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jalexquijano

5 to 7 mins to warm up when cold with choke pulled

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Last night while fine tuning my round top 3 screws mixture adjusting nuts to mantain a correct idle while preventing the spark plugs getting carbón fouled due to rich mixture, i discovered that my car is taking 5 to 7 minutes to warm up and i need to drive it with the choke pulled until the temperature at the temp gauge reaches to 1/2. Otherwise, if i remove the choke, the acceleration is very poor and tends to fail. As part of the history of this car, i did remove the inline  heat control thermostat and plugged the coolant lines on the back of both carburetors to lower the percolation. In view of this, i have the following questions:

1. I live on a Tropical warm weather so i will never need the heater. If i install the inline heat control thermostat shown in the picture back, my car will warm up faster and the choke will only need to be pulled 2 to 3 mins?

2. Gas Mixture nuts were adjusted from 2.5 base and fine adjusted to 2.65 turns clockwise. Idle at 1000 RPM and balanced. Lowering it more than 2.5 turns clockwise will cause a loss in power at the moment of driving. Is the mínimum aceptable revving shown when you accelerate and it does it smoothly? Once this is accomplished, then the mixture is the correct one?   

Thermostat rear carb.jpg

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Old school method of checking the mixture is the color of the spark plugs. Simple and relatively accurate.

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I also agree check the plugs ! my carbs are set about 2 turns out ,I can change the color of the plug with 1 good drive black to tan and than to white each time . my plugs are set to very light tan at the tips and she runs great. every time you adjust the mixture recheck the balance on the carbs .I also use a non resister plug like the ngk  bp6es-11 and the car like it better. I have the inline heater control thermostat and it works great. my first drive when cold I use very little choke for a couple minutes than its fine after that. if I drive the car several time that day no choke is needed at all.

Edited by kully 560

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My 240z, all stock with round tops has around 2.6 turns for the fuel as well.  I used to have it close to 2 and once I got them to 2.6 it seem to wake up.  I still start with the choke on, slide it to half choke after a few seconds of running as the RPMs climb, and then after 2-3 minutes of idling or driving I slide it off.  All cars and carbs are little different.  Add the humidity that day, temp, etc. and you just have to keep working until to find the right spot for everything.

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Thanks to all of you. SInce im fighting with fuel percolation issues at the carb i am still thinking if reversing and installing the inline heat control manifold thermostat back will get the car warmer more fast or if this is irrelevant. Anyone has a picture of the correct color the spark plugs should come out if the AF mixture is correct?

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