Technical New AC…and now SBC runs 30 degrees hotter

Just FINALLY got the new AC installed. The weather just got WAY hotter and is in the mid 90s. Prior to install , the engine would hold 180 degrees, plus or minus a needle width. Now she’s running around 210 with the AC on. I haven’t had a chance to joy ride it with the AC off yet, but I assume it’ll still hold 180, because the condenser has actually been in place for a while, just not plumbed in.
I wIll drive it a while with the AC off to verify engine temp. Did I mention it’s HOT outside?
- I’m running a 180 thermostat.
-The condenser has about 1/2” clearance in front of the rad.
- My rad sits in front of the rad support, so an additional fan is not an option.
- I do not have a fan shroud.

Current plan is to space the condenser about 1-1/2” from the rad, which requires mod’ing my hood latch. After poking around under the hood of a 93, 95, and 01 truck, it looks like the factory gap is ~ 1-3/4”.
I’ll also fab up an aluminum shroud.
Any other amazing tips, advice, or wisdom tidbits before I manage to hose this up?

 

A proper shroud will help exponentially

 

Shrouded electric fan will cure your ills.

 

210 is normal for today's cars. The condenser is now putting out heat.

 

My 2 cents. I would do the shroud first and see what improvement that makes before doing the hard stuff. That very well might solve your issue. Good luck.

 

Like Johnny said,,,,that condenser is putting a lot of hot air directly into your radiator fins .
It can’t help but run hotter,,,,,, but 210 is not unreasonable,,,,,for todays weather around here .
Spacing the condenser further from the radiator won’t help that much either ,,,,,,but a shroud and an electric will assist .
It’s just gonna be hotter with that added heated airflow.

Tommy

 

I would go to a 195 Stat, not holding water long enough

 

Definitely add a shroud, your need to pull all the air you can thru your radiator.

 

typically production model cars up until the late 70's with A/C came with a larger radiator.
you may need to consider this once you have tried all the other solutions.

 

I don't see anything wrong with 210 with the AC on. You are putting an additional load on the engine plus you are dumping heat in front of the radiator. A shroud may help low speed running temperature. But if it is running 210 going down the road at 45 mph or above, I don't think the shroud will do much.

Also someone mentioned going to a 195 thermostat. Thermostats only affect minimum operating temperature. Once a 180 or 195 stat is fully open they have no effect on max operating temperature.

 

You may need an electric pusher fan to help with air flow .

Mac systems develop a lot of heat that needs to be removed for the system to function correctly .

 

Generally speaking a condenser coil can add an additionally 8F - 20F temperature to the air exiting the coil depending on the heat load, etc. Heat load of the condenser is equal to both the compressor shaft hp plus the evaporator load. The higher the air inlet into the condenser, the higher the compressor discharge pressure which means a higher refrigerant temp which equals a higher air temp leaving the condenser. Spacing the condenser further away from the radiator is something I never heard of in all my years of experience in mobile AC design. Is the AC system properly charged. An over charge of refrigerant will result in higher discharge pressures which will result in higher air exit temps as mentioned previously. This type of condition doesn’t really rear its ugly head until ambient temps become high (e.g. in excess of 90F). As others have already mentioned a shroud or ducted fan will perform 50% - 100% better than one in an unducted scenario. Air will be more evenly distributed over both the condenser coil and radiator increasing heat exchanger performance and avoiding hot spots and dead zones on the coil surfaces. Another little trick is to insulate the AC suction/low pressure line as any heat absorbed lowers overall AC performance, increases suction pressure which results again in higher discharge pressure which equals hotter air exiting the condenser coil. If using a GM type AC system with a suction line accumulator (big aluminum canister), they should also have a foam insulating sock for it to help with heat absorption. Also, it’s been my experience with military cooling systems to see about a 20F delta between air temp entering and heaving the radiator, so it would not be uncommon to see 210F air temps exiting the radiator if air entering the rad was 90F.

 

This is reason I love the HAMB, a lot of general knowledge from peoples personal experience and also an expert in just about every field of the hobby to really break things down and give excellent answers.

 

Make sure all the air is going through the radiator, and not around it. Block any gaps or holes, and maybe even fab a deflector to keep air from going between it and the hood. Air, like water, will go the path of the least resistance.

 

Move to Arizona, it'll be 230.

Seriously...unless you're having issues with fuel boiling because of the higher underhood temp, you'll be fine running it as is.

 

The Condenser should be 1/4 ln in front of the radiator. There are some Condencers that are too dense and block air to the radiator. Put paper with writing on it between the radiator and the condencer if you can't read it that is causing you over heating going down the road.

 

A shroud is a must, and a thermostatically controlled pusher fan. It will stay at 180 no matter how hot is is out.

 

I prefer the 210 over the 180 on a SBC anyway.
I had a SBF that cooled better with a 195 thermostat than it did with a 180.

 

There is a reason why cars today have a temp gauge without the numbers. I was out with my buddy one night and his '87 Vette was running at 217. This was on a cool night.

 

If you are running a standard 4 blade mechanical fan that will not cut it. You need a five or six blade factory type fan with SEVERE duty fan clutch if you have the room.

 

Think you've been given the answer by all the above. 1/2" for the condenser is fine, shroud covering 1/2 of the fan blades, 6 blade, or 7, steel fan w/ clutch, insulate l.p. line, even into the car, and don't overcharge it. One think not mentioned (that i am guilty of) is a cheap evaporator if this is an add on, some of them just won't do the job like a good quality unit.

 

You will loose A/C cooling if you move the condenser forward, they need all the air you can pull through them plus some ! When adding a fan shroud, add one to the front also so any air entering the radiator must pass over the condenser as well, if it bypasses the condenser, your A/C will not cool at low speeds.

 

A couple things to consider, when you add a thermostat you are adding a restriction in the cooling system , Take it out you won't hurt a thing. I would run it without a thermostat. And if you add a clutch fan you will slow the fan speed down over having a mechanical , meaning less airflow. I have never seen a motor where the water is running through it to fast to cool it off !

 

how about a few pics of motor/ front of radiator, etc - details on motor -size/age of radiator? -etc

 

They get all this shit off the internet !

 

Basically, we need to know whether the 210 is at idle, cruise, or both. Also, you mention that the A/C was "in place" already ......just not hooked up. By "in place", do you mean it had a belt turning a pulley, or just simply bolted to the engine? The reason I ask is I'm wondering if you made any change in your belt arrangement. Also, was the condenser already in place when you were running the lower temp?

What I'm getting at is that if all the components were already in place, then the only actual change made was warmer air being provided to the radiator after it passes thru the condenser. Just need a few more details to try and sort this out.

 

Is the AC on your 55? Is the radiator in the stock position for a V8 or the 6. A little more info or photo might help. I had to speed up my water pump, use a hi-flow thermostat, 6 blade fan, fan shroud, and a radiator support to hood seal. Perfect now in any weather.

 

Thats an old argument. The truth is that as long as you have an uninterrupted supply of cool water to supply to the motor, you are correct that the speed of the water (as long as its not too slow) will make no difference.
The caveat here is the uninterupted supply of cool water

Where the problem lies is in a closed system like an automobile engine, there is a difference in the ability of the water to absorb heat from the motor.............and the ability of the water to give that heat up in the radiator. More specifically for the air to absorb the heat thru the aluminum/brass radiator.

If the water is moving thru the radiator "too fast" it won't be cool when it returns to the motor and absorbs more heat. So the question then becomes......is the water moving thru the radiator too quickly to give up its heat OR is the radiator too small for the amount of heat that needs removing.

Now if you make a radiator larger, water moving at a specific speed will take longer to pass thru it.
If you keep the radiator small, then you must keep the water in it longer to give up the heat.

It kind of a play on "semantics" because if there was a way for the water to travel more slowly thru the smaller radiator, it would eventually give up the excess heat.........therefore its traveling too fast thru that size radiator.

Again, it just a matter of how someone wants to look at it. Semantics

 

Wow…. Lots of advice and ALL of it is appreciated. In response to multiple suggestions and questions:
- yes, it’s the 55 Chevy I’m working on.
- radiator sits forward of the support
- engine is a 300hp, 350cui, flat tapper.
- compressor is a new GM R4
-fan is a stock GM 5 blade clutch fan
- Freon is not over serviced and probably a little low. I’ll verify pressures a bit later.
- The (not this particular one) compressor has been holding the belt/ pulley position for the past few years, but had never had the clutch engaged.
- the condenser was mounted months ago, but not plumbed.
This car is now and has been for 38 years my EDD ( every day driver). It was primarily built and maintained via the local salvage yards, but now the engine and AC are all NEW stuff.

After all the input,
-I will leave the condenser where it is and not increase the gap.
-I will insulate the suction line more betterer .
- I’ll experiment with a home made shroud

I took it for a spin this morning and it was actually doing better at ~ 190, but the temp outside was probably mid 80s. The heat index yesterday and later today is for around 105-110 degrees. I’m thinking that may play a pretty significant roll. Welcome to Florida in summertime.