yr
those late 302-308 and the EQ heads typically take less timing
The 440's I built with closed chamber heads and either FT or dished pistons took less timing than open chambers
413-426 with domed pistons and closed chamber (Max Wedge style) took a lot of timing- less with a "fire slot" they ran better with the domes "massaged" even with less Cr
I agree it's all about the newer combustion chamber shapes
an addendum to my previous open chamber post- open chamber can have less shrouding- can flow better at higher lifts- good turbulence at higher rpms
btw 361/413 truck takes less timing than passenger car- for those not familiar it has FE Ford style plug locations (or SBM)
