Asides from that the engine still pops while decelerating at second and 3rd gear. I have no vacuumn leaks. Pop pop pop pop.....

 Prior to changing the radiator in my 71 240 I had similar problems in stalled and stop and go traffic. I found the best solution at that time was to turn the engine off until traffic moves again. The Z would restart with a click of the key so it was little inconvenience. Also, when in slow traffic, keep the rpms as low as possible. Every time a spark plug fires it produces more heat.

Guys - a well maintained engine shouldn't be doing this...in any weather ! Nissan did not make it so.

What does your TEMP gauge show. My needle stays on the right "leg" of the M and my other 240 was the same exact way. If I'm not mistaken Nissan has a 165F thermostat and a 180F. Are you using a thermostat, is it a Nissan because the cheap ones are no good.

Do think the motor is actually hot or are you thinking it's the fuel in the carbs percolating?

The "pop pop pop" means it's not tuned properly. It could in the timing or ignition or the carbs, any number of things.

The last I remember you had found an L motor experienced mechanic. What happened with that? 

I think an infared temp gun would be money well spent. They're pretty cheap now. Point the red dot and see where it's hot.

https://www.amazon.com/Infrared-Thermometers/b?ie=UTF8&node=9931459011

Good luck with your problem.

PS Back the timing up and remove the air filter, then see what it does.

PSS Read this thread if you have time.

 

 

Edited December 11, 20213 yr by siteunseen

I got rid of the pop pop pop today by tuning the carbs to 4 turns clockwise both and rpm set to 1000. Now i need to knock down the heat that makes my car stumble snd misfire after 5 to 10 mins stuck in traffic. Any recommendations other than removing the fan clutch and installing dual electric fans?

I think electric fans may be a good idea considering where you live. 

Some mechanic over here told me i should consider investing in ceramic coated header? Will this help?

@siteunseen Cliff has a Z with ceramic coated headers. As I recall, he says it does help.

4 hours ago, jalexquijano said:

Some mechanic over here told me i should consider investing in ceramic coated header? Will this help?

Mine runs "warm" even in the heat of our summer here, high 90s farenheit.

My carbs domes are cool to the touch after driving. Good flowing fuel and the ceramic header I guess. Also no coolant flowing through them.

Try a digital thermometer in the radiator while it's parked, no air flow other than the fan. That is like traffic jams I would think. Mine runs at 175 farenheit with the thermostat open and coolant flowing.

 

 

Well i do remember  shutting the water flow passage that runs on the back of both carbs by removing the intake manifold valve to reduce any kind of heat. My car also has the antibackfire / smog emmission system removed. Any recommendations on how to tackle this misfire caused by overheat when coming out from traffic jams?

The last photo looks like your heater core is bypassed? I’ve read about bypassing it and that it’s better to plug the fitting at the back of the block rather than looping it. I guess this is how the factory heater core works (stopping flow, not rerouting). Perhaps this could help? 

Yes the heater core was removed. Too hot in Panama. Asides the Gen 2 Mini ac system neede space inside the dashboard.

What do you recommend?