340 timing need some advice on rufff timing

i have a mild built 340 10 1/2 motor stock carb elc ing med purp cam
x heads stock intake not a crazy motor just nice mild car

book says 5 degrees i set it to that ran like crap i went to 10 seems better but this car is a straight dog i think my wife's cavalier is faster lol
ive done all i can think of.

set vacuum at carb adjusted the air fuel messed with the timing i ask what should i set it at because the book may be way off of what these motors like and some one may chime into say 15 or 20 will get me closer.

i caped the advance didn't see any real difference then one time the car came alive ran super hard then pulled in drive way and the idel was way off running at like 300 rpm what the hell was that all about cracked it open and then it was fine cars got me pulling my hair our

also no spark knock at 10 degrees ether

i know there are a ton a variables but im just fishing for fresh ideals

no vacuum leaks ether almost every thing is brand new minus the dizzy and box carb was just redone

im running ngk plugs also dont think it will matter but maybe