Summer is coming in las vegas where the temperature will go up to 115. I have no over heating problem but I want to have the engine to run cooler because I have A/C all the time. I installed this winter an original fan shroud which is supposed to help running cooler in traffic at idle.

Is someone has other tips I can try to improve better idling in hot climate? Also, is someone has ever experienced isolating the gas lines to solve percolating problems? When it is very hot and after many stops and start again, the engine is harder to start and idle roughtly for some minutes. I suspect the gas is evaporating to fast in the carbs and and it idles better after when some cooler gas come in the carbs.

Finally, what is the thermostat degree recommended for hot climates

If I were living where you do, I'd do the following, or at least most of them....

1. Get the largest core radiator possible in your budget, 4 row would be best, but a 3 row is better than the stock 2 row.

2. Rebuild the fan clutch and make sure it's operating correctly. Look in our tech articles for a How To on that.

3. Use some Water Wetter from Redline in your coolant.

4. 180 degree thermostat, or, if possible, a 160 just for summer.

5. Flush the coolant on a regular basis and make sure the mixture is correct.

6. Make sure your timing is correct, if it's even 1 or 2 degree advanced it will contribute to overheating.

7. Block off the water line to the intake, or put a valve in the line so you can use it in the winter months.

8. Consider an electric pusher fan in front of the radiator, especially if you get into a lot of stop and go traffic.

9. Use the insulation on the fuel rail if none of the above helps the warm start condition.

10. You could add to the heat shield on the intake to more thoroughly cover the exhaust, and even add a heat resistant matte to the bottom of it(exhaust side).

What about a Thermo Fan ? you dont want the car to run too cool remember

My 240z being a concours original,I don't want to make any modification that can alter its condition. The improvements I have done is a four row radiator,a new fan clutch,timing has always been 0 degree and the newly installed original fan shroud.

I have a 180 thermostat. Is the difference would be noticeable with a 160?

Sounds like you have just about everything done.

A 160 thermostat should make a noticeable difference, but, remember, the temperature rating is when the thermostat is fully open, and not necessarily what temp your engine will run. In other words, with a 160 thermostat, your engine could possibly run at 180 all the time in traffic, while a 180 thermostat would possibly run at nearly 200 in the same circumstances.

I would definately try the 160 thermostat, and perhaps blocking the water to the intake before you do anything else. It may end the warm start problem and solve most of the issues you want to address. Or, just replace the water control valve (thermostat) at the back of the intake, as it could be that it is not cutting off the water supply at the correct temp and that is causing your semi-vapor lock.

Thanks to "to many z's" for the tips for running cooler.

I installed today a 160 thermostat and I see a big difference. Instead of the middle of the gauge, the needle stay now at the first third of the gauge in the traffic at idle.

Also I feel a notable change about the A/C. It is colder. I also put insulation on all A/C hoses that haven't had any.