Will there be reheating problems if installing an AC System to a modified 240z?

[jalexquijano]

My 240z has the following upgrades:

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 and Far 311 New Race Cam with 2 original SU Hitachi round top carburetors which have been rebuilt.

I want to install a GEN II mini evaporator and a Sanden 508 compressor to my car:

http://www.summitracing.com/int/parts/vta-66005-vuz-a/overview/

However, before attempting this i have been advised by a Mechanical engineer who is now overlooking the car i must first swap to a Street cam preferable the original stock cam and components or else i will have overheating problems when i turn on the ac while in traffic or stops situations. I am also not fund of the irregular idle and would like the car to keep 900 to 1000 RPM at idle.

We are still looking for the specifications of this FAR 311 Race cam and have not found them. Is it really necessary to change the cam to avoid overheating and stalling problems at idle?

Any opinions on this issue.

[Kurbycar32]

My stock 260z overheated just by having a completely disconnected condenser mounted in front of the radiator. more than the internal parts of your motor i would be concerned with air flow over the radiator. You will need to increase that flow by use of a shroud, bigger fan, electric fans etc. Those are facts. My opinion is that this might be easiest by upgrading your radiator and using electric fans, though other members might disagree with the use of electric fans due to the weak electrical system in these cars.

Your mechanical engineer friend is overthinking things. Adding an AC to a car requires attention to the cooling system and also a provision for increasing the idle when the AC is engaged. Look at the differences between older cars with and without AC and you will find the major differences match what i just detailed.

[madkaw]

You have to have a car that idles well to have AC. Doesn't sound like your engine as is will support an AC system.

[zKars]

I have the vintage air Gen II system in my modified Z motor with a lumpy idle. It idles just fine when the compressor is on. The load with the compressor on is not significant.

If you put too much Rxxx refrigerant in the system, and the pressures are too high, and the compressor makes noise and overloads, THEN maybe you will problems with idle. but if its filled properly (ask me how I know....) then it works like a modern car. At worst you might have to is turn up the idle speed a bit.

Remember that a fan on the AC condensor rad is critical if you are going to spend a lot of time idling in traffic. Don't rely on the engine fan to help with that.

[jalexquijano]

My car has a 3 row racing radiator not the stock radiator as you can see in the picture. Can you make a short list of the additional parts i will need to purchase so i wont have to mess with the FAR 311 race cam? Which electric fan is recomendable and do i need to purchase also a fan shroud? I live in Panama City, Central America and there is a lot of traffic here where the temperature can rise to 34 degrees Celsius.

My stock 260z overheated just by having a completely disconnected condenser mounted in front of the radiator. more than the internal parts of your motor i would be concerned with air flow over the radiator. You will need to increase that flow by use of a shroud, bigger fan, electric fans etc. Those are facts. My opinion is that this might be easiest by upgrading your radiator and using electric fans, though other members might disagree with the use of electric fans due to the weak electrical system in these cars.

Your mechanical engineer friend is overthinking things. Adding an AC to a car requires attention to the cooling system and also a provision for increasing the idle when the AC is engaged. Look at the differences between older cars with and without AC and you will find the major differences match what i just detailed.

Edited July 31, 2014 by jalexquijano

[Kurbycar32]

With the aftermarket radiator its doubtful that you will get an OEM shroud from a Z to work. You can try different shrouds from other vehicles but that could be an endless journey. you could make a shroud out of aluminium with little more than a jigsaw and a drill, and it might even look nice if you're careful. This radiator/shroud combo set details what your looking for when you build your own. Notice how the shroud surrounds the fan and radiator:

Fans blow air much better than they suck it, and your engine fan is sucking which is why the shroud helps. This is where you need to play it by ear and see what works for you. Start by replicating a typical OEM setup: Mount the condenser right to the front of the radiator and see if both it and your radiator operate at good temperatures, you might get lucky. If you cant keep things cool you can start getting creative:

You might consider spacers when you mount the condenser in front of the radiator. Putting a gap will allow air to come through the gap instead of forcing all air flow through the condenser and the radiator. The trade-off here is better radiator air flow and less condenser flow. You could also wire an electric fan just for the condenser that only engages when you activate the AC. Lots (maybe all?) of modern vehicles with electric fans actually do force the fans on when the AC is engaged regardless of engine temp to cool the condenser.

You car should idle without fail all the time even in horrible conditions. If you car doesnt you should start there. The easy way to do things is to increase your idle from say 750 rpm up to about 900 rpm during the summer, or whatever you car idles at nicely with the AC engaged. If you want to get fancy you can build in an idle air control valve to automatically adjust your idle when the AC is engaged. Thats sort of a separate topic and you shouldn't attempt it until you have a functioning AC system

[Stanley]

Can't see the brackets on the side of the radiator, but otherwise it looks like mine, which is the Champion 3-row from MSA. I'm using the fiberglass or CF shroud from MSA, works fine. Might have drilled a couple mounting holes in the shroud but that's no big deal.

A couple weeks ago you posted a link to the Schneider 311F cam. Did you find out that wasn't it? If that's it, or it's about the same grind, it's for racing, so you might need to set the idle to at least 1500 rpm to make it more drivable.

[jalexquijano]

1,500 RPM thats too high!!! Since i have a Champion 3-row radiator, what electrical fan and shroud should i purchase before installing the AC?? Please advise. Which vendor?