So I finally got my 454 swapped into my 91 RS and am trying to get her running. I had a Holley on it but I couldn't get it running good. So I switched back to a good old edelbrock. But this is working either!! When I crank over the car it spins and spins when I let off the key it fires up, after I stop cranking the. It fires!! I am so lost. Also when it lights off it runs up real high, 3000 rpm, then it dies again. Any help is greatly appreciated. Thanks!!

How do you have your ignition power hooked up? That sounds like CLASSIC startup symptoms when you have power to the ignition in the RUN position on the key but no power in the START position (you need power in both). It's all jazzed up and ready to fire while cranking but there's no spark. In that instant when you let the key back to RUN the ignition turns on and just catches fire as the motor is spinning down. TA DA! It runs. But it makes you want to pull your freaking hair out catching that knife edge between START and RUN.

That's my best 1000 mile away internet guess.

That's similar to what some people told me. But i don't see how that can be. When I put the holley carb back on it idles fine, doesn't run but it idles. Then with the edelbrock it craps out. I'm at a loss

Sounds like a wiring issue to me.

I just don't see how it could be wiring though. Because it works fine with one carb then terrible with the other. I've swapped them back and forth a couple times and it always fails with the Edelbrock

If it were me, I would put which ever carb on it that idles okay at first just so I could set initial timing FIRST.

Yep. I set initial timing at about 16*. Is that enough for a BBC