Rad vs A/C Condenser

I have a 350 SBC that I just rebuilt, a new rad, and new A/C unit. The rad has the electric fans (2 - 12") behind pulling the air. I can put paper on the grill when the fans are running and the paper stays there. I have tried a 160, and 180 thermostat, the thermostats do open and I do get water flow. I over heating problem is both when I idle and when I am on the hiway. I have tried Wet Water, and tested the cap.

I just took the grill off of my 1936 Chev and noticed that the condenser is 12”w x 22”h and it covers my rad that is 17”w x 22”h. The condenser covers nearly 2/3 of the rad, so I was wondering if that could be the problem The Old Air Products installation instruction says the condenser should be installed with ¼ to 3/8” space between it and the radiator, being careful that they do not touch. I would think this would stop the flow to the rad and cause over heating. Would I not be better off to separate the condenser from the rad and put a fan on both? Have the Condenser and a fan behind it and then the rad with a fan behind that?

Try the fans in front of the rad pushing the air thru to cool the rad.

It's a pretty common problem with early cars like your Chevy and others like 39-40 Fords. The shape of the front end sometimes doesn't cause air to go through the radiator, but it gets deflected around the front instead. Another problem can be that the air in the engine compartment has no way to exit. When you put a big V8 in an engine room that originally held a smaller 6 or flathead 8 it tends to block some of the airflow in and out of the engine room.

Puller fans are much more efficient than pushers, and a shroud is a must so it directs the air clear across the entire core. A high quality fan is also much more efficient than the Autozone types or even the ones sold by most places like Summit. I like SPAL and I have seen good reports on a Lincoln Mark 8 (I think) fan setup.

For a cooling system to be efficient all the components have to work together. You need good airflow both when sitting and when moving, and good water flow also. Your AC unit is not helping, but lots of guys are running air and having no overheat issues.

You mention two 12 inch fans. Believe it or not, one 16 inch of good quality will out perform those two fans. And I stress again, make up a metal shroud so the core is sealed and the air has to be pulled clear across the face.

Don

Is it actually boiling over or is the gauge just reading excessively high? It is reading over 215 and I stop as I do not want to damage the engine

Are you spot checking with a heat gun. No I am using 2 different temperate gages

You just rebuilt the motor, did you replace the water pump? Yes
Correct rotation? I assume so but will check. It rotates like the other one in my truck.

Maybe try a 195* stat, possibly hot water is circulating so fast with the lower temp stats it doesn't stay in the rad long enough to cool. I have tried a 160 and a 180. I have a 195 but I just hear of a high volume temp stat that I thought I would try.

The shape of the front end sometimes doesn't cause air to go through the radiator, but it gets deflected around the front instead. I will look in to this. As the fan is pulling the air, should I have a shroud in front of the rad so all of the air must go through the rad/condenser?

Another problem can be that the air in the engine compartment has no way to exit. I have the sides off of the engine compartment, so the air can get out.

You mention two 12 inch fans. Believe it or not, one 16 inch of good quality will out perform those two fans. I am wondering if I should put a 16" fan and shroud behind the rad and move the condenser ahead of the rad and put a 12" with shroud behind the condenser?
And I stress again, make up a metal shroud so the core is sealed and the air has to be pulled clear across the face. As the fan is pulling the air, should I have a shroud in front of the rad so all of the air must go through the rad/condenser?

Condenser and trans cooler belong in front of the radiator. Electric fan should pull from behind the radiator. Be sure to check that the fan rotation spins the blades to pull!
Water pump rotation.....Conventional rotation for typically older chevies is clockwise when looking at the front of the engine if it has v-belts. Newer with serpentine belt will have a counter-clockwise rotating water pump and pump-mounted fan (if equipped)
I don't think you'll know which rotation pump you have by looking at them unless comparing with a new pump (maybe not even then!)
Contrary to popular thought, your engine will ALWAYS run cooler if you take out the stat, which I recommend you try just to see what the engine produces for natural temperature.
I was told (and didn't believe) by several mechanics that one in three new thermostats are defective.... I started believing when I installed a new one that was bad.... I now heat a cup of water in the microwave to the correct temperature (checked with thermometer) and drop the new stat in to see if it opens before I even bother installing it!

I checked the specs on the Hayden fans and the 16" fan 3700 has 1400 cfm, the 16" model 3710 fan is 1500 cfm and the 12" model 3680 is 800 cfm. They also the Dual 12" Fan model 3800, which I have, has 1600 cfm which is better than either of the 16" fans. So at least with hayden, they claim two 12" is better than one 16".

Wayne

Two fans only work better if the core is bigger than 20 x 24, otherwise a single 16 inch with a shroud tends to move more air across the face of the radiator.

As for CFM's, the 16 inch SPAL I have been using moves 3000 cfms, when you turn it on while holding it the thing will try to jump out of your hands.

Size 16" pull / Part# 2113*
[2113] $220.00
Size 16" pull / Part# 2113*

Part: 2113*
Size: 16" pull
Blade Type: Skewed
Thickness: 3.65
AMPS: 22.5
Airflow (CFM): 3000

Don