Improving airflow
 

So let me start off by saying my car does not overheat. Going down the road it runs 173-177. Sitting still with the AC off it never goes over 183 even when its 95 degrees out. Here is the situation involving AC. If I get stuck in traffic or idle with the AC on the temp creeps. I posted about this before but I have found the "problem" I just need to see if I am out of options. Yesterday I got stuck in downtown Clemson and it creeped up to 197 over the course of 20 minutes. I turned the AC off and it immediately stopped and went back to about 188 before I started moving again. When I got stuck at the other end of town same situation with AC but this time I used my foot to raise the idle to 1200-1500 and it stopped creeping. So it is obviously an airflow issue. I have the 15 inch Cold Case HD radiator. 18 inch clutch fan and Hayden severe duty fan clutch. Have I exhausted all my options or can I do something to make the air flow better to stop this totally? A bigger fan will not fit in that shroud and the shroud is sealed to the radiator with strip insulation

pulleys possibly, raise roationale speeds of water pump and fan that way..

i dont know if there is a idle stop solenoid that is universal but when A/C is engaged it raises idle speed

Stuck in traffic with A/C on for 20 min and creeping to 197 does not seem like a problem to me. That said, I was having a similar issue with my wife's 68 FB (temp would creep to 205+ with A/C on in traffic during the summer months) and addressed it by installing a small pusher fan directly on the condenser (wired so it operates when the compressor is on).

Question for the OP.
When you turn the AC on and your idle rpm drops due to the drain on idle Hp, what else would you expect to take place?
1) you have added another load to the motor.

2) with a engine driven fan and the drop in idle rpm you have cut back on air flow.

3) you have slowed down the water pump and the circulation rate.

As posted I would at least add a solenoid that that kicks in when your compressor does to up your idle
speed .
Hint, if your AC stays somewhat cold even though your idle has dropped, and you have some temp creep then that’s a sign that your air flow rate is not too bad, but at idle your water pump’s circulation rate
could be better.

What's your idle rpm? With a manual trans you could raise it 100-200 rpm with no ill effects and see how that works out. Or an A/C solenoid like others have said.

My idle rpm is between 850-900. Turning the air on has little to no change of idle speed. I guess a fan on the condenser is worth exploring but won’t that obstruct even more radiator air flow when it’s off?

First off in my opinion you don’t have a problem here to fret about and yes installing another fan will help at idle, but likely block off needed air flow at road speeds even when not powered and free wheeling.

Bottom line, at idle even 215 degrees your motor is not too hot and your coolant mix since it’s under pressure is not boiling.
Stop thinking that such temps are death for a engine!

The fan I'm using is pretty small, and the car stays at around 185 or so when the A/C is off, even on the hottest days here in Arizona. It works well enough for us, though your situation may be different. Having said this, although the fan and additional wiring is basically invisible unless you look for it, I prefer simplicity, and so I'll revisit it at some point when move my other projects forward.

yeah, I agree with this. The only reason I added a fan is because my wife drives her bird and I wanted an extra margin of safety...she doesn't monitor the gauges like I do.

I agree it’s a non-issue…to a point. I can just turn the air off and it stops dead in its tracks and then goes back down but isn’t the point of AC to have it on when it’s hot as hell.

I think the point being made is that even a (temporary) 215 temperature is nothing to worry about, or a reason to turn the a/c off. The factory overheat warning light didn’t come on until 240-245 in these cars, and the Pontiac engineers didn’t consider anything under 260-265 as engine damaging temps.

Run it and stop worrying about it getting above 200 degrees with the A/C blasting.

Even 220 isn’t that bad.

Once it hits 220 or 225 then shut off the A/C for a while.

197 degrees is nothing.

Remove the gauge, install the factory temperature light, and enjoy your car worry free for the rest of your life.

My '67 has the light and it never runs hot or overheats. :)

Cold Case does make a 17-1/2” Severe Duty radiator with twin 1-1/4” tubes instead of the 1” tubes.

Unfortunately you didn’t either source a core support that accepts the 17-1/2” factory air conditioning/Heavy Duty cooling option radiator, or convert your standard core using the bottom piece offered by Cold Case or Ames.

Every little bit helps, especially with the early A-body cars with limited radiator area and down flow design.

In order to use the Severe Duty radiator in my Le Mans with factory air conditioning I had to use the ‘66 upper hose and thermostat housing. That radiator has the more efficient upper inlet on drivers side unlike a ‘64-‘65 radiator.

That’s what I have.

You said you have a 15 inch Cold Case HD radiator in your original post.

So which is it?

I am using the 66-67 style drivers side inlet is what I mean. It is the smaller core (15 inch) but the inlet is on the drivers side. That was the first solution offered me by Cold Case when my first engine wouldn’t cool at all.

197° in traffic with the AC on? Pfft that's not a problem.

Find a smaller WP pulley. It'll increase the air and the coolant flow.

Raising his idle speed will provide the same result as the above and consume less power when the vehicle is moving.

Most folks don’t want an idle speed of 12-1500. Even the factory put smaller WP pulleys on the A/C cars vs non A/C cars.

And I’m sure it’s likely the best radiator they could have sold you considering the major constraint being the standard 15-1/2” core support. The coolant flowing diagonally is a little better design than the original ‘64-‘65 with both hoses on the passenger side.

When I called Cold Case they recommended the Severe Duty twin 1-1/4” tube radiator that only came with the ‘66-‘67 inlet and outlet that only fits the 17-1/2” core support. I don’t think the Severe Duty radiators come in any other configuration.

Unless you’re into swapping core supports or upgrading your current one to 17-1/2” you already have the best radiator for your situation and honestly it’s not really working all that badly.

Agree 100%. He's chasing ghosts.

Thank you. I'd be mildly unhappy with an 850--900 rpm idle, let alone raise it higher.

There’s a good reason why the air conditioned cars all had a smaller diameter water pump pulley.

I forgot the reason….. ;)

b-man, do you have the part number for the Cold Case Severe Duty radiator?

GPG38AS

I checked their website and saw GPG38A but I’m thinking the S added to the part number is what designates Severe Duty with the 1-1/4” tubes. Keep in mind my application is for automatic transmission.

https://www.coldcaseradiators.com/pr...tor?sku=GPG38A

Call sales at Cold Case to confirm but that should be the same exact one I purchased.

When I was 20 years old and my GTO was a daily driver, on really hot days ... I'd just put it in neutral when I came to a stop, usually the extra 200 rpm or so was enough to keep it cool with the AC on.

And, if an automatic transmission, helps by not loading the convertor which builds heat.

Hey gang, he’s got a manual trans !!
I can’t see why an increase of 150 rpm is an issue to reset the carb or FI to for just the hottest summer months.

Maybe even just 100 rpm more then his current idle speed will give him the non temp increase he’s looking for.

Maybe his problem is being caused by hot air from the radiator being recycled back through the radiator when the vehicle is stationary. Our cars were not designed to sit in today's traffic. New cars are engineered to prevent or at least minimize hot air being recycled through the radiator.

The easy solution is to place a piece of electrians tape over the temperature gauge display! ;)

Jon

His problem is the digital readout. You can watch
the temperature rise degree by degree. It went up.
It went up. It went up. Cars were never meant to
stay at a fixed temperature, and using the AC on a
hot day is gonna make it move. Can't remember
which desert we crossed, but it had signs warning
against using AC. I wonder why... :confused2

Do you have a fan shroud?
My thought process is to increase fan efficiency at lowest rpm.
An idle speed ‘booster’ solenoid is how engineer's combated this issue…what do they know 🤔
✌🏼

From what you said, it sounds like you're not worried so much about the 197 temp but more worried about the fact it may keep going up until you overheat. If that's the case, just test it. Get it fully heat soaked then return to your driveway and let it sit and see what happens. You may find that it will reach a limit and not overheat.

I don't have AC but here's what my car does. I have a OEM style radiator 180 deg thermostat and a flex fan (not sure of the diameter) and a factory shroud. The motor runs at 180 at all times while moving at any speed. At a stop, it will climb up to about 190 fairly quickly. But, it never goes higher. I almost never have to stop for more than a couple seconds at a stop sign but every now and then there's road work going on and I may have to stop for a couple minutes. The first time I watched my temp climbing up quickly I got a bit nervous. But then once I got moving again it came right down. So anyway, I tested it like I described and it climbs up to maybe 190-195 and just stays there. Doesn't keep climbing. So give it a try and see what happens.

Also, are you running vacuum advance? If so, is it connected to ported or manifold? Manifold will run cooler at idle. Also, depending on your driving conditions, radiator fins can get clogged up with bugs and debris that can affect cooling especially at a stop. Probably not the case with your car but you never know.

Exactly! I am wary of finding out what my upper limit is.

By staying with the 15-1/2” core support you limited yourself to not only the smaller radiator with 1” tubes instead of 1-1/4” tubes but you’re also missing out on the larger 19-1/2” fan.

If you want the additional peace of mind and cooling capacity of the bigger more efficient large tube radiator and 19-1/2” fan plan on spending whatever it takes to replace or modify your core support and upgrade your cooling system.

It’s not a big deal finding out what your upper limit might be, don’t be shutting it off at 197 let it hit 220 before you shut it down next time. 20 minutes sitting in traffic with the air conditioner running and only hitting 197 seems like you’re doing fine to me.

That's the source of your stress right there! Man, have I felt it. You could correlate my heart rate to my water temp gauge. Test it and see. Maybe (probably) it's fine. If not, you need to know,

If I buy a condenser fan do I want it to push or pull?

An extra fan is no magic bullet. If it
can't move at least as much air as
your existing fan I'd wager you just
created an airflow restriction.

Only a pusher will fit if you’re concentrating on the condenser - though that will have to be two fans to get full coverage. If you want to explore, see if you can adapt an idle solenoid that engages when AC is on. That be said, I think at this point, without testing upper limit of your temperature, you’re looking for a solution to a problem that doesn’t exist.

Upper limit so far is 210. Gonna put a box fan in front of the radiator tomorrow and see what happens

So that's getting a bit warm there but not overheating. What's your timing situation, base and VA setup?

Before I completely abandon this pursuit does anyone know if a 7 blade fan is that much better than a 6 blade? I have the Derale 17118 fan with a Hayden severe duty clutch. I was told the 73-87 GM 454 fan will fit in that shroud and it’s 7 blade. Anyone recommend a better fan than that?

I got the 17019 for my T/A and it cured all of my american idle air flow woes for good...

https://www.summitracing.com/parts/DER-17019

I drove it today and at 78 degrees outside with air blasting there was very little temp creep. I contacted Derale and I have the only 18 inch clutch fan they make. I just need a tiny bit more CFM to stop this. Does anyone have a recommendation for the absolute most aggressive 18 fan I can buy?

Find a 7 blade fan, will move more air due to more area to grab air.

You didn't mention which thermostat, I'm assuming it's 180 deg F. In regards to the 215 deg F operating temp, if my home thermostat was set to 70 and the AC couldn't regulate temps any better than 35 deg above the thermostat set point, I'm thinking I may have an issue.

Did you adjust the cut-in temperature of the fan clutch? Does it roar when you blip the throttle once temps have gotten up there?

Keep this in mind with a 7 blade fan.

Even when it’s freewheeling at high road speeds it WILL block off air flow from passing thru the radiator than a 6 blade fan.

You may need to find a balance point where at high road speed a big throttle openings ( IE high Hp production) you might find the temp creeping up on you.

You might find that a temp of 215 at 4500 rpm is more un-nerving then 215 degrees seen at 800 rpm.