving swirl is a priority..

Paul