906 vs 452 heads on 440
Giving the choice between a 906 or a 452 head, since this is what the thread is about I'll take the 452 heads over the 906 any day of the week.
While I don't have any flow sheets I am sure the way my 452 heads are done would make a TFS head look bad. However most are not going to take an iron head to that extreme.
Tom