Black Fuel Smoke Backfire Busted New Muffler

I went through 30 pages and didn't see anything related to this question. If it's been answered prior it's time to readdress the question.

'87, carbed, 2WD, 5spd, truck.

When cranked from cold much black fuel smoke is present. Pulled the air cleaner top and primary choke plate is open. Secondary isn't. When secondary is opened smoke stops and idle smooths out when plugs clear.

If I recall (it's been many, many years) the heat mass on the primary is operated by electric current. What operates the secondary? It IS supposed to be open when warmed up....Right?

A new exhaust was installed W/O cat.con. Unburned exhaust was so bad it must have ignited and blew the muffler seam out.

Any help would be appreciated.

Is it possible your carb is leaking gas out of the bowl and dumping it into the intake when it is sitting? I don't think the secondarys open unless the throttle is significantly opened. I don't know if the secondarys are vacuum or mechanical.

The float level may be too high also.

The choke is electric, everything else is mechanical.