On 8/18/2024 at 8:38 AM, jalexquijano said:

Lets see if i can explain this better. Step by step:

1. Crank the engine with the choke pulled.

2. Let the choke on for 1 to 2 mins.

3. Drive for 20 mins

4. Suddenly get trapped in traffic jam and temperature needle raises to 3/4

5. Rpm needle starts to go up and down between 900 to 1000 rpm

6. Once traffic is clearing i accelerate and engine starts misfiring with hesitation simulating coughing.

This is the best written explanation i can give.

I do not understand needing a choke on for 1 or more minutes. In that climate where you live.

Use to start only if needed then shut off.

If that was my car I would have a radiator shop test and recore it if necessary. 

I had to do that on mine. But now you can buy aluminum radiator replacements for 240Z's.

It may be cheaper to buy one of those if the old one is bad.

You also may have one of those old style water pumps with impellers that rot away and cannot move water anymore.

You want the better type with cast impellers. 

Cooling systems should be in perfect shape in your climate.

7 minutes ago, gundee said:

I do not understand needing a choke on for 1 or more minutes. In that climate where you live.

Use to start only if needed then shut off.

If that was my car I would have a radiator shop test and recore it if necessary. 

I had to do that on mine. But now you can buy aluminum radiator replacements for 240Z's.

It may be cheaper to buy one of those if the old one is bad.

You also may have one of those old style water pumps with impellers that rot away and cannot move water anymore.

You want the better type with cast impellers. 

Cooling systems should be in perfect shape in your climate.

For the sake of order. I closed the jets and dialed them back to 3 turns clockwise each looking from above meaning the jet goes down. I have taken pics the fuel jet closed and opened to 3 turns each. Carbs balanced and rpm at 900. Should i go for a spin just as it is or should i put the air filter on?

Should i test the car again and then use the color tune to fine tune the fuel jets?

I would remove the ballast resistor and install a 3 -ohm coil, and then disconnect the choke cables completely and then use the color tune and rebalance the carbs !

I have used the pertronix ignition with 1.5 ohm coil and ballast resistor.

Worked just fine. No issue.

Test drive around the corner cylinder 6 5 and 4, 3.25 turns clockwise in each carb. No traffic jam test yet and without the air filter on.

On 8/17/2024 at 1:51 PM, siteunseen said:

Fuel fire and air 

You have the fuel checked off, it's good. You have the air filter housing off so no restrictions there. You should focus on the fire or electrical now that all 6 are black and sooty. It could be a loose wire since all of the sudden the spark plugs went black.

Did it not start running bad all at once? It should have after looking at the before plugs and the newest pictures.

Have a good weekend.

Site and Mark,

I set both jets at 3.25 turns clockwise and as a result only cyl 4 came out black and sooty after driving the car and temporary idling on red lights. Should i consider uaing a non fouler on cyl 4?

You could try one. It would not hurt anything.

I had one on a 2 cycle dirt bike that would foul the plug when I didn't keep the RPMs up high enough.

 

Thanks. In such a case if it does not foul the plug we could assume something is bad inside that cylinder? We know its not the seals as they were already replaced.

Lets not forget this is a California Datsun engine!  

That's probably the root of the problems!  After these years, I would have just purchased another engine with the stock cam and not messed up by a builder that doesn't know what they're doing.

Ok but we need to get to the root of the problem. Its cheaper opening the block and verifying instead of spending 3k in a new rebuilt engine plus shipping to Panama. 

It's cheaper to try a new ignition system!