you could try it and see how it works, pressure was a year thing more than a particular engine, 7# caps were standard after 55, but with weak rads I've run with the cap loose for no pressure with both 235s and 283s without any problems
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics
