Tranny kickdown cable

Does anybody know how much tension should be on the kickdown cable when it's hooked up? I have a 76 Nova with a 73 307 in it. My car came stock with a straight 6, so things don't line up exaclty the way they used to.
There seems to be a lot of slack in it. When I first hooked it up it was super tight and I couldn't even open the throttle all the way up. I bought an aftermarket combination throttle and kickdown cable bracket. Now when I'm driving and I gun it it doesn't seem to kick down and take off like it should. It's fine if I manually put it in 2nd gear though.
Any help would be appreciated. Thanks

Open the throtle up all the way(with the car off) with the throttle all the way open the kickdown cable should be tight