what do you mean by 8* of timing? is your initial set to 8*? stock is roughly 10*, most guys will advance to around 16*.. rule of thumb for juice is to pull 2* per 50 hp shot. i guess what im saying is, i would find what my car likes on motor (16* for arguments sake) and pull 4* from there (12*). if all this is the case, you may be shorting yourself about 4* of advance.
replaced the 93'ish coupe with a 76 F100, 393, 11.5:1, TEA CNC 205 TW's, custom Hyd Roller, Super Vic, 830 HP, AOD, Edge custom conv., Silverfox SPT-MAC-TB.