I have a 64 impala with a turbo350 tranny off a 79 caprise, I recently switched the 283 out and put a 350 motor. WELL when I was putting on the intake manifold is when the (big bang) happened and relized it was a vortec 350 motor. I dont know what it came off of. I have a hei distrib off a 75 chevy. 600 edlecbrock carb and a electric pump of 9 pounds I had two people time it. It turns on and sounds great like it can peel off the road. BUT.......BUT........when I put it in drive, it goes like ten miles an hour and sould like a dam lawnmower. Im to the point if throwing out the vortec cutinng my loss and rebuliding the 283. so what u guys think.

 

Does it have a Vortec intake manifold?

If not, spend the couple hundred (max) to get a Vortec-specific intake manifold on it. That'll cost a lot less and have a bunch more potential than rebuilding a 283.

If it does have a Vortec-specific intake on it, then it's probably something simple with the ignition.