Casting
#2531894 'X-Heads' {1968 thru 1971}....................................#3418915 {1970 340 T/A Heads}
Intake Valve............................... 2.02"..................................... 2.02"
Exhaust Valve............................. 1.60"..................................... 1.60"
Intake Bowl Size......................... 1.75" {87%}......................... 1.75" {87%}
Factory Combustion Chamber...... 67.0 CC's to 69.0 CC's........... 69.0 CC's to 73.0 CC's
Recommended Minimum.............. 63.5 CC's.............................. 63.5 CC's
Intake Port.................................. 1.16" x 2.27"........................ 1.16" x 2.27"
Exhaust Port................................ 1.25" x 1.75"........................ 1.25" x 1.75"
Intake Port CC............................. 160 CC's............................... 158 CC's
Exhaust Port CC........................... 70 CC's................................. 72 CC's
Intake CFM Flow @ .400" Lift....... 208 CFM............................... 206 CFM
Exhaust CFM Flow @ .400" Lift..... 135 CFM............................... 145 CFM
Intake to Exhaust %..................... 64.9%.................................. 70.4%
Intake CFM Flow @ .500" Lift....... 221 CFM............................... 220 CFM
Exhaust CFM Flow @ .500" Lift..... 142 CFM............................... 148 CFM
Intake to Exhaust %..................... 64.3%................................. 67.3%
The 'X-Head' is generally considered the best 'Stock' Cylinder Head, as the Combustion Chamber is a little tighter than the 1970 340 T/A Head
and 1971/1972 'J-Head'.
Both 'Ports' are near identical in volume. But the Intake Port on the 'J-Head' has a slightly better {miniscule} floor design.
The 1970 'J-Head' {340 T/A} have the Intake Push-Rod holes 'bored off-set', designed to allow for added Racer Modifications to open up the Intake Ports.
