big block cooling issues

[real57vetteguy]

I do have a question for you guys. I am running a Champion 3 core alum radiator, aluminum shroud, and dual 12" fans, my condensor is blocking air flow to the radiator. I can drive the car in stop and go traffic, or on the highway and it runs at 200-205, if i let it sit and idle, for 10+ minutes to simulate being in congested traffic etc it will climb to 215 possibly more. I am trying to figure out a way to mount a pusher fan in front but I am unsure if mounting one to the condensor will work or should I try to sandwich a fan between the condensor and radiator? I think the problem is when the car isnt moving it isnt getting enough air due to the condensor blocking the majority of the front of the radiator.

[CRead01]

I would look at how many cfm your fans are pulling first then see if you can get a higher flowing fan. I am running a lincoln mark viii fan on my big block and it works good.

[astroracer]

A few questions for you...
Are the fans running through a thermostat?
How is the wiring to the fans? Large enough gauge? Are the fans running at full speed?
If you have 3/4 to an inch of space between the rad and condensor you will get enough airflow with the fans running.
Mark

[exwestracer]

How is the hot air getting OUT of the engine compartment? I've run into this issue with A-body Mopars in the past, and there is simply no fix other than to give the air an easier path out from under the hood. If you have an IR thermometer, check the temp at the inlet and outlet fittings of the radiator. With the fans running, you should be seeing a minimum of 50 degrees change across the core. If you are, make sure you don't have a timing or fuel issue at idle. If that is all ok, then I'd REALLY look at the exit paths for the radiator air.

[real57vetteguy]

The radiator is a Champion cooling radiator, 3 core aluminum, dual fans are rated at 880 CFM each, I am running a shroud built specifically for the 12" fans. The wiring is all 10 gauge and brand new, The fans always cut on at 170 degrees, they seem to be moving plenty of air. There is about 1/2 inch between the cond and radiator, They temp sensor is threaded into an intake port. I have done nothing to improve getting hot air out of the engine bay

[carguykeith]

You could just have a fan problem, I was running a single 16" fan that was rated at 2000cfm and was having some cooling issues but upgraded to dual 12" fans rated at 3000cfm and it took care of the problem.

Also is the motor freshly rebuilt? The first few hours mine ran really hot as the rings and bearings broke in.

[SparkyRnD]

you need at least 1/2" of air space between the radiator and the condensor. Your fans may be too small, as 880cfm each x 2 is 1,760cfm. Depending on your engine, that may be well below what you need coupled with only 3 cores.

[real57vetteguy]

you need at least 1/2" of air space between the radiator and the condensor. Your fans may be too small, as 880cfm each x 2 is 1,760cfm. Depending on your engine, that may be well below what you need coupled with only 3 cores.

I found a set of perma cool fans capable of 2300 cfm each. At 88.00 each that might be a good first step?

[real57vetteguy]

You could just have a fan problem, I was running a single 16" fan that was rated at 2000cfm and was having some cooling issues but upgraded to dual 12" fans rated at 3000cfm and it took care of the problem.

Also is the motor freshly rebuilt? The first few hours mine ran really hot as the rings and bearings broke in.

It has about 6k miles on it. Timing and AFR are correct.

[SparkyRnD]

I found a set of perma cool fans capable of 2300 cfm each. At 88.00 each that might be a good first step?

Yes. A stock small block that has good airflow out of the engine compartment can get away with 880cfm fans if the radiator is the right size. But a Big Block needs much more. I would go with the fans as a first step along with a good relay (if you aren't already using one).

Also, without seeing pictures, I have to assume......but make sure that one fan is at the top inlet, and the other is at the bottom outlet. I've seen some people put them opposite, so they don't cool as well. Can you post a picture of your current arrangement installed?

[real57vetteguy]

Yes. A stock small block that has good airflow out of the engine compartment can get away with 880cfm fans if the radiator is the right size. But a Big Block needs much more. I would go with the fans as a first step along with a good relay (if you aren't already using one).

Also, without seeing pictures, I have to assume......but make sure that one fan is at the top inlet, and the other is at the bottom outlet. I've seen some people put them opposite, so they don't cool as well. Can you post a picture of your current arrangement installed?

I will take some pics this evening, but My fans are just the opposite as you suggested.

[sam 74]

1760 cfm for anything other than a stock motor with a big rad is't going to cut it, my single 16 inch fan pulls 2800 cfm with a 2 row aluminum rad and it doesn't go over 200 degrees on a very well built big block.

[SparkyRnD]

I sent you a pm, but if your fans are opposite, then the first thing is to swap that and you should see your temps drop. Reason is this:

if your fans aren't right in front of the inlet / outlet, then you are technically cooling the water mixture only once. If you have the fans right in front of the inlet and the outlet, the water mixture is technically cooled twice: once as it enters the radiator, and second when it leaves the radiator. If the fans are opposite, the water comes in to the radiator, and either go across and gets cooled on the top, then goes out, or it comes into the radiator, goes down and get cooled on the bottom, then goes out back to the engine. If you have them flipped, it gets hit on the way in and the way out. Subtle difference that some people don't consider, but it does make a big difference.

[real57vetteguy]

HMMMM, I didnt get the PM but I understand what you are talking about and it makes perfect sense!

[67 455 Bird ragtop]

but make sure that one fan is at the top inlet, and the other is at the bottom outlet. I've seen some people put them opposite, so they don't cool as well.

Glad I read this. The LT1 setup I was planning to use is also the opposite. I was probably going to need to make a custom shroud to mount them in anyway. So now I can mount them properly.

[SparkyRnD]

HMMMM, I didnt get the PM but I understand what you are talking about and it makes perfect sense!

Sorry, I had someone else PM me about their vette and cooling issues, and I got mixed up. Sorry about the confusion!

Glad I read this. The LT1 setup I was planning to use is also the opposite. I was probably going to need to make a custom shroud to mount them in anyway. So now I can mount them properly.

Yep, it is one of the most overlooked items we see when it comes to electric fan setups and overheating. It is an easy thing to check for and fix.

[SparkyRnD]

Just for fun, I decided today to put the fan issue to the test. I have a radiator in our little shop truck, it's a 351w that has a medium cam, edelbrock intake & carb, headers, and is punched 0.060" over. Down here in Georgia, this is what we call a hot-running truck!

I have two shrouds we made for it, one for dual 12" fans and one for a single 17" fan. First up is the duals:

1. I mounted the two 12" fans and put them in the opposite corners than the inlet and outlet. This means the hot water only passes over one fan before it goes back into the engine. At 55 degrees outside, it crept up to 225 degrees and stayed there.

2. I removed the shroud, and flipped the fans so that they were both at the inlet and outlet. This means the hot water gets cooled as it enters the radiator, then gets cooled again before it leaves. I started the truck back up after it cooled down. At 55 degrees outside, it crept up to 212 degrees and stayed there. Note that this gave a 13 degree difference at the intake port where the temperature sending unit is.

3. I removed the shroud, and installed the single high output 17" fan that sits in the center of the radiator. I didn't let the engine cool down, and fired it up immediately. The temperature was at 220 degrees when I started the engine (temperature goes higher as soon as you turn off the engine AND fans as the coolant is no longer circulating). At 55 degrees outside, with the fan on, it instantly dropped down to 182 degrees and stayed there.

That is 43 degrees of difference on a hot-running engine by using a high end, single 17" fan versus the pair of 12" fans in the wrong locations; and that is 30 degrees of difference on a hot-running engine using two regular 12" fans in the correct locations versus a high-end, single 17" fan.

All of the temperatures were on a gauge using a probe in the intake manifold, and temps were also verified using a laser thermometer. Engine temps and gauge temps were within 1-2 degrees of each other. The whole point of this exercise is to make sure people understand the principles involved with cooling at IDLE (cooling at speed is a whole different animal), and how placement of fan, size of fan, quantity of fans, and regular versus high-output fan can mean the difference between an overheated engine, or a nice and cool engine.

With regards to the 12" fans, they are a private label we have used for the last half-dozen years and were installed on another project vehicle that has a small block that is stock, using one of our radiators, and it keeps it between 185 and 190 all day long, so we know that the fans work and do their job. I wanted to put it all on this .060" over 351w as I know it's a very hot running set up with a thin waterjacket, just to prove a point.

[MonzaRacer]

Honestly I see people having cooling issues all the time and wonder how I cooled my 402. 10.5 to 1 compression on premium unleaded, lots of timing and well tuned.
I had a three row A body rad in copper and brass in my 70 Monte, ran a 91 Cavalier 4 cyl cooling fan and used a Chrysler temp sensor that screwed into the right side head. came on at like 180 I think shut off at 170, but I would need to recheck the specs been almost 20 yrs since I did it. Car never got hot, one fan. I see so many people fussing around on these cooling systems and I never had issues. One car I had issues with was a 71 sbc Monte with an aluminum shroud and fan that fit the rad, worst POS set up ever. did away with the shroud and it ran much cooler.
But as some say it IS about getting cool air in and hot air out. Never had an issue with fan placement on standard single pass rads. Reason the single pass operate is the suction at bottom of outlet tank causes hot zone to run at a partial slant, there is some actual movement in cold zone corners but less than you think.
Also if your having temp issues what are the ACTUAL highest temps you get as 215 is NOT hot. I honestly run my cars hotter as it reduces wear and if properly tuned you make MORE power. again PROPERLY tuned.
Look at current car tech, factory cars are running well over 200 degrees before turning fans on and making 400 to 500 hp.
A simple fix for cars that run hot and LIKE to boil over switch too Evans NPG+ coolant, then you never have to worry about over heating again as it boils at 375F deg. with no pressure. www.evancooling.com

[tommycomfort]

Just for fun, I decided today to put the fan issue to the test. I have a radiator in our little shop truck, it's a 351w that has a medium cam, edelbrock intake & carb, headers, and is punched 0.060" over. Down here in Georgia, this is what we call a hot-running truck!

I have two shrouds we made for it, one for dual 12" fans and one for a single 17" fan. First up is the duals:

1. I mounted the two 12" fans and put them in the opposite corners than the inlet and outlet. This means the hot water only passes over one fan before it goes back into the engine. At 55 degrees outside, it crept up to 225 degrees and stayed there.

2. I removed the shroud, and flipped the fans so that they were both at the inlet and outlet. This means the hot water gets cooled as it enters the radiator, then gets cooled again before it leaves. I started the truck back up after it cooled down. At 55 degrees outside, it crept up to 212 degrees and stayed there. Note that this gave a 13 degree difference at the intake port where the temperature sending unit is.

3. I removed the shroud, and installed the single high output 17" fan that sits in the center of the radiator. I didn't let the engine cool down, and fired it up immediately. The temperature was at 220 degrees when I started the engine (temperature goes higher as soon as you turn off the engine AND fans as the coolant is no longer circulating). At 55 degrees outside, with the fan on, it instantly dropped down to 182 degrees and stayed there.

That is 43 degrees of difference on a hot-running engine by using a high end, single 17" fan versus the pair of 12" fans in the wrong locations; and that is 30 degrees of difference on a hot-running engine using two regular 12" fans in the correct locations versus a high-end, single 17" fan.

All of the temperatures were on a gauge using a probe in the intake manifold, and temps were also verified using a laser thermometer. Engine temps and gauge temps were within 1-2 degrees of each other. The whole point of this exercise is to make sure people understand the principles involved with cooling at IDLE (cooling at speed is a whole different animal), and how placement of fan, size of fan, quantity of fans, and regular versus high-output fan can mean the difference between an overheated engine, or a nice and cool engine.

With regards to the 12" fans, they are a private label we have used for the last half-dozen years and were installed on another project vehicle that has a small block that is stock, using one of our radiators, and it keeps it between 185 and 190 all day long, so we know that the fans work and do their job. I wanted to put it all on this .060" over 351w as I know it's a very hot running set up with a thin waterjacket, just to prove a point.

This is flat out great information! I printed it so I can reference it in future when I install fans.

[real57vetteguy]

Its been a while, work has been so busy. I did switch the fans around as suggested, it helped a little but I think I still have an issue. I know I should go up in fan size, and I will do that, I want to make SURE I have no cooling issues for next year, I am going to be pulling the 500 mile engine to make some minor adjustments and while its out considered getting a FlexKool high volume water pump, will this help with my cooling issues??