Hello,
I have a 305 with M4ME quadrajet.
When i start the car cold, the choke runs good and it runs on high idle without any problem, but after 2 minutes, when i accel to disable the choke, the rpm drops to 700 and idle rough from 450 to 800 until the engine is hot. Also, it runs rough cold and almost stall on drive, but it runs good at part throttle and after 1300rpm even when cold. It takes about 7-8 min running before the problem stops.

Timing is at 6deg btdc with vacuum disconnected
stock engine
Compression ok
New cap rotor, wires, ngk ur4 spark plus
New coil and ignition module from summit (this kit below, seems to have a condenser delete on the kit)
https://m.summitracing.com/parts/SUM-850032
It still have the original centrifugal weights on distributor but the kit from summit came with a set of weights and 2 différent set of springs.

Spark plugs have black soot
I tried to adjust idle mixture as lean as possible, and tried with a rich mixture too, but it dont solve the problem
The engine runs OK when hot
Carb was rebuild

I think it worked better before i changed the cap, rotor, wires, spark plugs and ignition module, but im not ​​sure because i runned the engine only 2 times before changing this.

What the problem should be and what its the n'est things to check to begin?

 

Check the plug wires again - it is really easy to get #5 and #7 mixed up.
What type of choke does your carb have? Electric or coil heated by exhaust in intake manifold? If electric, is there 12v there? Does it heat up and pull off after 5-10 minutes? Is the vacuum choke pull-off working properly?
Did you use the white paste (dielectric grease) under the new ignition module?

 

Hello,
The wires are not mixed up.
M'y choke is electric, and all the choke operation is OK, i have 12v on it.
​​​​​​i used dielectric grease on the module.
I have changed the big vacuum hoses by prevention and started it after.
It runned full choke for the first 2 mins, then began to run rough at 500 rpm after i kicked the gas pedal to open the choke. At this moment, the choke was opened partially, and i revved the engine several times by kicking the gas pedal. At each kick, the choke opened a bit until it opened fully (after 3-4 min running at idle instead of running 8-10 min on the road.
Engine runned a lot better today. Maybe a vacuum hose had a bit slack and air entered from it, even if it seemed good visually.

Maybe we will know more in a couple of days...

How much time do you need to run the engine at fast idle in Summer? (At 90F exterior temps) is it normal it could take 4 minutes or 30 seconds is enough?

Do you think Hotter plugs could be a solution? I have NGK UR4 short plugs (gapped 0.40) because i have headers. Initially, i used ac delcos r45ts before m'y ignition kit change, but they were too long and the wires were burning on the headers. I remember the engine was running better cold at this time.

 

Stock engine - use the stock heat range.
Accel shorty header plugs are the shortest I have found.

Choke in summer - 30 sec for a cold engine.

Don't blow yourself up! You can test for vacuum leaks with an unlit propane torch (no mess). Engine smooths out of the propane gets sucked into a leak. Use AT YOUR OWN RISK!

I meant heat transfer grease, not dielectric.