Pinch the rubber fuel inlet (and return, if equipped) overnight and see how it starts. In one of the shops I ran, the Italian cars carbs would drain back to the fuel tank, overnight. this happened on warm days, as the fuel in the gas tank contracted w/ temp drop, it would pull fuel, if the check valve in the f pump was bad.

 

I put the carb back on today, and now the tach and temp gauges are acting weird.

The tach reads accurate while driving, but as soon as the key is turned off, the tach slowly crawls to 1000 rpm and then just sits there. If I turn the key back on as the carb MCS clicks, the tach drops back down to 0.

Also, now the engine temp gauge reads the middle of the temp range around 210, even when the car is off.

I assume I bumped some bundle of wires or something when reinstalling the carb? These issues weren’t present previously.

 

Did the carb rebuilder give any warranty?

 

Completely normal. It is totally free to go wherever it wants to when the power is off.

Temp gauge however, DOES have a spring in it, that should return it to 0 (fully cold) without power. OTOH nothing you can do under the hood will change that. It will also stay at 0 if the sending unit wire is disconnected, and go to max if it's shorted to ground. It's a green wire, sending unit is in the driver's side head, between the #1 & #3 spark plugs.

 

Get a new distributor. You already had the plugs and wires done.
Your entire secondary ignition system will be new.
If you still have the issue, then you know it's carb related.

 

it's common for the temp gauge to fail like that. a replacement may be still available on rock auto.