What could be wrong?

I'm having trouble starting when cold. When the engine is runing (at parking) sounds great with or without the choke.

The trouble begin immediately when I drove without the choke. I get "explosions", gas spills in the air filter housing.

But when I drive with open choke the explosions disappear .

I'm running an automatic 240z with L28 & roundtops.

Mario,

I would start with a basic tune-up. New NGK spark plugs, cap, rotor, points and set the timing. If you haven't done so already adjust the valves. Next would be to adjust the carbs. If you haven't done this before then I would suggest getting the "How to" video from Z-therapy. Ojala esto te ayuda, porque sin poder ver ni oir yo no te puedo ayudar.

I would first check my float levels and make sure they are accurate..

You might want to clean them up too. Mostly if you are haveing spillage it is due to incorret float levels and or the needle staying open.

A rebuild of them may be in yoru future.