Hello Members   Have a 292 that was put together in early 1960s.  Has .060 over Jahns ( 5/8" dome cast pistons ?) as I recall raised comp. ratio 2 points. Car was a 55 with a 6 volt system that would not spin fast enough to start, had to change to 12 volt with 6 volt starter. Retired it and then octane rating dropped. Also recall that I had  to use 103 octane fuel available at Standard stations. Had non posted G heads as i remember only once blew head gasket. My question, anyone here have any info about Jahns pistons different comp. ratio?   If pistons do actually  raise comp 2 points   to 11.7   would using 471 heads/ thick gaskets get it back down.  Really not interested putting much $ in it ( finding 3.81 or 3.82 pistons) ?  Thanks Cos