Carb problem where to start?

Electric choke, or mechanical (cable) choke? Or no choke at all?

If no choke, then you will have to continue to feather the throttle until the engine warms up.

With an electric or mechanical choke, a properly adjusted choke plate will have 1/8 inch gap when closed. A pump or two of the gas pedal to send a squirt of gas down the throat on a cold engine is all that should be needed to get it to start. Once it starts, the electric choke should begin to heat up its element/spring in the circular housing (has the + and - wire connection plugged in) to start pulling back on the choke butterfly. I'd say before a minute, the choke butterfly should be open all the way, and the fast idle is now off.

On a warm engine, the choke may close a bit (electric choke), but the same process occurs; choke spring/element heats up to open the choke butterfly.

Verify that the wire that plugs into the "+" side of the electric choke connects to a 12V source that is hot only when ignition key is in the on or run position. If it is connected to BATT or the vehicle battery "+", the choke will always be open, as it it getting 12 volts all the time, defeating it being a choke.

I am new to carb tuning at this level, but have learned this much about chokes. I won't show my ignorance here, but search this forum, there is a boat load of good info on this website.

For the vacuum advance... read the link below. This is absolutely the best info I have seen on this subject. Like @BillK mentioned, hook up the VA, you do need it and may very well fix all your problem. My BPE 383 had the VA locked out and the choke didn't work right when I got it, it idled very poor. I have since replaced the carb. My new carb (780 DP) has no choke, my VA is hooked up, and my engine idles good... Every engine is different, you just have to find what yours likes.


What is the "90 degree out" comment about?
Call Smeding, from what I have heard they have a great reputation and make an excellent product.

Side note, they do not offer a 650 cfm carb for the 406 if I remember right, probably a 750dp or maybe larger. 406 Eliminator is a 500+ hp engine full of really good stuff. Once you get it running right I am sure you will be very happy with it.

fairfax1000 said:

There's alot of overthinking here. Cold engine/no choke plate=throttle feathering till its warm.

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Not always, when a carb is tuned correctly it should run well even cold. Not arguing with u, cause most of the time we have just deal with and accept it. When a motor is only getting fuel from acc pumps it’s getting none from the idle circuit. Turning idle up won’t help. Everyone so far has been correct, timing, choke, it all matters. You can’t tune the motor if u can’t get out of the car cause you have to keep pressing the pedal.
In my case the idle mix screws turned off too much fuel. Increased timing helps , but with 12 degrees it should idle. Turn the idle up higher, it should get fuel and not need the acc pump.
It can get technical I had a lot of help from a guy way better with carbs than I am. The Transfer slot exposure needs be correct also. The rear transfer slot, I bet needs a bit more opening this will put the idle circuit in play. A choke up top certainly helps. By closing off the air it increases vacuum and pulls the fuel needed to run.
low floats won’t help. Higher fuel levels Inside the bowls help feed the motor.