A little background:
I have a 390 out of a 74 f100. It has been transplanted into a 79 f150 4x4 by the previous owner. The truck had set up for about 2 years when I bought it. It has an Edelbrock 600cfm carb that was in bad shape (gunked up). Bad enough it wouldn't run. I tore the carb apart and cleaned it and got a rebuild kit for it (including floats). I followed the directions that were included in the kit, as this was my first Edelbrock rebuild. I have a gas tank from a boat (6 gals) that I'm using to run off of cause I dont know what shape the gas tank in the truck is in. I did a tune up (plugs, wires, cap, rotor, oil change). I checked the fuel pump pressure and it is 6.5psi. Previous owner says it has a different cam in it, but didn't remember the specifics.

The problem:
It wont idle unless the choke is on. (previous owner didn't even have a choke cable, so this is a new problem, I assume) Then it idles around 1100rpms. If you idle it down (via the idle adjustment screw on the throttle) to about 800rpms it sounds like its going to die and then revs up to ~1300 and idle back down to 800 and then back up to ~1300, again and again. I tried using a vac gauge to help me out, but it wont hold a steady reading with the motor bouncing up and down like that. After you get the idle mix screws out about 3.5 turns, it acts like they quit doing anything.

Any ideas on what I need to do to get it to run smooth?

Thanks

james

 

I'd wager you have a vacuum leak somewhere.

 

i have sprayed carb cleaner all over the intake and vacuum hoses trying to find one. My brother is coming over today, so maybe with a second set of eyes and ears we can find it, if its there.

 

That's a textbook case of a vacuum leak. You'll find it.