[duke's68]

The good news is I got my Vintage air set set up installed and working, The bad news is I can't use it cause the car over heats terribly when it is on.
I have an aluminum headed 383 with about 9.5 to 1 compression. Mild cam. A very streetable engine. 4 core copper radiator with a stock shroud. Clutch fan and no underdrive pulleys. 180 thermostat, hi flow water pump. I never had any problems without the ac.

I have the Gen 2 super cooler. The heater lines run through a servo operated contol valve. The valve gets shut when the AC is on. If I turn on the the AC( valve shut, compressor on), the car starts creeping to 195 -200 in about 20 seconds. then up to 220 230 in about 90 seconds. The gauge will acutally fluctuate very rapidly between 220 and 230. I think the coolant must be boiling and causing that. The temp will also raise up fairly quickly with the heater control valve closed and the ac off.
As soon as it gets hot I can turn on the heater and have the temp down in about a minute. I though I had a bad thermostat, but that proved to not be a problem. I tried a new brand with the same problems.

The car used to run just fine no matter how I had the control valve positioned. All I did different was run the lines for the AC. I had the condensor installed and everything in place before. I just don't see how the engine could get so hot so quick and then cool down just as rapidly????
I need help

[Everett#2390]

Usually, one wants the water pump to be driven 30% faster than crankshaft. I would use a Mr Gasket Hi-Flow thermostat.

If you turn off the engine when hot, listen for boiling. Water girgling, the sounds of a bad radiator cap, or one of not high enough pressure rating being used. I have on my dually a 22# cap to prevent boiling. Radiators and heater cores are factory tested to 50#.

If all else fails, you might try a large flex fan. The addition of a condenser ahead of the radiator, will add to engine coolant temp by 15-20*F.

Your A/C compressor compresses the freon, this heats freon up expotentially, the condensor must cool the freon gas to turn it back into a liquid freon. Alot of heat is given up, this heats up the ambient air temp drawn through by the fan.

[duke's68]

I just put on a new 16lb cap. It didn't make a differnce. I am going to replace the clutch on the fan. It is very old and maybe isn't working properly. Is there a way to check them?

[HOTRODSRJ]

Wait......you can't ever determine even if a NEW clutch fan is working.

Try one of the heavy duty flex fans from Derale. Go to http://www.derale.com/flexfans.shtml and select the biggest fan that will fit....probably an 18". These fans take less hp that yours now, and pull more air. No clutch to worry about and available from Summit racing for under $60. YOu will need a 1" or 2" spacer depending on shround and radiator.

[choptop]

Jonathan you have me scared to death now...I was saving up to do Vintage air as my next project in a couple of months! Now I'm not so sure what effect putting the evaporator core in front of my radiator will have.

Can you still get the car to overheat with the a/c turned off? Maybe this is an airflow issue and swapping out the fan might help. Are you getting a lot of underhood heat from the headers? Maybe they are contributing to heat soak...

[ 06-03-2003, 05:13 AM: Message edited by: choptop ]

[HOTRODSRJ]

This is a classic example of why airconditioning cars come with extra cooling capacity by virtue of bigger radiators, bigger fans, etc from the factory. You have to consider the whole system and upgrade accordingly or you will be living with a system that will not cool correctly with your addition of air.

Anytime you add air you should ABSOLUTELY upgrade the radiator to larger capacity model either with more shear size or switch to aluminum media which is far more efficient than copper/brass/solder ones! Fans too. Sometimes you can get by with what you have, but it's a risk in demanding environments such as long traffic lines or high ambient temps.

It also sounds like you have added considerable more hp to your engine which also requires more cooling capacity than before...even at idle and slow speeds.

In this case, more airflow may remedy this problem and then maybe not. An alternative is to select a location if possible for the cond coil to live with a separate fan. In most cases this is difficult if not impossible. So, fooling with radiator caps, thermostats, higher flowing pumps (which I recommend as well) will not help unless you can unload the heat at the exchanger which is pure airflow and capacity issue.

If you are willing to really improve the efficiency of the system by adding monster air movers such as twin Derale or Spal or Windstars or a Mark VIII fan, then you may get by. The Derale Heavy Duty flex is a good investment too. I have it on my 69 ragtop, 400hp+, air, PRC raditaor, in Atlanta heat and traffic and it cools great!

The other sure fire solution is to buy an alum radiator at www.streetrodstuff.com/Products and upgrade the airmover and I know it will work in Death Valley.

Good luck.

[duke's68]

I aggree with you on updating the entire system when doing upgrades. I thought I would be ok with what I had.
I did upgrade the radiator. It is a 4 core. I also added a high flow water pump. I believe the problem lies in the fan. Today on the way home it overheated (205) in traffic without the ac on.
Something else is happening that is really wierd. I can close the heater control valve and it overheats much quicker and much hotter. With it open it takes alot to get it to overheat. I realize that opening the valve allows the water to flow across the heater core which is basically another radiator. I don't have the fan blowing across it though so I don't think it would make that much differnc, but it surely does.
I am pretty sure I am going to order a mark VII fan from what I have heard. What is the best set up? I have heard about the windstar fan. Where do I get this one? How much? whart year?
Thanks

[HOTRODSRJ]

Hey Duke.....wasn't pickin on ya for any reason but even the four cores for these cars were/are "on the edge" and certainly by adding the "beastly" 383, if it makes the hp that I think it would, would be a push for that radiator....especially with air and any hot temperate region. I had a 65 Impala big block (that did not make the hp your 383 makes) factory air when I was a kid for my first car and it didn't like the summer months in traffic either.....straight from the factory with the four core!

You're on the right track tho.....raise the efficiency of the heat exchanger by increase airflow and improve the whole system!

So, the Mark VIII is a behemoth, and the Ford Windstars everyone seems to get new or from junk yards. I prefer the twin Spal 11" fans...or if you need more the twin Derales ( http://www.derale.com/electricfans.shtml ) offer some 4000 cfms of help! Check out your dimensions and have at it.

[click]

Just a sidebar to the over heating issue. If you are on the edge of your cooling capacity, keep in mind that the radiator system does about 60% of the cooling of the engine and your oil does about 40% of it. If you are not using a good quality 100% synthetic oil like Amsoil or Mobile One, you are not getting that extra cooling capacity of the oil.
Its not a cure all for mechanical problems if there are any, but syn's will more efficiently move heat from your engine to the pan where the moving air slides that heat away.
Its worth a try and in the process you gain mileage and gives you a little more HP as well. An added benefit.
Good luck
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[kwissman]

Jonathan,

My camaro used to overheat in austin also. I had a bb truck radiator, and did not know what to do. I bought 2 bottles of redline water wetter and changed the Antifreeze to water mix to mostly water and it stopped overheating. This might be a cheap quick fix.

[duke's68]

Tell me if this makes since. I said that it overheated real quick with the AC on and the heater control valve closed. So I tried running the AC on with Heater control valve open. AC didn't work worth a damn, but it never overheated.
So, I disconnected the heater lines and put a loop from the manifold to the waterpump, so there would be a continuous flow of water just like if the heater control valve was open.
Problem Solved!!!!

I don't get it. Close off the flow on the heater lines and the temp freaks out. I mean, go from 180 to 225 in about 2 minutes. Now that it is bypassed I can sit at idle with the AC on and it sloooowly creeps up. Which means I do need more airflow, but now I can use the AC. Why on earth would it react so quickly with heater lines blocked off??? One of my buddy's suggested maybe I have a reverse rotation pump on there. Maybe.... but wouldn't it cool like like crap all the time. I have 4000 miles on this motor with minimal problems with overheating, until now. Any ideas????\

[Everett#2390]

You might have a reverse rotation pump, need to check this out.
Another idea would be the heater hose routing, 5/8 to the intake crossover & 3/4 to the water pump.

[Rob.Canada]

Hey Duke,
I have 68 SBC with factory air, also had many AC cooling / overheat issues,

Factory 3 core rad, AC running, Cold air was poor, installed water valve, vacumm closes valve on MAX COLD, Good Cold air,
Run the car hard and it would overheat big time AC on or OFF, pulled the thermostat and gutted it, Run just the ring, still would heat up but not as bad as with T-Stat.

Got new 4 core BB rad, used SB shroud and stock clutch fan, with gutted t-stat, runs less than 150 degrees, obvious the rad looked good, thought it flowed good, but the new rad made world of difference, It hasn't got over 75 degrees around here but at 70 degrees outside with AC on the temp gauge climbs to about 160 - 170.
So I get a thirty degree increase in coolant temp with AC on.

so looking at your problem,
Rad is new, should be okay.
Clutch fan is useless after 20 mph, so it can be elimanted as problem,
Bypass the heater core, flow through the heater hose and no more over heat, but overheats when you shut off this flow.
The water pump does not create pressure, it only moves water, it cannot move water, if there is no place for it to go,
Since you shut off the flow to the heater core engine over heats,
Two things the t-stat is stuck shut, and not allowing water to flow from engine to rad, or the water pump is turning backwards.
Cheap diagnosis is pull the t-stat and cut out the guts, problem solved install new T- stat.
still the same, look inside the rad engine running, which way does the water flow, it should be coming from the drivers side across the rad, and it will be moving fast, no flow or poor flow, replace the water pump, stay with a stock pump, no need for a trick unit, the stock pump will be more than adaquate.
Good luck and lets us know what you find
Rob.

[DjD]

I think Rob is onto it!! What hi flow water pump are you using and what brand of thermostat? Stewart pumps I believe require a Mr Gasket (Robert Shaw) stat with the bypass holes drilled in the housing if my memory serves me correctly. I run a stock flow water pump and have my heater output and return plugged and have no problems.

[duke's68]

thanks guys-
I will look into the water pump. I have Jegs hi flow pump. I'll watch the flow of the water in the radiator and get back to you.

Thanks for all the replies...