Thread: Trouble idling when cold

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hey,
I have a 350 newly board engine with 9.5/1 comp. New Vortec Heads. Mild cam, about a 440 lift, performer manifold, and 725 road demon carb. The thing runs ok when it warms up, but i have been have weird problems with it when i cools off. When i start the engine in the mourning, it has trouble idling, it jumps around rpms alot and tries to die. Lately, i have had to sit in it to warm it up and keep pumping to gas when its about to die to keep it running. For the first 5 miles or so it runs really bad at low rpm, either with de-accelerating or idleing. It acts like a major vacumm leak. When de-accelerating i have to constantly pump the gas and power break it to keep it running. Im pretty sure i have to choke perectly tuned, and i sprayed ether to try to find a vacumm leak, but no luck. Now im leaning towards a intake manifold leak, or that i need to jet it up a little. It backfires sometimes, and always threw the carb, which means its running lean. My guess is that there is a vacumm leak, and its sucking more air then gas, but i don't understand why when i warms up it runs better. I can drive it until it gets completely up to temp, then park it for 30 minutes, jump back in it while it should still be warm, and it acts up a little until i drive it again. Im know im gonna have to tear into it and find the problem, but does anyone have and suggestions or relations to this problem?
Thanks, Bob B.

Most likely problem is the vortec heads...
Those do not have the exhaust ports in em that feed the bottom of the intake.
without a little heat to vaporize the fuel on the bottom of the intake. she's gonna stumble till the engine builds nuff heat to do it. For a good cold run with a carb ya gotta have those heat passages, on an elect. injected car ya dont as the puter can adjust for it.

I agree that the Vortec heads not having the heat passages doesn't help the problem, but before i had the demon carb on it, i had a edelbrock carb and manifold and i didn't have this problem. ]: