I have a 2.8L V6 1985 camaro. I just finished putting in a new cam, starter, oil pump and pan, timing chain, and converted to a serpentine belt system. Now when I am trying to start the car it will just die instantly unless I try I press the pedal down then it will start but I have to keep putting my foot on the gas pedal to keep it running. The rpm is really high, too. As soon as I stop giving it gas it dies it will not idle. I am thinking I have a vacuum leak on the manifold. The distributor has not been timed and locked down yet but even then I should be able to get it to run even if it does terribly so I can set the timing. I know the valves are adjusted right and the distributor has the correct firing order and it is not 180 off. Also the header does not have its gasket where it bolts to the Y shaped exhaust which makes it loud buy I dont think that would case the problems I am seeing. Any ideas why it is not idling under is own power? Maybe I need to just floor it alot to get the engine running and it will figure out the rest itself?

 

Very rarely does " floor it alot to get the engine running and it will figure out the rest itself?" Help do anything more then brake parts....so no....
I suspect your on the right track with a vacuum leak.
Get out the Carb cleaner or brake clean and spray around the intake until you find it.
Good luck.