ok im working on a friends 70 cuda 440 with six pac ... ALL NEW CARBS

I have no Vac leaks i can find.. It will only run/idle if i have the crub idle turned open to 1/3 throttle ... and then it runs for a bit and stalls out ..if i turn the mix screw ( ether way )it will die off ...

now it does run backwards when you cut off the key ... but the timming is in the sweet spot and there is no Vac advance hooked up on the car ..

I was thinking power valve it toast ? to start