Technical Running hot with A/C

Hi guys, what we have here is a "32 Ford 5 window running a 375-410 HP SBC. We have Walkers biggest radiator, their shroud for it, and a Hayden 17 inch flex cool fan. The fan is approximately 1 to 1 1/4 inches from the radiator. The engine has a Zoops high riser water pump housing that runs a Chevy 6 cy. water pump. That item is a Tuff Stuff pump and does have a cav plate on the impeller. The thermostat is a Robert / Shaw 180 degree. The pulleys are 6 1/4 lower and 5 1/4 upper. Almost 1 to 1 I suppose. The temp sender is on the top upper left side of the intake. The tank is the typical over-flow at 14 inches in length. Oh yeah, the Zoops has an air bleed screw on top of the water pump area. The A/C system is from Vintage Air. Everything is properly plumbed per manufacturers and we all know how they are.

What the situation is that I can run all day, local stop and go traffic or the freeway, at 180 degrees and never get over that temp. If I turn on the A/C after a while it will gallop up to about 200 degrees and pretty much stay there. Cannot tell if the thermostat is functioning as it should. Running down the freeway, it will run at 180.
So do we have any ideas? This is actually driving me up the proverbial wall trying to figure this one out. I have been told to change the thermostat to 195 and my problems will go away? Arrrgggg Oops- - we are running a 16 pound cap!!

 

200 isn't too high while running the A/C. If you have a 14 PSI cap on it I wouldn't sweat it.

 

I'm running a 16 pound cap- - - per Walker recommendation.

 

Make a shroud for it, with the opening about 1-1 1/2" larger than the fan diameter, ad the fan blades half in the shroud and half out, and you will most likely solve your issues.

 

I didn't think much of the flex fans,I prefer the 17" steel fans like this one from Summit.



The only other things that is different on my deuce is I use a 195 degree thermostat and a 14 lb. radiator cap.

BTW, I don't have a shroud and the car never runs hot. HRP

 

I wouldn't sweat 200 with the AC on , not at all.
But flex fans aren't the best.

 

If it runs at 180 on the freeway with the ac on, you either have an air flow or engine speed problem. Engine rpm changes fan speed assuming mechanical fan and water pump speed. Driving at higher speeds forces more air through the radiator. Sometimes the flex fans won't pull enough air as the blades flatten out. Try running in a lower gear in town or see if the temperature goes down by reving the engine up while sitting still. You might need a non-flexing fan.

 

I agree with engine man about the air flow problem at lower speeds. Ad an electric fan that is triggered to come on when you turn on the AC or is thermostatically controlled to come on when the engine temp reaches 200 degrees. I think this will solve your problem

 

The condenser is a heat exchanger, it is going to raise the temp if its in front of the radiator. if it run at speed and in traffic at 200 you are golden, especially in Texas.

 

Does your car have an automatic trans? If so is the trans cooler in the radiator? If yes move it to a stand alone trans cooler not in front of the radiator. That will make a world of difference.

 

The condenser is in front of the radiator.
Yup----Thought I'd change the thermostat to a 195 and see if that helps -- sort of. And yup--we're in Texas!! Amarillo like!

 

The car is a 4 speed- - - Super T-10

 

I have a non-flex fan -- - its the Walker one and it didn't pull enough air around town. There-fore we went to the Hayden flex to pull the air while in town.

 

It does have a shroud and with the fan being at 1 to 1 & 1/4 inches in, its pretty much sits about half way in!

 

Your fine, 200 is nothing. This is normal with a A/C Hot Rod.

One thing folks need to know is that the junk gas we get makes our engines also run hotter, and there is nothing we can do about that except run non-ethanol if you can.

 

You're okay at 200 with the A/C on. Drive it, man!

 

I dont like to ever see over 210 on a carb equipped SBC.That being said a 20 degree difference from running the AC is very good indeed.If it really doesnt get over 200 on a hot day with the AC on you are in good shape.HRP is absolutely right about the big paddle fan,I went through 6 different fans on my 406 sbc and ended up with the fan he shows in his illustration and got a good 20 degree temp drop over all other types.

 

This is your answer.

 

Ya, the fan HRP recommended is what I usually try to use. Not sure about the Hayden flex fan, but several of the Flex fans have a sort of "closed" center that hampers airflow with their use. Unlike some, I don't mind using flex fans, I just make sure they are new, and of an "open" center design. some the more aggressive types work very well.

The other though that comes to mind, have you check the outer diameter of the fan hole in your shroud? If the hole is small enough that it fits tight all the way around the fan, again it tends to hamper the airflow through the fan and shroud. In other words, it will draw the air into the condenser/radiator, but not efficiently let it back out. That inch to inch and a half I mentioned earlier seems to be the magic number.

I build hot rods and install A/C in hot rods here in Phoenix, I'm pretty good at cooling stuff off...

Oh, and while I agree with a lot of these guys about 200 not being the end of the world, I too would like to see you back down in the 180 range. Especially if you have no other choice but to run ethanol fuel, as it tends to boil right at 200...

 

Just to define "closed center" vs. "open center" flex fans here are some images.

This is what I call a "closed center" flax fan, and this one happened to be a Hayden unit... Terrible! These flow air at the tips, but virtually nothing in the center of the fan. These also have a tendency to build a "wall" at the outlet of the fan shroud when you are traveling at speed, which limits how much air can leave the shroud.


This is what I call an "open center" flex fan. Much like the rigid fan HRP was talking about, this one promotes an even airflow all the way across the fan's diameter. Much, Much, Much more efficient.

 

That's interesting, after a careful scrutinizing of the temp gauge, it would appear to be running at 195 degrees. I don't particularity like 200 but then with today's gas and the sort of cars we all build, 200 would appear to be a decent temp?
Having an open wheel car with the engine totally exposed does make for some compromises or so I'm told. Thanks for the info. I'm going to change the thermostat to a 195 and hope that will function a little better.

 

The fan as currently explained as an "Open center" is exactly what I'm running. Its like the Derale and Hayden flex fans! By howdy they do pull the air. That other fan is exactly what Walker sells and recommends. Didn't work for my application so it hangs now on the wall with some others. I had a "40 Ford running a 327 with a Walker and was having some cooling issues. They went away after covering the top of the inside grille area and going to the Derale Flex fan. Thanks for your info.

 

I resolved the air flow with a much better fan, I used the Hayden Flex fan that can run to 10,000 rpms and is an open center type. At any rate, the air flow is solved at running around town because that fan really does pull the air thru the radiator and condenser. There is an inch all the way around the shroud to the fan. Thanks for the info.

 

I have used the flex type fan (open center like 2nd poc) for many years.....i pulls ALOT of air. It will flex flatter only when you step on it like hot roddingx up through the gears or standing on it coming into traffic. An electric fan set up w thermo control is the ticket for A/C in town. Although 200 and stable aint nuthin....normal

 

Have you checked the timing lately????maybe retarded a little too much

 

It makes sense that the higher rpm rated fan would be a little stiffer. I'm glad you got the problem solved and posted the solution. Could you post the part number for others who might need it?

 

Thanks for your input- - - all the opinions are really helpful!

 

Thanks for your input- - it all is very helpful!

 

The engine is tuned for what it is. Its all right on the mark, it just purrs and runs like a scalded cat! Thanks!

 

I stand corrected on the brand, it looks like the Hayden but its a Flex-A-Lite puller 17 inch, # FLX-1317. Got it from Summit Racing. When using it, need to ensure that it sits half-way into the shroud. Might end up buying a ton of spacers to get it right.
Thanks for all the opinions and suggestions, they have allayed my fears and offered up a couple of ideas.