240z overheating at idle in traffic lights and intersections

[gundee]

That car should run and idle perfect with all that has been put into it. Even if it did run at 3/4 on the temp gauge. By the looks of those plugs it looks like 

the choke is stuck. Plugs are loading up. That is not from heat. Being in Panama I would disconnect the choke cables from the linkage and make sure the jet tubes are pushed all

the way up. (off) Then set the mixture per the video and go.

I would also back up and verify the cam timing was installed correctly since you changed cams.

I don't think all those ignition timing changes will do much unless that cam is correct.

What say you Z Therapy?

 

[Mark Maras]

 Excellent advice above. I'd also verify the float level and the needle height are correct. I've never understood why you had the nozzle adjustment so far down. (rich)  How does the engine respond to normal mixture adj. 2 1/2 - 3 turns down? Backfire out the carbs?

[jalexquijano]

Okay i can remove the air filter housing, air filter and set the ilde mixture knobs lowering them to 2.5 turns clockwise following the procedure found in the ztherapy video. I will download the FSM but believe me this will only cause backfire at the intake and loss of power. Ztherapy warned me of not opening the float valves and if i do i do not have the gasket replacement and will need to order some before attempting this. 3 turns down still backfires at intake.

Does a leak down test is the equivalent to a compression test? I try attempting the vacuum leak test connecting the hose to the brake booster but the needle in the vacuum tester does not even move! Maybe im attempting this in a wrong way.

Edited January 15, 2016 by jalexquijano

[psdenno]

1 hour ago, jalexquijano said:

 Ztherapy warned me of not opening the float valves and if i do i do not have the gasket replacement and will need to order some before attempting this. 

 

Not sure why you mention opening the "float valves'.  Do you mean float bowls?  There's not much that you can do with the valves actuated by the floats except to make sure they're clean and not stuck open or closed.  The gaskets on the float bowls can often be reused and are available through Nissan parts departments for a couple bucks if you do need them.

 

Have you considered using a Colortune device for synching the carbs? (http://www.amazon.com/Colortune-for-14mm-Spark-Plug/dp/B000E9VGNM).  The Colortune replaces a sparkplug and allows you to see into the combustion chamber while the engine is running to view the color of what's happening.  You can tune your carbs to an exact "flame" color and see if it's rich or lean by the color of combustion in the cylinder.  Do it once on the front bank and once on the rear and the carbs are synched. I've used one for 40 years and find it to be a good tool for fine tuning the carbs in conjunction with following the adjustment steps in the FSM and using a Uni-syn.

Dennis

[Zed Head]

Everyone is still giving advice that is complex and may be more than needed. 

He has an engine that runs fine, except for idle when it gets warm/hot.  He can either reduce the engine temperature at idle, or adjust the carbs for only idle performance.  Is it possible to adjust the carbs in a way that only affects idle?  He can't seem to get his mind around changing the hot coolant flow through the carburetors, or improving overall engine cooling by blocking the heater core hoses.  So, adjusting idle performance to handle the heat is all that's left.  Sync'ing the carbs may seem like a good idea, but why would un-syc'ed carbs cause poor idle on a warm engine?  It's an activity that doesn't seem to address the issue.

I can learn something myself here.  Is there a way to adjust the carbs so that only idle is affected?

Just trying to stay focused on the simplest solution before it blows up in to something really messy.  I thought that blocking two hoses was simple physically, but mentally, apparently, it's not.

[Jarvo2]

Has the subject of Needles been explored yet?

Stock Needles (N27/M58/etc) are known to idle rich and run lean at speed.  Rich = cooler, lean = hotter.  This is normally fine to be leaner & hotter at speed as the fan is pumping more air and air is flowing through the radiator.  Now with SM needles its the complete opposite.  Leaner at idle and richer at high RPM.  Could it be as simple as his fuel mapping through his SU needles?

[siteunseen]

2 hours ago, jalexquijano said:

I try attempting the vacuum leak test connecting the hose to the brake booster but the needle in the vacuum tester does not even move! Maybe im attempting this in a wrong way.

Are you connecting the vacuum gauge to the brake booster or to the balance tube's bung like the picture I posted?  It should pull some vacuum if you connect it to the balance tube behind the rear carb like the picture.

[siteunseen]

33 minutes ago, Jarvo2 said:

Has the subject of Needles been explored yet?

Stock Needles (N27/M58/etc) are known to idle rich and run lean at speed.  Rich = cooler, lean = hotter.  This is normally fine to be leaner & hotter at speed as the fan is pumping more air and air is flowing through the radiator.  Now with SM needles its the complete opposite.  Leaner at idle and richer at high RPM.  Could it be as simple as his fuel mapping through his SU needles?

He bought a refurbished set from Ztherapy, they should be SMs.

[siteunseen]

58 minutes ago, Zed Head said:

I can learn something myself here.  Is there a way to adjust the carbs so that only idle is affected?

 

When I adjust the air flow or balance the airflow I turn screws #10 in this diagram, it DOES effect the idle, but I honestly can't remember if tightening them raises or lowers the idle.  I would think tighter decreases airflow and lowers the idle, it's been awhile since I've gotten to play with mine since my motor has been on a stand for 6 months. 

[jalexquijano]

Well i guess i am not explaining my self clear enough. Lets see:

Crank the engine at the garage, if it does not crank immediately i need to pull the choke for at least 1 minute. After that i push it back. Temperature needle is at 0, drive the car from the parkway until i head myself to the streets. At the streets, i can drive around nice until i get to a couple of traffic jams, lights and after 15 mins of driving temperature reaches to a Little less than 3/4 in the temp gauge. Idle becomes rough lowering from 1000 RPM to 500 or to 400 sometimes and rises back. Eventually car stalls and i have to crank it again.

Its a real uncomfortable situation as i only remain with the possibility of driving the car on sundays when there are few cars and no traffic jams. I bought this car 2 years ago and have already replaced the following parts:

1. Pertronix ignitor 1761 and Pertronix Coil 40511 (3 ohms) bypassing the resistor.

2. Far 311 Race cam was replaced with Schneider 274F camshaft, with springs, lashpads and rocker arms. The car has a New Datsun L24 motor with crank and rods from a L26, special oversized 84mm flat top black coated pistons from D.L. Potter Engineering with E88 Head (This was done by Datsun LLC to the Previous Owner).

3. Water pump

4. Fully refurbished SU Carburetors by Ztherapy (US$650.00)

5. Fan clutch

6. 170 degree Farenheit Thermostat.

7. Airtex 8012S electric fuel pump (4psi)

8. New NGK Blue Spark Plug Cables.

9. NGK BP6ES Spark Plug.

10. MSA Fiberglass Fan Shroud

I guess the former owner new about this issue and decided to sell the car. With all the money i have spent including labour i could have bought 3 new engines. Unfortunately, mechanics here in Panama have few or scarce knowledge on this vehicle and hence i am looking forward to hire a US Datsun experienced mechanic that can assist me on setting up this car properly.

 

[siteunseen]

I love a Z but I drive a Camry everyday, maybe it's time you get a good daily driver and just drive the Z on Sundays.  You seem hellbent on driving your car in traffic jams knowing it's going to stall.  Persistence is a great attribute but sometimes you have to realize it's not going to work, no matter what you do.

 

[jalexquijano]

I have explained the problem in a very precise way and with all the facts. Hope someone comes with a solution that does not involve opening the float bowls or leaning the mixture more!