Jets are gettin big!

Idle it runs 160 all day rite on the number... When i cruz it climbs up to 180-200, ive seen it as high as 220... I jus turned up the timing to 18idle/39max and took it for a lil spin and it ran 170...so i think im on the rite track with timing, but how far is too far for max timing?? Or is their no set number, jus back it out when it starts pinging??.... Im runnin kb-107 pistons with stock 360 (1.88/1.60) heads,67cc chambers (i think) machine shop said compression is rite around 10:1...air gap intake with holly 4150 750