This may give you some idea .I've done "lot" of sixpack carb restoration,almost all big block that still had plugs were 2 turns or "very" close.I don't think I ever had a small block set that still had the plugs that hadn't been messed with so I really can't answer your question,Scott Smith possibly could. I will tell you if you remove the plugs to adjust,be very careful,those screws are brass,been there almost 50 yrs,the cork seal gets like concrete and you can take half the head off quicker than you can blink.If you can't get the broken screw out,this is the only alternative.