Seasons greetings to all.

I have a 1972 240z. Upgrades include, all OME, Ztherapy carbs, distrbutor,fuel pump, fuel filter,gas tank hoses, plug wires, timing set,cap and rotor. When the car sits for more than 5 or 6 hours, I have to crank it over for quite a while before it starts. PS new spark plugs.

Any ideas. Thanks in advance. Bill.

Does using the choke 5 or 6 hours later help? Perhaps the choke isn't properly adjusted. With the choke lever pulled all the way back, the fuel nozzles should be pulled down out of the carb body about 1/4" and the throttle valves should be cracked open. Be sure to adjust the valves if you didn't do that yet...

Are the float levels set right? I just bump my starter and it starts instantly. Sounds like the fuel level could be raised.

As kenz240 mentioned a functional choke is needed. In cool weather mine needs a bit of choke or it behaves exactly as you describe.

Is the timing set right??

Just thought I'd mention the obvious. Don't know how long you've had your Z.

I'd check the choke lines to be sure one of them hasn't slipped out of the holder and is holding the choke in on one of the carbs. Also, check the linkage between the carbs... the springs especially.

Just thinking here.