Won't Shift
 

I just installed a new motor and transmission into my 1968 El Camino everything is brand new. I have 2 question.

1. It won't shift during hard excelleration, it's fine in normal driving mode.

2. It seems to slip in low gear, could I have overfilled the transmission with fluid?

Any help would be great.

1. What trans are you running?

2. Does it shift if you let of of the gas after a hard accel?

Won't shift
 

The trans is a 350 and yes it shifts ok if I let up on the gas. I have tried using both the Large and small Vac tubes in the front of a new Edelbrock carb?

Check the kickdown cable adjustment, generally if it is a modulator problem they won't upshift.