Dies when choke is disengaged

[brantdedon]

Goodmorning, (for me, I'm in MS), I've been restoring this 85 C10 LWB. Rebuilt 305, rebuilt 700r4. A/C delete, no emissions anything, Holley Street Dominator intake, MSD SF HEI dizzy, Holley Street Avenger double pumper, custom gauge cluster. I just repinned the harness. But for some weird reason, my truck will sit there and run all day beautifully at 700 RPM. In gear it's sitting around 500 RPM. Idling perfect. but as soon as my manual choke is opened, it'll die instantly. Holding the throttle or not. I screwed in my idle mixture screws all the way and backed them out equally 1/4 turns with no change. I'm sure that I'm overlooking something. What do ya'll think?

[bd]

Check for a major vacuum leak and verify the float level.  Also, check whether the base idle screw is backed out too far and the engine is actually idling based on a misadjusted choke fast idle cam.

[brantdedon]

From what I can tell the float level is good. I pulled my sight plug, fuel didn't spill out. It was sitting right at the bottom of the plug hole. If I rocked the truck then it would come out.

[brantdedon]

And is the fast idle screw the one under the choke or the throttle linkage?

[blazer74]

With the choke closed u are richening the mix by taking away the air.
Open the choke goes lean with air and quits.

Could be idle circuit blockage.
You can remove the mix screws and use compressed air gently a couple of quick shots into the holes to clear debree and see if that helps,
WEAR GOGGLES!

Power valves blown normally go super rich at idle

Check your fuel filter just for the sake of it.

Other than that pull your front metering block off, clean the passages, replace the power valve and try again.

Assuming it's not an ignition problem.

[bd]

And is the fast idle screw the one under the choke or the throttle linkage?

Fast idle screw is on passenger side, curb idle screw is on driver side.

Did you spray for vacuum leaks?

[brantdedon]

I checked for vacuum leaks. I probably just need to rebuild and clean the carb. Shouldn't be that expensive or difficult. May not fix the problem but it's probably a good idea to nonetheless. Do any of ya'll have tips or pointers on rebuilding one? I know I can do it but I'll happily take advice.