On 30/3/2018 at 7:41 PM, Mark Maras said:

@jalexquijano Looking good. Let's assume that the mixture screws are close for now. Am I correct that the gremlin we're working on is the sputtering before it's warmed up? Next time you're out and the engine is warming up and sputtering, note the temp on your gauge and push the choke knob slowly forward. I'm trying to figure out if the sputtering WHEN COLD is caused by a rich or lean condition. If the sputtering improves when you pull the choke it means the the mixture is lean. If you push the choke forward and the sputtering improves the mixture is too rich. Please note, I'm not talking about adjusting the mixture screws at this point. I'm trying to get a feeling as to what the engine wants when it's cold. This problem could be just choke related. Not being in Panama and being able to drive your Z, I'm guessing that the sputtering is caused by too much choke. Too little choke on a cold engine will cause it to fall on it's face when a load is added. I'm betting that the sputtering will improve with a little less choke. Try it. Remember tho, it's not good for your engine to be pushing it HARD when it's not fully warmed up.

Ill try this test today! Is it better if i try it with the air filter on? How much  minutes should i drive with the choke knob pulled? Until the temp gauge reaches half?

Edited April 1, 20187 yr by jalexquijano

Here is my experience with a stock 240 with 12 yr old Ztherapy carbs.
On cold start up (after a sitting for a couple days) I pull my choke all of the way on while starting. Once it fires I reduce the amount of choke enough to let it idle at about 1200 rpm or so. As the car beginnings to warm the rpm’s tend to increase allowing me to reduce the amount of choke. Eventually I am able to completely shut off the choke and it idle in the 800-1000 range showing on the tach.

Ps; running on a mechanical fuel pump.

Good luck


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17 minutes ago, 7tooZ said:

Here is my experience with a stock 240 with 12 yr old Ztherapy carbs.
On cold start up (after a sitting for a couple days) I pull my choke all of the way on while starting. Once it fires I reduce the amount of choke enough to let it idle at about 1200 rpm or so. As the car beginnings to warm the rpm’s tend to increase allowing me to reduce the amount of choke. Eventually I am able to completely shut off the choke and it idle in the 800-1000 range showing on the tach.

Ps; running on a mechanical fuel pump.

Good luck


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 @7tooZWell said.

@jalexquijano You can get a "feel" for the choke location during warm-up (while driving) by gradually easing the choke off while you're GRADUALLY accelerating. As you slowly push the choke knob forward, you'll feel the engine lose power, at that point give it a little more choke and you'll feel the power increase. Too much choke when the engine is warm will make the engine run a little rough with a decrease in power and could increase the possibility of backfire from the exhaust due to the rich fuel-air mixture.

 Yes, do all street tests with the air filter installed.

Edited April 1, 20187 yr by Mark Maras

1 hour ago, jalexquijano said:

The temp goes to 3/4 on the temp gauge on traffic.

On my '72 the normal day in and day out gauge reading is the needle on the right leg of the M. When I look at my gauge it has TEMP written on it. The needle lines up with the right side of the M in TEMP. Right before the P.

That is between 170 & 175 degrees measured many times with a meat thermometer inside the radiator while flowing coolant, thermostat open.

I have a 180 Nissan thermostat. It opens at 180 degrees. After the thermostat opens it doesn't matter if it's a 160 or 180. It's open and won't close. In your climate I can't see any reason for a 160. Those open sooner for the heater core or heat inside the cabin.

I also have a spare original nissan oem 170 degrees lying around in the deposit.

If and when you put one in make sure the little jiggly hole is on the driver's side. Our motors tilt to the other side and that hole lets air pockets escape. 

3 hours ago, Mark Maras said:

 @7tooZWell said.

@jalexquijano You can get a "feel" for the choke location during warm-up (while driving) by gradually easing the choke off while you're GRADUALLY accelerating. As you slowly push the choke knob forward, you'll feel the engine lose power, at that point give it a little more choke and you'll feel the power increase. Too much choke when the engine is warm will make the engine run a little rough with a decrease in power and could increase the possibility of backfire from the exhaust due to the rich fuel-air mixture.

 Yes, do all street tests with the air filter installed.

3.5 to 3.7 turns clockwise. Choke on for 10 to 12 mins until it reaches half the temp gauge. No coughing then.

@jalexquijano "choke on for 10 to 12 mins", did you leave it pulled all the way on until the engine was warmed up (presumably temp at half) or did you gradually push the choke forward as the engine warmed?

All the way and then push it back until it stopped coughing.

Excellent. The coughing you're describing is a too rich mixture caused by too much choke. You've figured out that the choke can and should be adjusted to suit the conditions, ambient and engine temperatures. While I'm thinking about it, should you ever want to see if the fuel mixture is too lean (when the engine is warmed up) gradually pull the choke while you're SLOWLY accelerating. If you feel the power increase the mixture needs to be a bit richer. Drive it for a few days or until a new question arises. Oh yeah, have you driven by your old mechanic's shop yet?

I can start pulling my choke off as soon as the needle starts to move.  I'm pretty sure it's for cranking and not meant to be left on until full operating temperature.  But what do I know, I'm just here for the funny conversation. 

2 hours ago, siteunseen said:

I can start pulling my choke off as soon as the needle starts to move.  I'm pretty sure it's for cranking and not meant to be left on until full operating temperature.  But what do I know, I'm just here for the funny conversation. 

I'm sure you meant PUSHING the choke off.