What /6 is Best For Forced Induction 170, 198, or 225?

Is there a max rpm that is a general guideline for these engines, that the bottom end really doesn't like to go above?

Around what RPM does the 225, 198, 170 run out of airflow with a ported head?


I just pulled up allpar site on the /6 its interesting to see how the rpm drops for peak horsepower going down the list.

Engine......Years.............C/R...............Horsepower...........Torque
170........1959-1963.......8.2 to 1.........101 @ 4400...........155@ 2400
170........1964-1966.......8.5 to 1.........101 @ 4400...........155 @ 2400
170........1967-1969.......8.5 to 1.........115 @ 4400...........155 @ 2400
198........1970-1971.......8.4 to 1.........125 @ 4400...........180 @ 2000
198........1972...............8.4 to 1.........100 @ 4400...........160 @ 2400
198........1973...............8.4 to 1...........95 @ 4000...........150 @ 1600
198........1974...............8.4 to 1...........95 @ 4000...........145 @ 2000
225........1960-1962.......8.5 to 1.........145 @ 4000...........215 @ 2800
225........1963...............8.2 to 1.........145 @ 4000...........215 @ 2400
225........1964-1971.......8.4 to 1.........145 @ 4000...........215 @ 2400
225........1972...............8.4 to 1.........110 @ 4000...........185 @ 2000
225........1973...............8.4 to 1.........105 @ 4000...........185 @ 1600
225........1974...............8.4 to 1..........105 @ 3600...........180 @ 1600
225........1975...............8.4 to 1............95 @ 3600...........170 @ 1600
225........1976-78..........8.4 to 1...........100 @ 3600...........170 @ 1600
225-2V...1977-78..........8.4 to 1...........110.......................180