I just got my q jet back from someone who rebuilt it for me. Apparently it is an M4MC with an electric choke. Before he rebuilt it, the carb would literally spit gas out from flooding most likely. That problem has since been fixed, but as soon as the key is turned, the carburetor just climbs in rpm. It also spits out smoke consistently from my open headers and is sickeningly rich. Before the carburetor needed rebuilt, it was running fine and the 305 is perfectly fine. I shifted it into drive and I was doing a burnout without even touching the throttle

I know next to nothing about carburetors really, but I checked the throttle cable. It isn't stuck or anything. We adjusted the idle screw by the throttle but there was no difference. The choke plate seems to be really wide open even when the engine is off. Also since it's a "fresh rebuild," I've heard the air/fuel mixture needs to be adjusted and possible the fast idle? Or it could possibly be a huge vacuum leak, but since it's so rich I wouldn't think that's it, idk.

Also, the engine can't be left on long enough for it to even warm up. We keep the choke plate down with our fingers so it revs lower "1500-2000" and even then it starts to die out. No backfires though, just smoking, really rich, and extreme idle.

Any ideas? I'm at a loss. Thanks in advance guys.

 

Lots of ideas. Too many to list. Pop off the throttle cable (temporarily) so you rule that out as a reason for the throttle to not return to curb idle. Check to make sure the secondary throttle plates are fully seated in their bores. Vacuum leaks should be checked for, obviously- something big like the PCV or power brake booster line. Fast idle cam not backing off even if the choke is open (who knows why- could be the linkage wasn't assembled properly during the rebuild). It could be damned near anything, but remember that SOMEWHERE a lot of extra air is making it into the motor. That'll either be past the throttle plates or somewhere else. You just need to figure out where.